Chemistry 12J

12 ChemistryAuthorsHans van Kessel St.Albert ProtestantSchools Dr. Franklenkins University of Alberta LucilleDavies Limestone District SchoolBoard DonaldPlumb The Bishop StrachanSchool Maurice Di Giuseppe Toronto Catholic District SchoolBoard Dr. Oliver Lantz University of Alberta DickTompkins EdmontonPublic SchoolBoard

ProgramConsultant Maurice Giuseppe DiToronto Catholic District SchoolBoard

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NelsonChemistry12 Authors H a n sv a n K e s s e lD r . F r a n kJ e n k i n s , , L u c i l l e a v i e sD o n a l dP l u m b , D , M a u r i c eD i G i u s e p p eD r .O l i v e rL a n t z , , D i c kT o m p k i n s Contributing Writer MilanSanader

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National Libraryof Canada Cataloguingin PublicationData M a i n e n t r y u n d e rt i t l e : 1 Nelson hemistry 2 c

-" ',i;:,ifiW,,o 6 ta l+5'5 ot-l1.Chemistry. l . J e n k i n sF r a n k ,1 9 4 4 , 2002 QD33.Nrt42 c2002-900872-7 540

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Unit 1 AreYou Ready?

4

Ghapter1 OrganicGompounds1.1 1.2 1.3 1.4 FunctionalGroups Hydrocarbons Reactionsof Hydrocarbons Organic Halides Explore an lssue Can We Afford Air Conditioning? 1.5 1.6 1.7 1.8 1.9 Alcohols and Ethers Aldehydesand Ketones CarborylicAcids and Esters AminesandAmides SynthesizingOrganicCompounds Lah Activities Lab Exercise 1.3.1 PreparationofEthyne Investigation 1.5.1 Comparison of Three Isomersof Butanol Investigation 1.5.2 Trendsin Propertiesof Alcohols Investigation 1.7.1 Propertiesof CarboxylicAcids Activity 1.7.2 Synthesis Esters of Activity 1.9.1 Building Molecular Models to Illustrate Reactions ActiYity 1.9.2 Preparationof an Ester-Aspirin Chapter I Summary Chapter I Self-Quiz Chapter I Review

68 11 24 32 35 38 49 58 69 80

Explore an lssue Will that be"Regular" "Diet"? or 2.5 Starch Cellulose- Polymers Sugars and of 2.6 NucleicAcids 2.7 FatsandOils Careercin Chemistry Lab Activities Investigation2,l,l Identification Plastics of Activity2.1.2 MakingGuarGum Slime Investigation2.2.l Preparation Polyester-aCondensation of Polymer Activity2.7.l MakingSoap Chapter2 Summary 2 Chapter Self-Quiz Chapter2 Review Unit 1 PerformanceTask:Chemistry in a Bath Tub Unit 1 Self-Quiz Unit 1 Review

t2r125

r29 133 r37

138 140

t4r r43 r44 r45 r46 148 150 152

84

87 89

Unit 2 Are You Ready?

158 160 t62 r67 r69t74 181 185 199 203 207

Chapter3 Atomic Theories90 92 95 96 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 EarlyHistoryof AtomicTheories CaseStudy Nuclear Scientist A Canadian Originsof QuantumTheory Theory TheBohrAtomic QuantumNumbers AtomicStructure the Periodic and Thble Wave Mechanics Orbitals and Applications QuantumMechanics of Careers in Chemistry Lah Activities Investigation 3.1.1 TheNatureof Cathode Rays

Ghapter2 Polymers-Plastics, Nylons,and Food2.1 SyntheticAdditionPolymers 2.2 Synthetic Condensation Polymers 2.3 Case Study An Eyefrrl Polymers: of Lenses Contact 2.4 Proteins-NaturalPolyamidesvi Contents

98 100 108 IL4 I17

Activity 3.1.1 Rutherford'sGold Foil Experiment Activity 3.3.1 Hot Solids Investigation 3.3.1 The PhotoelectricEffect Activiry 3.4.1 Line Spectra Activiry 3.4.2 The Hydrogen Line Spectrum and the Bohr Theory Investigation3.5.1 Paramagnetism Lab Exercise3.6.1 Quantitative Paramagnetism Activity 3.7.1 Modelling StandingElectronWaves ActiYity 3.7.2 Simulation of Electron Orbitals Chapter 3 Summary Chapter 3 Self-Quiz Chapter 3 Review

210 210211

Investigation 4.6.1 Classifoing Mystery Solids Chapter4 Summary Chapter Self-Quiz 4 Chapter4 Review Unit 2 PerformanceTask A Study of an Element Unit 2 Self-Quiz

279 280 281 282

2t2

284

2a6 2Aa

2r3 214 2t5 216

Unit 2 Review

Unit 3 AreYou Ready? 2r7 2t8 2t9 220

294

Ghapter5 Thermochemistry5.1 5.2 5.3 5.4 5.5 5.6 Changes Matter and Energy in Molar Enthalpies Enthalpy Changes Representing Hess's Law of Additivity of Reaction Enthalpies StandardEnthalpiesof Formation The EnergyDebate Exptore an Issue EnergyOptions Lab Activities Investigation5.1.1 Medical Cold Packs Investigation 5.2.I Molar Enthalpy of a Chemical Investigation 5.3.1 Combustion of Alcohols Investigation 5.4.1 Hess's Law Lab Exercise5.5.1 TestingEnthalpiesof Formation Chapter 5 Summary Chapter 5 Self-Quiz Chapter 5 Review

296298 306 313 322 33r 341 345

Ghapter4 GhemicalBonding4.1 4.2 Lewis Theory of Bonding The Nature of the ChemicalBond Case Stady The StrangeCaseof Benzene 4.3 VSEPRTheory Explore an lssue Linus Paulingand theVitamin C Controversy 4.4 4.5 4.6 Polar Molecules Intermolecular Forces The Structure and Propertiesof Solids

222224 231 24r 242

250 25r257 268 275

348 349 351 352 354 355 356

Carcers Ckemistry ix LahActivitiesActivity 4.3.1 Shapes Molecules of Investigation 4.4.1 Testingfor Polar Molecules Lab Exercise 4.5.1 Boiling Points and Intermolecular Forces Investigation 4.5.1 Hydrogen Bonding

278

Contents vii

Kinetics Chapter6 Ghemical6.1 6.2 6.3 6.4 6.5 Rateof Reaction FactorsAffecting ReactionRate

358 360

7.4

367 RateLawsand Order of Reaction 372 Theory and Rateof Reaction Collision 383 Explaining andApplying ChemicalKinetics 392Explore an lssue Food Preservation Careers in Chemistry Lah Activities Lab Exercise 6.1.1 Determining a Rateof Reaction Investigation6.2.1 Chemical Kinetics and FactorsAffecting Rate Investigation6.3.1 The Iodine Clock Reaction Lab Exercise6.4.1 The Sulfur Clock Activity 6.5.1 Catalysts Industry and Biochemical in Systems

Case Study The Haber Process: ProducingAmmonia for Food and Bombs in Quantitative Changes Equilibrium Systems The Solubility Product Constant Energyand Equilibrium: The Lawsof Thermodynamics Explore an lssue Can We Do Anything About Pollution? Lah Activities InvestigationT.l.l Discoveringthe Extent of a Chemical Reaction Lab Exercise7.2.1 Developingan Equilibrium Law Expression InvestigationT.3.l TestingLe Chatelier'sPrinciple InvestigationT.6.l Determining the Kro of Calcium Oxalate InvestigationT.6.2 Determining Kro for Calcium Hydroxide

46r463 482 494 501

7-5 7.6 7.7

397 398

401

513

402 403404

5I4 5I4 5I7 519 520 522 523

405 406 407 408

Chapter 6 Summary Chapter 6 Self-Quiz Chapter 6 Review Unit 3 Performance Task: Energy and Rates Analysis of Chemical Reactions Unit 3 Self-Quiz Unit 3 Review

Chapter 7 Summary Chapter 7 Self-Quiz Chapter 7 Review

Ghapter Acid-BaseEquilibrium 8410 412 414 8.1 8.2 8.3 8.4 8.5 The Nature of Acid-BaseEquilibria WeakAcidsand Bases Acid-BaseProperties SaltSolutions of Acid-BaseTitration Buffers Case Sfudy The Science Acid Deposition of

5126528 551 581 595 615 621 624 625

Unit 4 Are You Ready?

420

Explore an lssue Acting to Reducethe Effects Careers in Chemistry Lah Activities Activity 8.1.1 Determining the pH of Common Substances Investigation8.3.1 The pH of SaltSolutions

Chapter7 ChemicalSystemsin Equilibrium

422

7.1 DynamicEquilibriumin Chemical Systems 424 7.2 EquilibriumLawin Chemical Reactions 439 7.3 Qualitative Changes EquilibriumSystems450 in

626 627

viii

Contents

Activity 8.4.1 Titration Quantitative Investigation 8.5.1 BufferAction Chapter Summary 8 Chapter Self-Quiz 8 Chapter8 Review Unit 4 Performance Task:Chemical Analyst for a Day Unit 4 Self-Quiz Unit 4 Review

627 629 630 631 632

Investigation 9.5.1 InvestigatingGalvanicCells Investigation9.6.l The Corrosion of Iron Chapter 9 Summary Chapter 9 Self-Quiz Chapter 9 Review

722 723 724 725 726 728 730 737 742 745 747

Gells Chapter10 Electrolytic634 636 639 10.1 Electrolysis 10.2 Science and Technologyof Electrolysis Explore an lssue The Casefor and Against Chlorine Careers in Ghemistry 1O.3 Stoichiometry Cell Reactions of Lab Activities Investigation10.1.1 A PotassiumIodide Electrolytic Cell Investigation10.1.2 Electrolytic Cells InvestigatingSeveral Investigation 10.3.1 Investigatingan Electrolytic Cell Chapter l0 Summary Chapter l0 Self-Quiz Chapterl0 Review 694 695 7t0 Unit 5 Performance Task: Electroplating Unit 5 Self-Quiz Unit 5 Review 715 716 716 7t7 7t8 7t9

Unit 5 Are You Ready?

648

754 755 756 758 759 760 762 764 766

ChapterI9.1 9.2 9.3 9.4

ElectricGells

650652 664 674

Oxidation and Reduction BalancingRedoxEquations Predicting RedoxReactions Technology Cellsand Batteries of Explore an Issue Hydrogen Fuel Cells

68s

9.5 9.6

GalvanicCells Corrosion Lab Activities Investigation 9.1.1 SingleDisplacementReactions Lab Exercise 9.1.1 Oxidation States Vanadium of Investigation 9.3.1 Spontaneityof RedoxReactions Lab Exercise 9.3.1 Building a RedoxTable Investigation9.3.2 The Reactionof Sodium with Water Activity 9.4.1 Developingan Electric Cell Lab Exercise9.4.1 Characteristics a Hydrogen Fuel Cell of Activity 9.5.1 GalvanicCell Design

Inquiry Appendix Scientific A: AppendixB: Safety AppendixC: Reference 11 AppendixD: Chemistry Review AppendixE:Answers Glossary Index Credits Periodic Table

772 790 796 805 816 820 828 836 838

720721

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Contents ix

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Eugenia Kumacheva Associate Professor University Toronto of "By clever slnthesis, organic chemists obtain new molecules

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and architectures, compositions, functions. with fascinating polymers(long-chain molecules groupstudies My research fluorescent, nonunits) that possess manyrepeating with properties. particular, In we linearoptical,and electroactive madefrom very materials interested nanostructured in are we For smallpolymerparticles. example, work on syntheOne polymers high-density for opticaldatastorage. of sizingthe materialsdesignedand createdin our laboratory is often pictured asa piece of new plastic about the sizeof a cube of sugar on which one can store the entire Canadian National Library collection. Other polymers can changetheir transparencywhen illuminated with high-intensity light. The coatings and films made from suchpolymers can be usedto protect pilots'eyesfrom damaging laserlight and in optical networks in telecommunication. New synthetic polymers have found a variety of exciting applications, and their use in materials sciencewill grow even more rapidly in the future."

) Overall ExpectationsIn this unit, you will be able to . demonstrate understandingthe structure various and organic compounds, of of of an these compounds; chemical reactions involving r investigate predict through and various organic compounds research experimentation, of and and represent structures organic the the products organic of reactions, name and compounds using IUPAC the system molecular and models; o evaluate impact organic andthe compounds ourstandard living on of the of envtronmenl.

g UnderstandinConcepts1 Write the IUPACnamefor eachof the following compounds.(a) CH2CH3

(b)

) FrerequisitesConcepts . IUPAC nomenclature of simple aliphatic hydrocarbons, including cyclic compounds r Structural geometric and isomers r Characteristic physical properties chemical and reactions saturated of and unsaturated hydrocarbons o Electronegativity polar and bonds o Chemical bonding, including ionicbonds, covalent bonds, hydrogen bonds, der van Waals forces o Formation solutions of polar involving and nonpolar substances

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Draw structuresof the following compounds. (a) pentane (b) 2,2-dimethylheptane (c) 4-ethyl- I -methylcyclohexane (d) 5-methyl-1-hexene (e) 1-butyne

3 . Write a balanced chemical equation to show the complete combustion ofheptane,a component of gasoline. 4 . Which of the following are structural isomers? ( a H.

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Predict the relative boiling points of the following two compounds' (a) CHTCHTCH2CH2CH3 Pentane

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ICH, 2,2-dimethYlProPane in 6. Predictthe relativesolubilitiesof the following compounds water. ( b ) H H H ( a ) H H \ / | l l H , Ca' . " t H-C-C-H tC/ rrt "

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carbon, electronegativity: in Write the following elements order of increasing nitrogen,oxygen'sulfur. hydrogen, chlorine, the describe intramolecularbondtypes For eachof the following compounds, forces. and the intermolecular (a) CH, (b) H2o (c) NH3

ApplyinglnquirySkillsof bromine (Figure l). Samples the soluwith aqueous 9. Threeliquids aretested is The evidence points determined. tions arealsovaporizedand their boiling shownin Table1. Table1Gompound Brrr".rtest pointCC) boiling Liquid 1 no change 36 Liquid 2 turns colourless Liquid 3 no change -12

39

and Which of the liquids is pentane,2-methylbutane, 2'methyl-2-butene?

Safety and TechnicalSkillsof and in needed the handling,storage, disposal 10. List the safetyprecautions (a) concentrated sulfuricacid; (b) flammableliquids,e.g',ethanol.

Figure I

Chemistry 5 Organic

5 In this chapter, - you will be able to. classify compounds organic by identifying functional their groups, name,by by and by structural formula, models; building molecular r usethe IUPAC system to nameandwritestructural diagrams different for classes organic of compounds, identify and somenonsystematic names forcommon organic compounds; . relate somephysical properties the classes of of to organic compounds their groups; functional r describe predict and characteristic chemical reactions different of classes of organic and compounds, classify chemical the reactions type; by e design synthesis the of organic compounds from simpler by compounds, predicting products the of organic reactions; r carryout laboratory procedures synthesize to organic compounds; r evaluate useofthe term the "organic" everyday in language in scientific and terminology; r describe variety the and importance organic of compounds ourlives, in and evaluate impactof the organic materials our on standard living of andthe environment.

In a supermarket or in a pharmacy, the term "organic" is used to describe products that are grown entirely through natural biological processes, without the use of synthetic materials."Organic" fruits and vegetables not treated with synthetic fertilizers or pesare ticideq "organic" chickensor cows are raisedfrom organically grown feed,without the use of antibiotics. The growing "organic" market, despite higher prices over "conventionally grown" foods, indicates that some consumers believe that molecules made by a living plant or animal are different from, and indeed better than, those made in a laboratory. In the early 18th century, the term "organic" had similar origins in chemistry. At that time, most chemists believed that compounds produced by living systemscould not be made by any laboratory procedure. Scientistscoined the chemical term "organic" to distinguish between compounds obtained from living organisms and those obtained from mineral sources. In 1828,a German chemist, Friedrich Wdhler. obtained urea from the reaction of two inorganic compounds, potassium cyanateand ammonium chloride. Sincethen, many other organic compounds have been prepared from inorganic materials. Organic chemistry today is the study of compounds in which carbon is the principal element. Animals, plants, and fossil fuels contain a remarkable variety of carbon compounds. What is it about the carbon atom that allows it to form such a variety of compounds, a variety that allows the diversitywe seein living organisms?The answer lies in the fact that carbon atoms can form four bonds. Carbon atoms have another special property: They can bond together to form chains,rings, spheres, sheets, and tubes of almost any sizeand can form combinations of single, double, and triple covalent bonds. This versatility allows the formation of a huge variety of very large organic molecules. In this chapter,we will examine the characteristicphysical properties of families of organic molecules,and relate theseproperties to the elementswithin the molecule and the bonds that hold them together.We will also look at the chemical reactions that transform one organic molecule into another.Finally,we will seehow thesesingletransformations can be carried out in sequence synthesize desiredproduct, starting with simple compounds. to a

Much of the research organic in chemistry focused a search newor is on for products. improved Suppose you wishto develop new stainremover, a more that a or effective drug,or a better-tasting drink.Whatshouldbe the properties the soft of product? ingredients yourchosen of In the fieldof biology, complex systems havebeendeveloped classify name to and the countless different livingorganisms. Suggest effective an method classifying of and naming vastrangeof organic the compounds exist. that Fromyourknowledge intramolecular intermolecular of and attractions, describe featuresin the molecular structure a compound wouldaccount its solubilitv of that for points. and its melting boiling and Whatdoes"organic" mean? Give many as definitions youcan. as

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How Do Fire-Eaters Do That?you everwondered somestreetperformers extinguish a Have how can Hereis flaming torchby "swallowing" fire,withoutburning the themselves? af an activity that mighthelpyou answer puzzle "howdo theydo that?" the (rubbing alcoholJ; water; Materials:2largeglassbeakers jars;2-propanol or tablesalt;tongs;paper; safety lighter match or 2-propanol is highly flammable.Ensurethat containersof the alcohol are sealed and stored far from any open flame.

equalvolumes 2-propanol In a largeglassbeaker jar,mixtogether or of to and water, a totalof about100mL. amount NaCl(about g) in the solution, add 0.5 to Dissolve small a of colour the flamethat will be observed. to 5 Using tongs, a piece paperabout cm x 5 cm intothe solution dip of out until it is well soaked. the Take paper and hold it overthe jar for a few seconds until it stopsdripping. it Dispose the alcohol of solution flushing downthe sink(oras by directed yourteacher), fill another by beaker jar with wateras a or and precautionary measure extinguish flamesif necessary. to any paperwith it Stillholding soaked the tongs, ignite using lighter the or match. a why "fire-eaters" not do suggest reason [aJ Fromyourobservations, suffer severe burnsfromtheirperformance.

O r g a n iC o m p o u n d s c 7

Figure I Thedesignand synthesis new of properties, materials with specific likethe olastic this artificial in ski run,is a keyfocusof the chemical industry. organic family a groupof organic compounds with common structural features that imoartcharacteristic physical properties reactivity and functional group a structural arrangement atoms of that imparts characteristics the oarticular to molecule

With the hugenumberof organicsubstances, would have we greatdifficultymemorizing the propertiesof eachcompound. Fortunately,the compoundsfall into organic families according particularcombinations atomsin eachmolto of properties reactivityof the compounds ecule. physical The and arerelatedto theserecognizable combinations, calledfuncgroups.Thesefunctional groupsdeterminewhether tional the molecules readilysolublein polar or non-polar solare vents,whether they havehigh or low melting and boiling points,and whetherthey readilyreactwith other molecules. So,if we can recognize and understandthe influenceof eachfunctionalgroup,we will be ableto predictthe propertiesof anyorganiccompound.If we canpredicttheir properties,we canthen designmolecules serveparticularpurposes, devise to and methods to makethesedesired molecules. In this chapter, will discuss we eachorganicfamily by relating its propertiesto the functionalgroupsit contains. Moreover, will focuson how oneorganicfamily canbe we synthesized from another;that is, we will learn aboutthe reactionpathways that allow onefunctionalgroup to be transformedinto another. the end of the chapter, will By we havedeveloped summaryflow chart of organicreactions, we will be ableto plan a and syntheticpathways and from manydifferent organicmolecules. to After all, designing the synthesis newmolecules, of rangingfrom high-techfabricsto "designer drugsj'is oneof the most important aspects modern organicchemistry(Figure l). of Beforediscussing eachorganicfamily let'stake a look at what makesup the functional groups. Althoughtherearemanydifferentfunctionalgroups, theyessentially consist of only threemain components, or more of which may be presentin each one functionalgroup.Understanding properties these the of threecomponents makeit will easy understand propertiesof the organicfamiliesto which to and predict the general theybelong(Figure2): -C:C- or -C=C' carbon-carbonmultiplebonds, . singlebondsbetween carbonatom and a more electronegative a atom, e . 9 .-,C - O - , - C - N - , o r - C - C l . carbonatom double-bonded an oxygenatom, -C:O to(a)

H HC:

H C-H

(b)

H

IH-C-O-H

Figure 2 Examples the threemaincompoof groups: nentsof functional (a) A doublebondbetween two carbonatoms (b) A singlebondbetween carbon and a moreelectronegative atom(e.9., orygen) (c) A doublebondbetween carbon ano oxygen 8 Chapter 1

ethene(analkene)

IH (an methanol alcoholJ

(c)

H

IH-C:O(an methanal aldehydeJ

Section 1.1

Carbon-CarbonMultiple BondsWhen a C atom is single-bonded another C atom, the bond is a strong covalentbond to that is difficult to break.Thus, the sitesin organic moleculesthat contain C-C bonds are not reactive.However,double or triple bonds between C atoms are more reactive. The secondand third bonds formed in a multiple bond are not as strong asthe first bond and aremore readilybroken.This allowscarbon-carbon multipie bonds to be sitesfor reactions in which more atoms are addedto the C atoms.The distinction betweensingleand multiple bonds is not alwaysclear-cut. For example, the reactivity of the six-carbon ring structure found in benzeneindicates that there may be a type of bond intermediate betweena singleand a double bond. This theory is supportedby measured bond lengths. You will iearn more about the strengthsof singleand multiple bonds in Chapter 4.When atoms havedifferentelectronegativities [Table 1), the bondsthat form betweenthem tend to be polar.with the electrons disolaced toward the more electronegative atom.Many properties of compoundsof these elements are explained by the polarity of their bonds. Table I of Electronegativities CommonElements

Single Bonds BetweenCarbonand More Electronegative AtomsWhenever a C atom is bonded to a more electronegative atom, the bond between the atoms is polar; that is, the electronsare held more closeiyto the more electronegative atom. This results in the C atom having a partiai positive charge and the O, N, or halogen atom having a partial negativecharge.Any increasein polarity of a molecule also increases intermolecular attractions,such as van der Waals forces.As more force is required to separatethe molecules, the melting points and boiling points also increase(Figure 3).

1

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Figure 3 (a) Nonpolar substances, with weakforcesof attraction the evapoamong molecules, In rateeasily. fact,theyare at oftengases roomtemperature. (b) Polar with substances, strong amongthe forcesof attraction considerable require molecules, to energy evaPorate.

If the O or N atoms are in turn bonded to an H atom, an -OH or -NH group is formed, with specialproperties. The presenceof an -OH group enablesan organic molecule to form hydrogen bonds with other -OH groups. The formation of these hydrogen bonds not only further increases intermolecular attractions, it also enables thesemoleculesto mix readilywith polar solutesand solvents. You may recallthe saying "like dissolves like." The solubility of organic compounds is affectedby nonpolar components and polar components within the molecule. SinceN is only slightly lesselectronegativethan O, the effect of an N-H bond is similar to that of an O-H bond: -NH groups alsoparticipate in hydrogen bonding.

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C Organic ompounds I

DoubleBonded Garbon and OxygenThethird main component functionalgroupsconsists a C atom double-bonded of of to an O atom.The doublecovalent bond between and O requiresthatfour electrons C be shared between atoms, four beingmorestronglyattracted the O atom.This makes the all to the C:O bond stronglypolarized, with the accompanying effects raisingboiling and of meltingpoints,and increasing solubilityin polarsolvents.

Three Main Components of Functional GroupsMultiple bonds betweenC atoms -C:CUnlike single C-C bonds, double and triple bonds allow atoms -C=Cto be added to the chain.C atom bonded to a more electronegative atom (O, N, halogen)

c-oC-N C-Cl, C-Br, C-P C-OH or C-NH_

Unequal sharing electrons of results polarbonds, in increasing intermolecular attraction,and raisingboiling and meltingpoints. These groupsenable hydrogen bonding,increasing solubility in polarsubstances.

C atom double-bondedto an O atom C:O Theresulting polarbond increases boilingpoint andmeltingpoint.

UnderstandingGoncepts l. Explain meaning the term"functional the group." of 2. Are doubleandtriplebondsbetween atomsmorereactive C orlessreactive than single bonds? Explain. 3. Woulda substance composed morepolarmolecules of havea higher lowerboiling or pointthan a substance composed lesspolarmolecules? of Explain. 4. Describe threemaincomponents functional the groupsin organicmolecules. of

Understanding Concepts 1. Whatis the effectof the presence an -OH groupor an of -NH groupon (a) the melting and boilingpointsof the molecule? Explain. (bl the solubility the molecule polarsolvents? of in Explain. 2. ldentify components functional all groupsin the folof lowingstructural diagrams. Predict solubility each the of substance water. in (a) CH'-O-H [b) cHscH:cHcH3 (cl CH'CH:O (dJ CH3CH'C:O I OH

3. Thecompounds water, ammonia, methane formed and are when an oxygen atom,a nitrogen atom,and a carbonatom eachbondswith hydrogen atoms. (aJ Writea formula eachof the threecompounds. for with reference electronegativities interto and [b) Predict, molecular forces, solubility eachof the comthe of pounds the others. in (cJ Of the threecompounds, identify whicharefoundor produced livingorganisms, classify by and eachcompoundas organic inorganic. youranswer. or Justify

10 Chapter 1

We will begin our study of organicfamilieswith a reviewof hydrocarbons,many of which containmultiple bondsbetween carbonatoms,a functionalgroup with characteristicproperties. of Fossilfuels(Figure l) containmainly hydrocarbons: simplemolecules hydrogen These from longago. andcarbonthat arethe resultof thebreakdown living organisms of compounds includethe naturalgasthat is pipedto our homes, propanein tanksfor the barbecues, the gasolinefor our cars.Hydrocarbons classified the kinds of and are by carbon-carbon bondsin their molecules. alkanes,all carbonsarebondedto other In Figure I bonds,resulting the maximumnumberof hydrogen atomsbondedto atomsby single in of Crudeoil is madeup of a variety Alkenes are eachcarbonatom.These molecules thus called are saturated hydrocarbons. potentially usefulhydrocarbons. hydrocarbons containoneor morecarbon-carbondoublebonds,andalkynesconthat tain one or more carbon-carbon triple bonds.These two groupsarecalledunsaturated lrydrocarbons because containfewer they numberof hydrogen thanthemaximumpossible compound ways. hydrocarbonan organic Because and atoms. alkenes alkpes have multiplebonds, theyreactin characteristic and thatcontains carbon only The multiple bond is the functionalgroup of these two chemical families. hydrogen atomsin its molecular In all of these hydrocarbons, carbon-carbonbackbone mayform a straightchain, the structure (Tablef ). All of these molechains, a cyclic (ring) structure oneor morebranched or culesareincludedin a group calledaliphatic hydrocarbons. with alkane a hydrocarbon only is A hydrocarbon branchthat is attached the main structureof the molecule called singlebondsbetween to carbonatoms it an afkyfgroup.When methaneis attached the main chainof a molecule, is called to that a methyl group, -CH:. An ettrylgroup is CH3CH2,the branch formed when ethane alkene a hydrocarbon contains double at least onecarbon-carbon links to anotherchain.general CrHr, bond; formula,

TableI

ExamplesHydrocarbons ofExample Formula Spacefill diagram Bondand angles diagram that alkyne a hydrocarbon contains triple at least onecarbon-carbon formula, Cr{zn-z bond;general cyclic hydrocarbona hydrocarbon havea closedring whosemolecules structure aliphatic hydrocarbona compoundthat hasa structure based on chainsor rings or straight branched doesnot include of carbonatoms; suchas benaromatic compounds zene group alkyl group a hydrocarbon froman alkaneby the derived atom;oftena removal a hydrogen of groupor branch an on substitution molecule organic

ydrocarbon

sroupAliphatic alkane ethane

cH3cH3

&4

cyclohexaneCoHrz

alkene

ethene

cHzcH2

,,(M,::}*@*t:,

alkyne Aromatic

ethyne

CHCH

benzene

coHo

ts{ { P

,,'P4,,,,'Compoundst 1 Organic

aromatic hydrocarbona compoundwith a structure basedon benzene: ring of six carbonatoms a IUPACInternational Unionof Pure andApplied Chemistry; organithe zationthat establishes conventhe tionsusedby chemists

A fourth groupofhydrocarbons with characteristic properties structures called and is the aromatic hydrocarbons. The simplestaromatichydrocarbonis benzene; other all membersof this family are derivatives benzene. of The formula for benzene C6H6, is and the six carbonatomsform a uniquering structure.Unlike ryclohexane, CuH,r,the (Table1).As we will learn benzene ring hasa planar(flat) structure,and is unsaturated Iaterin this chapterand in Chapter10,the bondsin the benzene haveproperties ring intermediatebetween singlebondsand doublebonds;the common structuraldiagramfor benzene showsa hexagon with an inscribedcircle,symbolizingthe presence double of bondsin unspecified locations within the six-carbon ring (Figure2). The uniquestructure and properties compounds of containingbenzene rings havepromptedtheir classificationasa broad organicfamily of their own. Namedhistoricallyfor the pleasant aromasof compounds suchasoil of wintergreen, aromaticcompounds includeall organicmolecules that containthe benzene ring. All other hydrocarbons and their oxygenor nitrogenderivatives that arenot aromaticarecalledaliphaticcompounds.

Eigure2 Benzene, C6H6, colourless, is flammable, toxic, andcarcinogenic, and hasa pleasant odour. melting lts pointis 5.5oC its boiling point and 80.1"C. is widely lt usedin the manufacture plastics, of dyes, synthetic rubber, drugs. and

Nomenclatureof HydrocarbonsBecause therearesomanyorganiccompounds, systematic a methodof namingthem is essential. this book, we will usethe IUPAG In system nomenclature, of with additional nonsystematic names that you may encounter commonusage. is especially in It important to havea good graspof the nomenclature hydrocarbons, the namesof many of as organicmolecules based thoseof hydrocarbon are on parentmolecules.

AlkanesJoinedBenzene Rings Like otherhydrocarbons, benzene rings can link togetherto form a wide variety of compounds (Figure 3), many of which are quite sme\!(a)

(b) rarArA VVVFigure 3 (a) Naphthalene, C.,oHr, a colouris lesssolidwith a pungent odour. pointis 80"C, Its melting and its boilingpoint218oC. However, it sublimes heating. is the on lt maincomponent mothballs, of and is alsousedas an insecticide,in solvents, in the synand thesis dyes. of (b) Anthracene, C'oH16,a colouris lesssolidwith melting and points 218oC boiling of and 354"C. is lesswell known, lt but is alsousedin the synthesis of dyes. 12 Chapter I

AII alkanes namedwith the suffix-ane. are The prefix in the nameindicates number the of carbonatomsin the longest straightchainin the molecule(Table2). Thus a 5-C straight-chained alkanewould be namedpentane. Any alkylbranches the carbonchainarenamedwith the prefix for the branch,folin Iowedby the suffix -71. Thus,a branchthat contains a2-C chainiscalledan ethylgroup. Thenameof a branched alkane must alsoindicate point of attachment thebranch. the of Thisis accomplished byassigning numbers each atomof theparentalkane, pointing to C and out thelocationof thebranchchainby thenumeralof theC atomwhere branching the occurs. Thenamingqntemalwapuses lowest the numbers possible denote positionon thedrain. to a Finally, numerals separated commas; all are mrmerals letters separated hyphens; by and are by andnames ofbranches parentchains not separated. and are

Table 2 Alkanes and Related AlkylGroups Prefix metheth-

IUPAC name methane ethane propane butane pentane nexane heptaneoctane

FormulaCH4Gt

Alkyl group methylethylpropylbutylpentylhexylheptyloctylnonyldecyl-

Alkyl formula -cHg - CzHs - CsHz- CoHt

CzHorot csHato) c+HroG) CsH''ztD CoHrr,0l czHro(ll CaHra(t) csHzo(ll croHzz(ll

propbutpenthexheptoct-

-csHrr -ceHrs- CzHru

nondec-

nonanedecane

- ceH rz - cnHrs - croHzr

Section1.2

We will take a special look at naming propyl groupsand butyl groups.When alkyl groupshavethree or more C atoms,they may be attached a parent chain either at to their end C atom,or at oneof the middle C atoms.For example, Figure4 shows points two for of attachment a propyl group.The two arrangements structuralisomersof each are other,and arecommonlyknownbytheir nonsystematic names. prefix r- (normal) The refersto a straight-chain alkyl group,the point of attachment beingat an end C atom. The isomerof the n-propyl group is the isopropylgroup.Figure5 showsthe common namesfor isomersof the butyl group;in this book,we will not concernourselves with isomersof alkyl groupsgreater than 4 C atoms. (a) CHrCHr- CHr- CHr(b) CH,CH CH3

(a)

cH,- cHr- cHr(normal propyl) n-propyl (b)

cHr- cH- cH3

Iisopropyl Figure 4 of Twoisomers the propylgroup. bondindicates where Thecoloured the groupis attached the larger to molecule.

I(normal n-butyl butyl)isobutyl (c) CH,CH CH2CH3 (d) CH,

CH,

I

Is-butyl(secondary butyl) Figure 5 of Fourisomers the butylgroup

cH.- c - cH3

II

with isomera compound the same as commolecular formula another pound, a different molecular but structure

f-butyl(tertiary butylJ

l.

Write the IUPAC name for the chemical with the following structunl diagram.

CH,

CH,

CH,

I

ICH,

cHr- cHr- cH - c H - c H - c H 3

t

CH,

t

First, identify longest the carbonchain.Notethat you mayhaveto countalongwhat appeartobe branches the structural in diagram makesureyou truly havethe longest to chain.In this case, longest the carbon chainis 6 C long.So the parentalkaneis hexane. Next,numberthe atomsas shown. C

u9t' 9n,

,9t, 9t, 9il,cHr- cHr- cH - cH - cH - cH36 5 4 3 2 L a

possible In this case, thereareseveral six-carbon the chains. Choose onethat givesthe lowestpossible totalof numbers the identifying location the branches. of Usually is best it to startnumbering with the end carbon that is closest a branch. this case, first to In the branchis on C 2. Notice that it makes difference no C whetherwechoose la orC 1b to be the actualC l.

Compounds13 Organic

Nameeachbranch andidentify location the parent its on chain. thisexample, In there groupon C 2 andan ethylgroupon eachof C 3 andC 4.Thusthe branches is a methyl are2-methyl, 3-ethyl, and 4-ethyl. got the To checkthat you've the lowest total,try naming structure fromthe otherends of the chain.lf we had counted from eitherofthe C 6 ends, wouldarriveat 3-ethyl, we and 4-ethyl, S-methyl-a of numbers set with a highertotal. Whenthe samealkylgroup(e.9., ethyl)appears morethanonce, theyaregrouped as di-, tri-, tetra-,etc.In this compound, two ethylgroups combined 3,4-diethyl. the are as (number writethe complete Finally, IUPAC name, following format: this locaindicating tionJ-(branch nameJ(parent chain). thisbook, In whenmorethanonebranch present, is (Notethat othersources the branches listedin alphabetical are order. maylistthe branches orderof complexity.) in ethyl Alphabetically, comesbeforemethyl. the name So begins followed the methylgroup,and endswith the parent with the ethylgroups, by alkane. Watch useof commas hyphens, notethatno punctuation used the and and is the between alkanenameand the alkylgroupthat precedes it. TheIUPAC name forthiscompound 3,4-diethyl-2-methylhexane. is 2. Write the IUPAC name forthe following hydrocarbon. cHrcH2I

cH3

cHr-

cHr- cH -

cHr.- cH, - cH, - cH2- cH3

First, the So identify longest carbon chain:8 C atoms. the molecule an octane. is Next, the as number C atoms shown. CH"la " CH,l'; CH"

cH3 -2cH2 -ra"

-

-scH 2 6cH2 lrr4cH2

ran'

at to so lf we startcounting C I, the branchgroupattached C 3 contains C atoms, it is 3 a propylgroup.However, propylgroupis attached the parentchainat its middleC the to atom,not at an end C atom. Thisarrangement the propylgroupis calledisopropyl of (Figurea(b)). Onepossible name forthiscompound 3-isopropyloctane. is a this However, different nameresults we number hydrocarbon if fromthe top branch.

cHr-cH-cH3

1

2

I cH, cH, cH- 9H,- 9H, 9H, 9H, gH,groupon C2and an ethylgroupon C 3, giving name Thisshows methyl a the 3-ethyl-2-methyloctane. morethanone nameis correct, usethe onethat Where we possible includes lowest the numerals. Thecorrectnameof this compound 3-ethyl-2-methyloctane. is

CH.

IrCH , / \ ,CH, ,CH, \ / ocHr-3cH-cH3

3.

Draw a structural diagram for 1,3-dimethylcyclopentane.

The parentalkaneis cyclopentane. by drawinga ringof 5 C atomssingle-bonded Start to in eachother, the shapeof a pentagon. Next, C anywhere the ring. numberthe atoms the ring,starting in in Thenattacha methylgroupto C 1 and anothertoC 3. Finally, H atoms the C atoms complete bonding the diagram. add to to the and

14

ChapterI

Section1.2

ExampleWrite IUPAC the name forthe following hydrocarbon. CH,

cHr-cHr-cH-c-cH-cHcH3 cH2

I

CH, SolutionThisalkaneis 3,4,4-trimethylheptane.

I

Naming Branched AlkanesStepI Identiff the longestcarbonchain;note that structuraldiagrams be can deceiving-the longestchainmay travelthrough one or more "branches" the diagram. inof moleThestructure an organic in culecan be represented many ways: somerepresentadifferent detail; tionsgivethree-dimensional to others simplified showonly are backbone funcand the carbon The structionalgroups. following all turaldiagrams showthe same acid-butin molecule-pentanoic different ways. slightlyU-au -a-nH -eE vr r) vr rl

Step2 Number the carbonatoms,startingwith the end that is closest the to branch(es). Step3 Nameeachbranchand identifr its locationon the parentchainby the number of the carbonat the point of attachment. Note that the name (This may with the lowestnumeralsfor the branches preferred. is requirerestarting your count from the other end of the longestchain.) Step4 Write the complete IUPACname,following this format: (numberof location)-(branch name)(parent chain). Step5 When more than onebranchis present, branches listedeitherin the are alphabetical order or in order of complexity;in this book,we will follow the alphabetical order. Note \',Vhen naming ryclic hydrocarbons, carbonatomsthat form the ring the structureform the parentchain;the prefixcyclo-is addedto the parent hydrocarbon name,and the namingof substituted groupsis the sameas for non-ryclic compounds.

Understanding Goncepts 1. WriteIUPAC names forthe following hydrocarbons. [a] CH, CH, CH,

lcHr-cH

- cH - cH - cH - cH2- cH3

l

t

l

CH,

CH,

4-ethyl-2,3,5-trimethyl heptane

O r g a n iC o m p o u n d s 5 c 1

15) CH:-

cH cH2-

CH, - CH, cH3

CH,-

CH -

CH3cH3

lcH2(cl CH2CHI

cH,- cH- cH,- cH- cH,- cH- cH3 l lcH, (dl gH,I CH CH,, ' " t /

I

cH2cH2cH3

,CH, CH

ICH, \ / / CH,

ICH,

2. Drawa structural diagram foreachof the following hydrocarbons: (aJ 3,3,S-trimethyloctane (bJ 3,4-dimethyl-4-ethylheptane (cJ 2-methyl-4-isopropylnonane (dJ cyclobutane (eJ I,l-diethylcyclohexane

Alkenesand AlkynesThe general rulesfor namingalkenes alkynes similar to thosefor alkanes, and are using the alkyl prefixes and endingwith -eneor -ynerespectively.

l,

Write the IUPAC name forthe hydrocarbon whose structunl diagnm and ball-and-stick model are shown. CH,CH CH: CH,

ICH, First, find the longest chainthat includes multiple C the bond.In this case, is 4 C long, it so the alkene a butene. is Numberthe atoms, C beginning the endclosest the double with to bond. Thedoublebondis between 1 and C 2. so the alkene a l-butene. C is CH,4 ' CH ' l CH : 2 CH" 1

F",Next,identify branches: methylgroupis attached C 3, so the branchis any A to 3-methyl. Finally, writethe name, following conventions hyphenation punctuation. the for and precedes word butene, Sincea number the are hyphens inserted the alkeneis and 3-methyl-1-butene.

16 Chapter I

Section1.2

2,

Draw a structural diagram for 2-methyl-1,3-pentadiene.

First, drawand numbera C chain 5 forthepentadiene. C-C-C-C-Ct 2 3 4 5

"diene" Nowinsert double the bonds. name The tellsus thattherearetwo double bonds, one starting C 1 and another at starting C 3. at C:C-C-C-Ct 2 3 4 5

Drawa methylgroupattached C atom2. to CH,

IC:C-C-C-C1 2 3 4 5

Finally, writein the remaining atoms. H CH,

ICHz:C-CH:CH-CH, 3. Write the IUPAC name forthe compound whose structural diagnm and balland-stick model are shown.

n$ ." ,First, identify ring structure, the whichcontains C atoms 6 with one doublebond. The parentalkene therefore is cyclohexene. I Next, numberthe atoms C beginning with oneof the C atoms the double in bond. numbering The system should t-Y^.", grouphaving resultin the attached the lowestpossible number, whichplaces groupat C 3 . the methyl TheIUPAC name forthiscompound 3-methylcyclohexene. is

,O]

Example I-butyne. Drawa structural ramfor 3,3-d diag imethyl-l

Solution CH,

ICH:C-C-CH,

ICH,

Compounds17 Organic

Example 2Writethe IUPAC name forthefollowing compound. CHr:CH-C:CHCH2-CH3

cHr- cH - cH3 SolutionThecompound 3-isopropyl-1,3-hexadiene. is

I

Some alkenes and alkynes have common names. Step l.

Naming Alkenes and AlkyrnesThe parent chain must be an alkene or alkyne, and thus must contain the multiple bond. Step 2. lvVhennumbering the C atoms in the parent chain, begin with the end closestto the multiple bond. Step 3. The location of the multiple bond is indicated by the number of the C atom that begins the multiple bond; for example,if a double bond is betweenthe secondand third C atoms of a pentene,it is named 2-pentene. Step 4. The presence and location of multiple double bonds or triple bonds is indicated by the prefixesdi-, tri-, etc.;for example,an octenewith double bonds at the second,fourth, and sixth C atoms is named 2,4,6-octatriene.

UnderstandingGoncepts 3. Explain no number usedin the names why is ethene propene. and 4. Writethe IUPAC name andthe common name forthecompound Figure6. in

Figure 6 Whenthis compound combusts, transfers it enough heatto meltmostmetals. 5. WriteIUPAC names forthe compounds the following with structural diagrams: (a) CH, CH,

cHr-c:c-cH-cH-cH,cH2 -

I

cH3

'l 18 Chapter

Section1.2

(bl CH,- CH:

CH.-

cHr-

cH,

C - cH2- cH3 (cl CH3CH: CH - CHr- CH: CH (d) C H r : C H - C H : C H - C H - C H 3I

I

CHr-CH:

CH,

cHr(e)

cHz- cH2

CH,.1

Y

)CH,

6. Drawstructural diagrams eachof the following for compounds: (aJ 2-methyl-5-ethyl-2-heptene (bJ 1,3,5-hexatriene (cJ 3,4-dimethylcyclohexene (d) l-butyne (e) 4-methyl-2-pentyne

AromaticHydrocarbonsIn namingsimplearomaticcompounds, usuallyconsider benzene we ring to be the the parentmolecule, with alkyl groupsnamedasbranches attached the benzene. to For example, a methyl group is attached a benzene if to ring, the moleculeis called (Figure7). Since 6 C atomsof benzene in a ring, with no beginmethylbenzene the are ning or end,we do not needto includea number when naming aromaticcompounds that containonly one additionalgroup. Whentwo or moregroupsareattached thebenzene to ring,we do needto usea numberingsystem indicatethe locations the groups. always to of We numberthe C atomsso that we havethe lowestpossible numbersfor the points of attachment. Numberingmay proceedeither clockwise counterclockwise. shownin the examples Figure 8, or As in we startnumberingwith oneof the attached ethylgroups, then proceed the direction in that is closest the next ethyl group. to C,H, C,H, C,H, lr CH,

..A,

Figure 7 Methylbenzene, commonly called is liquid that is toluene, a colourless butwilldissolve insoluble water, in in fluids. is alcohol otherorganic and lt in usedas a solvent glues andlacquers andis toxicto humans. Toluene reacts with nitricacidto produce the trinitrotoluene explosive [INT).

t ( ) 'vr, lel crHtFigure 8 of Threeisomers diethylbenzene

C,H,4

(a) 1,2-diethylbenzene

(b) 1,3-diethylbenzene

(c) '1,4-diethylbenzene

Organic Compoundsl9

Youmayencounter speciala izednaming system-known as the classical system-for benzeneringswith two substituted groups. Forthe threeisomers of diethylbenzene shownin Figure 8 , t h e 1 , 2 -1 , 3 -a n d1 , 4 , , arrangements denoted are by the prefixes ortho-(o),meta[m], and para-[p), respectively. Thus,o-diethylbenzene refers to 1,2-d iethylbenzene, m-diethylbenzene refers 1,3-diethylto benzene, p-diethylbenzene and refers 1,4-d to iethylbenzene. These names stillusedin are industry, you may and encounter themin other references. doubtyouagree No that the replacement these of letter names withthe IUPAC numbering system a welcome is simolification.

Building HydrocarhonsMaterials: molecular modelkits. . Froma molecularmodel obtain6 carbons kit. and 14hydrogens. (a) Build, draq and nameas manyhydrocarbonsas you can,usingall 20 pieces each in model. (b) Putaway2 hydrogen atoms, and buildand nameas manydifferentstructures posas sible, usingall of the remaining atoms. (c) Repeat as manytimesas possible, (bJ until you can no longerconstruct hydroany carbonmolecules. (d) Whichof the compounds isomers? are

For some aromatic moleculeswhere the attached group is not easilynamed,it is more convenientto considerthe benzenering as a branch rather than as the parent molecule.When the benzenering is the attached branch, -CoHs, it is called a phenyl group. For example, the compound shown in Figure 9 is named 2-phenylbutane.According to the naming systemfor branched alkanes(seepage 13), it may also be calleds-butylbenzene. Either naming systemfor aromatic compounds is acceptable; object is to choosethe more conthe venient method for the compound in question.

cHr-cH-cH2-cH3

Figure 9 2-phenylbutane, or s-butylbenzene

Draw the structural diagram for S-ethyl-l -methylbenzene. CH, First, drawthe benzene thenadda ring, groupto anyC atomof the ring;this methyl C atomautomatically becomes 1 in the C numbering system. Finally, an ethyl add groupto C 3, whichcan be clockwise or counterclockwise C l. from ,l u /,=-\ , | ( ) | . I " L \.-/ CH2CH3 \-,/r-

ExampleWrite IUPAC names forthe following aromatic hydrocarbons.(a)

cHr- CH,

(b) CH, : CH -

I

cH2cH2cH3CHr CH CH2 CH3

r,Al-

CH,

\ZCH,20 Chapter I

Section1.2

Solution(a) 1-elhylZ,4-di methylbenzene (bJ 4-phenyl-3-propyl-l-hexene

Nami ng Aromatic Hydrocarbonsl. If an alkyl group is attached a benzene to ring, the compoundis namedasan allcylbenzene. Alternatively, benzene the ring may be considered a branch as of a largemolecule; this case, benzene in the ring is calleda phenylgroup. 2. If more than one alkyl group is attached a benzene to ring, the groupsare numberedusingthe lowestnumberspossible, startingwith one of the added groups.

7. WriteIUPAC names forthe following hydrocarbons. (a) CHI-CH,-CH_CH-CH3

'.Al t

c'H') l

vIC,H,

(b) CH2-CH:CH-CH

ICH,

(c) CH-C-CH,-CH-CH3

(dl

CH,

r,A

I

Y

CH2CH,CH..

Drawstructural diagrams forthe following hydrocarbons: (aJ 1,2,4-trimethylbenzene (b) 1-ethyl-2-methylbenzene (c) 3-phenylpentane (d) o-diethylbenzene (eJ p-ethylmethylbenzene

Organic Compounds21

PhysicalPropertiesof HydrocarbonsSince hydrocarbons contain only C and H atoms, two elements with very similar electronegativities, bonds between C and H are relatively nonpolar. The main intermolecular interaction in hydrocarbons is van der Waals forces: the attraction of the electrons of one molecule for the nuclei of another molecule. Sincetheseintermolecular forcesare weak,the moleculesare readily separated. The low boiling points and melting points of the smaller molecules are due to the fact that small molecules have fewer electrons and weaker van der Waals forces,compared with large molecules (Table 3). These differencesin boiling points of the components of petroleum enablethe separationof these compounds in a processcalled fractional distillation. Hydrocarbons, being largely nonpolar, generally have very low solubility in polar solvents such as water, which is why gasolineremains separatefrom water (Figure l0). This property of hydrocarbons makes them good solventsfor other nonpolar molecules. Table 3 Boiling Points the First10Straight of Alkanes

Figure lo hydrocarbonsgasoin Thenonpolar in and lineareinsoluble water phase. in remain a separate

fractional distillation the separation of by of components petroleum distilusingdifferences boiling in lation, points; called also fractionation

Understanding Goncepts diagram eachhydrocarbon: 1. Drawa structural for (a) 2-ethyloctane (bl 2-ethyl-3-bepropylnonane (cJ methylcyclopentane (d) 3-hexyne (e) 3-methyl-1,5-heptadiene t0 1,2,4-trimethylbenzene (gJ 4-s-butyloctane (hJ 2-phenylpropane 0l 3-methyl-2-pentene (l n-propylbenzene [k) p-diethylbenzene 0) 1,3-dimethylcyclohexane

2. Foreach the following of names, determine it is a correct if namefor an organic compound. Givereasons your for answer, including correct a name. (aJ 2-dimethylhexane [bJ 3-methyl-l-pentyne [c) 2,4-dimethylheptene [d) 3,3-ethylpentane (eJ 3,4-dimethylhexane (fJ 3,3-dimethylcyclohexene (g) 2-ethyl-2-methylpropane (h) 2,2-dimethyl-l-butene (D 1-methyl-2-ethylpentane 0l 2-methylbenzene (kJ 1,5-dimethylbenzene 0l 3,3-dimethylbutane

22

I Chapter

Section1.2

Write correct IUPAC names forthe following structures. (aJCH,CH,CH: CHCHCH: CHCH3 cH3cHCH3 (b] CH,CH"

(e) CH"CHCH,

ICH3CCH:CH,

IcH2cHCH2CH3 4. Drawa structural diagram foreachof the following compounds, writethe IUPAC and name foreach: [a) ethylene (b) propylene (c) acetylene (dJ toluene, toxicsolvent the usedin manyglues (e) the o-, m-, andp- isomers xylene(dimethylbenof zene), usedin the synthesis otherorganic of compounds suchas dyes Making Connections 5. (a) Usethe information Table3 to plota graphshowing in the relationship between number carbonatoms the of points the alkanes. andthe boiling of Describe and propose explanation an you fortherelationship discover. (b) Research useforeachofthe first 10alkanes, a and suggest why eachis appropriate this use. for

CH, (cl CH,

IcH3cH2cHCHCH3

r,A\2(d)

cH2cH3

I

alcH2cH3

L_l

Go|

www.science.nelson.com

Organic Compounds 23

All hydrocarbonsreadily burn in air to give carbon dioxide and water,with the release for of largeamountsof energy(Figure l); this chemicalreactionaccounts the extenIn siveuseof hydrocarbons fuel for our homes, as cars,andjet engines. other chemical reactions, are and alkynes, result of the a alkanes generally lessreactivethan alkenes presence more reactive doubleand triple bondsin the latter.Aromatic compounds, of with their benzene rings,aregenerally more reactive than the alkanes, lessreactive and and we than the alkenes alkynes. this section, will examine trend in the chemical In this reactivity of hydrocarbons.lll When we arerepresenting reactionsinvolving largemolecules, is often simplerto use it a form of shorthandto represent variousfunctionalgroups.TableI showssomeof the the commonly usedsymbols.For example,R-A represents alkyl group attached any to a benzene ring, and R-X represents alkyl group attached anyhalogenatom. any to TableI Groupalkylgroup Figure 1 Hydrocarbons foundas solids, are liquids, gases, of whichburn and all to oroduce carbondioxide and water, and largeamounts light of and heatenergy. halogen atom phenyl group

of Functional Groups ExamplesSymbols RepresentingSymbol primeJ R, R', R', etc.(R,R-prime, R-double

Reactions Alkanes ofThecharacteristic reactions andunsaturated hydrocarbons be explained can ofsaturated hydrocarbons. by the typesof carbon-carbon bonds in saturated and unsaturated Singlecovalent bondsbetween carbonatomsare relativelydifficult to break,and thus alkanes ratherunreactive. are They do undergocombustionreactionsif ignited in air, makingthem usefirlfuels.Indeed, hydrocarbons capable combustionto proare all of ducecarbondioxideandwater. The reactionof propanegas, commonlyusedin gasbarbecues, shownbelow: is -+ caHs@l 5or6n1 3co2@) 4H2o@l + + While the C-C bondsin alkanes difficult to break,the hydrogenatomsmaybesubare stitutedbyahalogen atom in a substitutionreactionwith F2,Cl2,or Br2.Reactions with F, arevigorous,but Cl2 and Br, requireheat or ultraviolet light to first dissociate the halogenmolecules beforethe reactionwill proceed. eachcase, product formed is In the a halogenated alkane;asthe halogenatom(s) act as a functional group, halogenated alkanes alsoreferredto asan organicfamily calledalkyl halides. are In the reactionof ethane with bromine,the orangecolour of the bromineslowlydisappears, the presence HBrlryis indicated a colourchange moistlitmus paper and of by of from blueto red.A balanced equationfor the reactionis shownbelow. H HHg) * Brr,1, -----+ H-

Preparation of Ethyne yield Howclosedoesthe actual yieldin the cometo the theoretical reaction between calcium carbide andwater?

combustion reaction the reaction proof a substance with oxygen, ducingoxides and energy substitution reaction a reactionin which a hydrogen atomis replaced by another atomor groupof atoms; reaction alkanes aromatics of or with halogens produce to organic halides hydrogen and halides alkyl halide an alkanein whichone ormoreofthe hydrogen atomshave beenreplaced with a halogen atom as a resultof a substitution reaction

H B rCI H

t

H-C-C

CI H

l

lH H

l

heatorWlight

H,1, + HBr,1, (substitution reaction)

bromoethane. (ethylbromide) 24 Chapter 1

Section1.3

As the reactionproceeds, concentration bromoethane the of increases bromine and reacts with it again, leading the substitution anotherof its hydrogen to of atoms, forming 1.2-dibromoethane.H

I I

Br

I

Br

Br

H-CH

? ,l

-"*, +Br2,*, + H- 9 - 9 -Hu, *HBr,*, (substitution heat W light | or ,l reactionJr.2-dibromoethane

Additionalbromines maybeadded, resulting a mixtureof brominated in products that (because differences physical of properties) be separated procedures asdisin can by such tillation.

Reactionsof Alkenes and AlkynesAlkenes alklmes and exhibitmuch greater chemical reactivitythanalkanes. example, For the reactionof theseunsaturated hydrocarbons with bromine is fast,and will occur at (Figure2). (Recall room temperature that the bromination of alkanes requires heator W light.) This increased reactivityis attributedto the presence the doubleand triple of bonds.This characteristic reactionof alkenes and alkynesis calledan addition reaction asatomsareaddedtothe moleculewith ro los of hydrogen atoml Alkenes and a$mes canundergoadditionreactions onlywith halogens, also not but with hydrogen, hydrogen halides, water, and giventhe appropriate conditions. Examples of thesereactions shownbelow are

Figure 2 The reaction cyclohexene of and bromine water,Brr1"o1,rapid, is forminga layerofbrominated (clearJ. cyclohexane addition reaction a reactionof and alkenes alkynes whicha in molecule, suchas hydrogen a or halogen, added a double is to or triplebond

Halogenation(with Br, or Cl2)Br HBr C : C -H*Br,,*, + (addition H- C - C -H reaction) l l r o o m l l H H t e m p e r a t u r e H H ethene l,2-dibromoethaneTable 2 Prefixes Functional for Groups

(with H2) HydrogenationH-C:C-H+ catalyst 2H,t*t HH H I I C - C -H pressure I heat, I H H ethane (addition reactionJ

ethyne

(with hydrogenhalides) HydrohalogenationH H-C:CH-CH,+HBr,*; Hroom temperature C CHI H 2-bromopropane

I-

B

rCH, fadditionreaction)

I

H propene

Margarine Vegetable consist molecules of oils with long hydrocarbon chainscontaining many double bonds; these "polyunsaturated." oilsare called Theoilsare"hardened" underby goinghydrogenation reactions to produce moresaturated molecules, similarto thosein animal fatssuchas lard.

Organic Compounds25

Hydration(with HzO)H2SO4 H OH catalyst | | reactionJ CHCH, + I{OH ------_HzC - CH- CH, [addition (an alcohol) propene 2-hydroxypropane

H-CH:

Markovnikov'sRuleWhen molecules suchasH2,consisting two identical of atoms,areaddedto a double product is formed;in other words,addition of identicalatoms bond, only onepossible products. to eithersideof the doublebond results identical in When molecdesof nonidentical however, dffirent productsare atomsareadded, two theoreticallypossible. example, For whenHBr is added propene, H mayaddto C to the products possible, shownbelow atom 1,or it mayaddto C 2; two different are as + HBrH-CH: HrC - CH- CH3 or H,C - CH- CH3 CH- CH. H B r B r H propene 2-bromopropane 1-bromopropane product) [main Experiments showthat, in fact,only onemain productis formed.The productcanbe predictedby a rule known asMarkovnikov'srule, first statedby Russian chemistV. V. ( 1838-1904). MarkovnikovMarkovnikov's Rule Whena hydrogen halide orwateris added an alkene to or alkyne, hydrogen the atombondsto the carbonatomwithin the doublebondthat alreadyhasmorehydrogen afoms. This rulemaybe remembered simplyas "the rich get richer." As illustrated in the reaction of propene above, the first C atom has two attached H atoms, while the second C atom has only one attached H atom. Therefore, the "rich" Cl atom "gets richer" by gaining the additional H atom; the Br atom attachesto the middle C atom. The main product formed in this reaction is 2-bromopropane.

t

l

What compound will he produced when water reacb with 2-methyl-l-pentene? -pentene. First, writethe structu form la for 2-methyl-1 ral u CH3CH'CH'C: 5 4 r 2 l CH, Next,identify C atomwithinthe doublebondthat hasmoreH atomsattached. the Sincecarbont hastwo H atomsattached, carbon2 hasno H atomsattached, the and H atomin the HOHaddsto carbon andthe OHgroupaddsto carbon l, 2. We can now predict productof the reaction. the O H H CH3CH2CH2C: s 4 t r l CH, CH, + HOH 1 CHTCHTCHTC s 4 3 2 1 CH, CH, , CH' r

pou Thecom nd prod ucedis 2-hydroxy-2-methylpentane.

26 Chapter I

Section1.3

ExampleDrawstructural diagrams represent addition to an reaction an alkene produce of to 2-chlorobutane.

Solution

T C IHrC : CHCH2CH3 HCI -+ HrC - CHCH2CH3 + 1-butene

Understanding Goncepts 1. Whatcompounds be produced the following will in addition reactions?

(al

cHrcH-ccH2cH3H, + l H#I

cH2cH3 (bl CH:CH-CCH2CH3 * HBr----) CH, tcl Lur cH3cH2cHCH:cHz I cH2cH3 + H2o H.sc .'zru+ ,

(d) rl

-> (-,Jl * ct'

Synthesis: Ghoosing Whereto StartAddition reactions important reactions are that areoften usedin the synthesis comof plex organicmolecules. Carefulselection an alkeneasstartingmaterialallowsus to of strategically placefunctional groupssuchasa halogenor a hydroxylgroup ( -oH) in positionson a carbonchain.As we will see desired later in this chapter, productsof the theseaddition reactionscan in turn takepart in further reactions synthesize to other organiccompounds, suchasvinegars and fragrances.

Understanding Concepts 2. Explain phrase the "the rich get richer"as it applies Markovnikov,s to rule. 3. Drawstructural diagrams represent to addition reactions produceeachof the to following compounds: (aJ 2,3-dichlorohexane (b) 2-bromobutane roxy-3-methylpentane [cJ 2-hyd (d) 3-hydroxy-3-methylpentane

Organic Compounds27

Reactionsof Aromatic HydrocarbonsSince aromatic hydrocarbons are unsaturated, one might expect that they would readily undergo addition reactions, as alkenes do. Experiments show, however, that the benzenering does not undergo addition reactions exceptunder extreme conditions of temperature and pressure.They are less reactive than alkenes. Aromatic hydrocarbons do undergo substitution reactions, however, as alkanes do. In fact, the hydrogen atoms in the benzene ring are more easily replaced than those in alkanes.When benzene is reacted with bromine in the presenceof a catalyst, bromobenzeneis produced. Overall, the reactivity of aromatic hydrocarbons appearsto be intermediate between that ofalkanes and alkenes. (a) cyclohexane * Br, -+ bromocyclohexane

* HBr I l* Br2 -----------) | | l l h e a t W l l \-'\-'cyclohexane bromocyclohexane (b) benzene + Br, -+ bromobenzene

'^"Yu'

(substitution reaction)

/

\

z.A-.-.

er

l( )l*un-lt%l( )l

vI

benzene

v

*HBr:',H:H::J",.X:'""

bromobenzene

(c) cyclohexene+ Br2 -> bromocyclohexane Br

a\\-,

,/ --^\ t l * B r , -------------)lroom | temperature \

Iv.r.

Br (additionreaction)

l ||

cyclohexene

\.,/ 1,2-dibromocyclohexane

Further reaction of bromobenzenewith Br, resultsin the substitution of another Br on the ring. In theory, this second Br atom may substitute for an H atom on any of the other C atoms,resulting in three possibleisomersof dibromobenzene.

Br

Br

.A a -Y'Bt l( )l+Br:_+l)l (

v

v

rA

Br I

Br

v

'-A l t ( )Br Br 1,4-dibromobenzene

I

Y

l, 2-dibromobenzene

1,3-dibromobenzene In practice,the 1,3 isomer appearsto be favoured.

2A Chapter 1

Section1.3

The relativelylow reactivity of aromatichydrocarbonsindicatesthat the benzene structureis particularlystable. seems It that the bondsin a benzene ring areunlike the doubleor triple bondsin alkenes alkynes.In1865, Germanarchitect or the and chemist Friedrich AugustKekuld(1829-1896) proposed cyclicstructurefor benzene, a CuH6. With 6 C atomsin the ring, and oneH atom on eachC atom,it appears theremight that bondswithin the ring,each be 3 double alternating with a single bond.As carbon-carbon doublebondsareshorterthan singlebonds,we would predictthat the bondsin the benzene would be of differentlengths. ring Experimental evidence, however, othshows The technique X-ray diffraction indicates erwise. of that all the C-C bondsin benzene areidenticalin lengthand in strength(intermediate between that of singleand double bonds).Therefore, ratherthan having3 doublebondsand 3 singlebonds,an acceptablemodelfor benzene would requirethat thevalence equally electrons shared be among making6 identical all 6 C atoms, A bonds. modelof benzene shownin Figure3. In this is model,the 18valence electrons shared are equally, a delocalized in arrangement; thereis no specificlocation for the sharedelectrons, and all bond strengths intermediate are that between of single doublebonds. and Thisexplains benzene why ringsdo not undergo additionreactions doublebondsdo, andwhy theydo undergosubstitutionreactions as assingle bondsdo,and do somorereadily. Chapter you will examine moredetail In 4, in the uniquebonding that is present the benzene in ring. In anothersubstitutionreaction,benzene reacts with nitric acid in the presence of H2SO4 form nitrobenzene. to Benzene reacts also with alkyl halides(R-X) in the presenceof an aluminum halide catalyst(AlXt); the alkyl group attaches the benzene to ring, displacing H atom on the ring. These an productscanundergofurther reactions, enabling design the and synthesis aromaticcompounds of groupsattached with desired positions. in specific

',\ |!!

H2so4,l\-No'z + HNO3--------) |!!nitrobenzene Alcl3

+ H2O (substitution reaction)

Figure 3 wrotethe following diary Keku16 entryabouta dream had,in he whichhe gained clueto the struca 'Again ture of benzene: the atoms gambolled beforemy eyes. Thistime groupskeptmodestly to the smaller eyes, the background. mind's My moreacuteby repeated rendered visions a similar of kind,couldnow distinguish larger structures, varof iousshapes; longrows,sometimes moreclosely fittedtogether; all twining andtwisting snakelike in motion. looklWhatwasthat? But grabbed own Oneof the snakes its mockingly tail,andtheformwhirled beforemy eyes. if struckby lightAs ning I awoke; I spentthe restof ... the nightin working the conseout quences the hypothesis.... of lf we learnto dreamwe shallperhaps the discover truth."

cH2cH3+ HCI reaction) [substitution

+ cH3cH2cl ---------)ethylbenzene

Predict the product or products tormed when benzene is reacted with 2-chlorohutane, in the presence of a catalyst (AICI). Dnw structural diagrams of the reactants and products. groupofchloromethane Themethyl substitutes foroneofthe H atoms the benzene on ring, forming methylbenzene releasing chloride reactwiththe displaced and the to hydrogen.

.; l(

(\-/,-\-,'-

)l+cl-c-H---+l(

t

,r,H

,lYcH3 )l

\2

+HCl

(toluene) hydrogen Theproducts formedare methylbenzene and chloride.

NEL

Organic Compounds29

ExampleDrawbalanced chemical equations diagrams) represent series to a Includingstructural of reactions wouldtakeplaceto synthesize that ethylbenzene benzene ethene. from and Classify eachreaction.

Solution(by Reaction Halogenation addition) ethene hydrogen t: of by chloride H C IH-C:C-H+HCI +

I

H-C-C-H

H ethene

H

H

H chloroethane

I

(by Reaction2: Halogenation substitutionJ benzene chloroethane of by

. , irr),) l +, H - C | C-- H \ | ( -

T*H

C

\ Vy t t H

I I //-+) FHC -ICH H + H C I ( ( -

\ H- / tH l

Understanding Goncepts +. Predict productor products the formedin eachof the following reactions:

G) .A\l(

(bl

\2

) l + c l ,- )

41-rNo'l(

v

)l

+HNo3#

H,so,

5. Propose reaction a series that wouldproduce 2-phenylbutane, starting with benzeneand l-buteneas reactants. "substitution," "halogenation" 6. Whichof the terms"addition," or describes reacthe tion between benzene bromine? and Explain. 7. Describe bonding the structure benzene, explain experimental in and the evidence in supportof this structure.

Reactionsof Hydrocarhons' All hydrocarbons undergocombustionreactions with oxygento producecarbon dioxideand water.

Alkanes. Primarily undergosubstitution reactions, with heator W light: with halogens hydrogen or halides: halogenation with nitric acid

30 Chapter I

Section1.3

Alkenes and Alkynes. Primarilyundergo addition reactions: with H2:hydrogenation with halogens hydrogen halides: halogenation or with water:hydration

Aromatics. Primarilyundergo substitutionreactions: with Xr: halogenation, O-X with HNOr: nitration,O-NO2 with RX: alkylation, O-R . Do not undergo additionreactions.

UnderstandingGoncepts 1. Writea balanced equation foreach thefollowing of types of reactions acetylene: of (cJ halogenation [aJ addition (b) hydrogenation (dJ hydration 2. Classify eachof the following reactions one of the folas lowing types: addition, substitution, hydrogenation, halogenation, combustion. the names the or Write and structures forall reactants products. and -> (a) methyl-2-butene hydrogen * (b) ethyne+ Cl2-) --) (cl CH:-C-C-CHI * H2 (excessJ (d) CrHt

Applying Inquiry Skills products, select reacthe 4. To makeeachof the following conditions needed. tantsanddescribe experimental the (a) 2-hydroxypropane (b) 1,3-dichlorocyclohexane cyclohexane from (c) 2-melhyl-2-hydroxypentane an alkene from (d) chlorobenzene Making Connections gas werecompletely lf a certain volumeof propane at SATP of combusted oxygen, in wouldthevolume gaseous product thanthatof the formed greater smaller or be reactant? how much? By attractions, Fromyourknowledge intermolecular of which of these organic compounds-2-chlorononane, 2-hydroxynonane, nonane-would the mosteffective be solvent or Givereasons for removing stains? oil foryouranswer. TNTis an exolosive a colourful with and history figure 5J.Research it, reporton who discovered and its uses, and development, synthesis, misuses. Figure 5

* cHr-Q11, [e] CrH,CH3-CH-C-CH-CH3

>

I

ICH,

* O-O

------z

3. Classify writestructural and formula equations the folfor lowing organic reactions: (aJ 3-hexene waterH2so4 + -+ (bl 2-butene hydrogen butane + -) + hydrogen [c] 4,4-dimethyl-2-pentyne 2,2-dimethylpentane --r (dl methylbenzeneoxygen carbon + t dioxide water -+ [e) 2-butene 3-methylpentane

R

www.sctence.ne lson.com

Organic Compounds31

organic halide a compound of carbon andhydrogen whichone in ormorehydrogen havebeen atoms replaced halogen by atoms

Organichalidesarea group of compounds that includes manycommonproductssuch asFreons(chlorofluorocarbons, CFCs)usedin refrigerators and air conditioners, and Teflon(polytetrafluoroethene), nonstickcoatingusedin cookware the and labware. While we usesomeorganichalides our everyday in lives,manyothersaretoxic and some arealsocarcinogenic, their benefitsmust be balanced so potentialhazards. against TWo suchcompounds, insecticide the DDT (dichlorodiphenyltrichloroethane) the PCBs and (polychlorinated biphenyls)usedin electrical transformers, havebeenbannedbecause of public concernabouttoxicity. In Section1.3you learnedthat when H atomsin an alkaneare replaced halogen by atoms,the resultingorganichalideis more specifically referredto asan alkyl halide.

NamingOrganicHalidesWhennamingorganic halides, consider halogen the atomasan attachment theparent on hydrocarbon. halogen The nameis shortened fluoro-, chloro-,bromo-, or iodo-. For to example, structureshownbelowis 1,2-dichloroethane, the indicatingan ethanemolecule substituted with a chlorineatom on carbon I and a chlorineatom on carbon2.

cl

ct

H-C-C-H H H I ,2-dichloroethane

Dnw a structunl diagnm for 2,2,54rtbromo-5-methylhexane. parentalkane First, drawand numberthe chain, hexane: the C-C -C -C -C -C1 2 3 4 5 6

groupto Next, addWvo Bratoms carbon one Bratomto carbon and a methyl to 2, 5, Br

C-C-C-C-C-C1 2 3 4

tI

Br

l6

5

Br carbon 5.

CH.

Br

cH3ccHrcH2ccH31 2 3

t

Br4

l

Br

t

5 6

CH,

l

32 Chaoter 1

Section1.4

Finally, complete bonding adding atoms the C atoms. the by to H

Example IWritethe IUPAC namefor CH.CHTCH2CH(CDCH2CH(BrJCH..

SolutionThiscompound 2-bromo-4-chloroheptane. is

Example 2Drawa structural diagram 1,2-dichlorobenzene. of

Solution

CI

frtctt t()

I

v

UnderstandingConcepts l. Drawstructural diagrams foreachof the following alkylhalides: (a) 1,2-dichloroethane (solvent rubber) for (bJ tetrafluoroethene (usedin the manufacture ofTeflonJ (c) 1,2-dichloro-1,1,2,2-tetrafl (refrigera uoroethane ntJ (dJ 1,a-dichlorobenzene repellent) (moth 2. WriteIUPAC given. names eachof the formulas for (a) CHl. (antiseptic) (b) cH, : c - cHrcl

ICH, (insecticide) (cJ CHrCl,(paintremover) (d) CHrBr-CHBr-CHrBr (soil fumigantl

Propertiesof OrganicHalidesThepresence the halogen of atom on a hydrocarbon chainor ring renders molecule the morepolar.This is because halogens more electronegative C and H atoms,and are than socarbon-halogen bondsaremorepolarthanC-H bonds. increased The polarityof allcyl halides increases strength the intermolecular the of forces. Thusalkylhalides havehigher boiling pointsthan the corresponding "like dissolves hydrocarbons. Because like,"the increased polarity alsomakes them moresolublein polar solvents than hydrocarbons of similarsize. When organichalidesare formed from halogenation hydrocarbons, product of the obtained often a mixture of halogenated is compounds. These compounds may contain 1,2,3,or morehalogens molecule, per reflecting intermediate that compounds can be further halogenated. molecules The that containmore halogen atomsareusually

Organic Compounds33

more polar than the lesshalogenated molecules, and thus havehigher boiling points (Tablef ). This difference boiling pointsconveniently in us enables to separate comthe ponentsof a mixture by procedures suchasfractionaldistillation. TableI Points Some Boiling of Hydrocarbons Corresponding and Halides OrganicBoillng polnt (oC) -24

HydrocarbcnCHa

czHo csHacqHro 78

The Gostof Air ConditioningThe costof a new carwith air conditioningincludesthe price of the unit plus an additional "air-conditioner"tax.On top of that,thereis another, obvious,cost:possible less environmental damage. ustakea look at how organicchemistrycanbe usedto solve Let someproblems,and how sometimes new problemsare created along the way. In the late 1800s, werecooledusingtoxic gases refrigerators suchas ammonia,methylchloride,and sulfur dioxide.Whenseveral fatalaccidentsoccurredin the 1920s a resultof leakedcoolant.the search as for began a safer refrigerant.In 1930 DuPontcompanymanufactured the (Industrial Freon,a chlorofluorocarbon, CF2Cl2(s), calledCFC-12. also chemists sometimes nameFreons usinga non-Sl system.) it was As inert, it wasconsidered very safeand its usespreadto aerosolsprays, paints,and many other applications. In the 1970s, in large"ozoneholes"weredetected the upper atmosphere, particularly It that overthe polar regions. appears althoughCFCs areinert in the loweratmosphere, arereactive the upperatmosthey in phere.In the presence UV light, CFCmolecules-includingFreonof decompose, releasing highly reactive chlorineatoms. The chlorinedestroys ozonemolecules the stratosphere, the in leavingus unprotected from harmfrrlI-IV radiation (Figure 1).You may havelearnedaboutthesereactions in a previouschemistrycourse. Automobileair conditioners useover one-third of the total amount of Freonin into Canada, about l0olo this total is released the atmosphere year. and of each Hence the search on againto find a new chemicalto meet the demandfor inexpensive is airconditioningsystems, to minimize environmental and damage. TWo tlpes of chemicals (HCFCs), havebeendeveloped substitute as refrigerants: hydrochlorofluorocarbons the (HFCs).Thesemoleculesdiffer from CFCsin that they and the hydrofluorocarbons containhydrogenatomsin addition to carbonand halogenatoms.The H atomsreact with hydroryl groupsin the atmosphere, decomposing molecules. the Since HCFCs the and HFCsreadilydecompose, havelesstime to cause they damage the ozonelayer. to Note that HCFCsstill containchlorine,the culprit in ozonedepletion; HFCscontainno chlorine and so are the preferredsubstitutefor CFCs.Thesemoleculesare more readily decomposed the lower atmosphere thus havelesstime to cause in damage. and However, they do release carbondioxide,a major greenhouse upon decomposition. gas, Themostcommonlyusedcoolantnow is HFC-134a. it Since1995, hasbeenusedin all new automobileair conditioners. 2001,the Ontario government In introducedlegislationrequiringthat all old units,whenrefillingis needed, adapted useoneof the be to new alternative refrigerants.

Figure I "hole"(blueJ An ozone formsover every the Antarctic spring (September October). and

34 Chapterl

Section1.4

s..f.i*'.llfijWUnderstandingGoncepts 3. Create flow chartoutlining effects an accidental of refrigerant a the of leak froma car's conditioner. air lnclude chemical equations wherever oossible. 4. Drawa timelineshowing useandeffects various the of refrigerants last150 overthe years. predicting decompositionHCFCs HFCs. 5. (a) Writechemical equations the of and (b) WhymightHCFCs HFCs and decompose morequickly thanCFCs? thismake themless damaging thanCFCs? [c) Whymight

RolePlay: CanWeAtrordAir Conditioning?Whena carmanufaclurer planning develop new model, is a to all aspects the vehicle reconsidered. of are Government regulationsprohibit manufacture newvehicles the of with air-conditioningunitsthat useCFCs. Alternative coolants havebeen developed, now mostmanufacturers HFC-l34a. and use gases However, HFCs greenhouses are and so,if released, are likelyto be contributors globalwarming. to lmagine that a committeeis set up to decide whetherthe nextnew modelshould air have conditioning usingHFC{34a, no air-conditioning or unit at all.Committee members include: unionrepresentative a forthe production-line workers; localMP;an environmenthe talist;a reporterfrom drivers' a magazine; physician; reprea a sentative fromthe Canadian Automobile Association; an advertising executive; shareholders the carcompany. in can be measured manyways: in financial, social, [a) Costs political, Choose way of environmental, etc. one

O Define lssue the O Analvze lssue the

Alternatives I Research O ldentify the O Defend Position O Evaluate

to cost assessing and collectand sort information help you decide air whether costsof automobile condithe are tioners justified. a who tbl Select roleforyourself-someone wouldbe concerned aboutthe kindsof coststhat you have Consider this person how mightfeelabout researched. of the issue airconditioning. (c) Role-play meeting, takinga turn to the with everyone position whether new car put forwardhis/her on the modelshouldhaveair conditioning. (dl Afterthe"meeting," and the discuss summarize most pointsmade. possible, lf important cometo a consensus issue. aboutthece. www.scien trelson.corn

PreparingOrganicHalidesAlkyl halidesare produced in halogenationreactionswith hydrocarbons,aswe learned in Section 1.3.Alkenes and alkynesreadily add halogensor hydrogen halides to their double and triple bonds. Recall also that Markovnikov's rule of "the rich get richer" applieswhen hydrogen halidesare reactants, and must be consideredin designingthe synthesisof specificalkyl halides.Thesealkyl halides can then be transformed into other organic compounds. An example of the halogenation of an alkyrre is shown below for a review of the reactions that produce alkyl halides.Thesereactionsreadily take placeat room temperature. la/ H-C:C-H+ilr ethYnel',r l,:

. C - H []r.---*H - C * bromine + 1,2-dibromoethene

3 O r g a n iC o m p o u n d s 5 c

(b)Learning Tip Several lettersymbols comare monly usedin general formulas to represent constituents of organic compounds: R represents alkylgroup any R', R",etc.(R-prime, R-double primeJ represent alkyl any groupdifferent from otherRs X represents halogen atom any group a Zl represents phenyl

Br

H-C=C-H+Br\-_______--l

t

Br

l

Br

Br

H-C-C-H Br

t

'f * ,2-dibromoethene bromine

Br

t

1,1,2,2-tetrabromoethane

If we wanted to produce a halide of a benzene ring, we would need to arrange a substitution reaction with a halogen. The following example illustrates the chlorination of benzenein the presenceofa catalyst.Further substitution can occur in the benzenering until all hydrogen atoms are replaced by halogen atoms.

f'a

* benzene chlorine-

v

+ cr-cl Fecr:. f^l-ct

v

+ H-cr

* chlorobenzene hydrogen chloride

Preparing Alkenesfrom Alkyl Halides: Elimination Reactionselimination reaction a type of organicreaction that results the in lossof a smallmolecule froma larger molecule; the removal e.9., of H" froman alkane

Allcylhalidescan eliminatea hydrogenand a halide ion from adjacent carbonatoms, forming a doublebond in their place,therebybecomingan alkene. The presence a of hydroxideion is required,asshownin the example below.This type of reaction,in which atoms ionsareremoved from a molecule, called eliminationreaction.Elimination is an or reactions alkyl halidesarethe most commonlyusedmethod of preparingalkenes. ofH

HMustard Gas gas is a toxicalkylhalide Mustard that was usedas a chemical weaponin WorldWarl. Whenthis compound inhaled, reacts is rapit idlywith watermolecules the in lungs, eliminating Thehigh HCl. concentrations hydrochloric of acid destroy lungtissue, to leading gas death.Mustard was banned in the 1980s a resultof international as treaties, nevertheless been but has usedsince. clcH,-cHrs- cH,-cH,cl

t t l C - C - C -H t t lH B r H2-bromopropane +

H

H

+

OH-+

hydroxide ion H H H

r

t

H-C:C-C H propene

- H +

l

H-O

+ Br-

+

H ion water + bromide

I

Organic HalidesFunctionalgroup: R-X Preparation: . alkenes alkynes-+ organichalides and addition reactions with halogens hydrogenhalides or . alkanes aromatics organichalides -+ and substitutionreactions with halogens hydrogenhalides or Pathwayto other groups: ' alkyl halides-> alkenes eliminationreactions, removinghydrogenand halideions

36 Chapter I

Section1.4

Understanding Concepts prod6. Classifythe as following substitution oradditionreactions. Predict possible all uctsforthe initialreaction the diaonly.Complete word equation the structural and gramequation eachcase. in Youneednot balance equations. the (a) trichloromethane chlorine-+ + (b) propene * bromine-+ (cJ ethylene+ hydrogen iodide --> (d) ethane + chlorine--> ---) (e) CI-C-C-Cl + F-F (excessJ ( f ) H H H H l l r l

H-c:c-9-g-Ht

+ H-cl ----)

l

H

H

ts) -,-\ (

| ( ) l+ cl-cl -+

/'-\Y

-Cl

vExtension

7. Whyaresomeorganic halides toxicwhileothers not?And why aresomeorganare ismsaffected morethanothers? the Internet find out,usingthe following Use key to bioaccumulation; soluble; wordsin yoursearch: fat foodchain. Report yourfindings on in a shortarticle a popular for science magazine web site. or

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Examples of one writea reportor present suchcasestudy. gasoline, of soluse leaded and unleaded topicsinclude; I. Drawstructural diagrams represent elimination the to reacpropellants, useof use and ventsin dry cleaning, of aerosol tion of2-chloropentane forman alkene. to Include reactants, pesticides fertilizers. and and all possibleproductsand their reactionconditions, gas weapon, both 5. Whywas mustard suchan effective IUPAC names. Research propits duringWorldWar1 and morerecently.2 2. Classify writestructural and formula equations forthe folhavebeendeveloped and ertiesand effects, what defences lowingorganic reactions: against it. -+ (a) propane chlorine * www.science. nelson.com * 1-chloropropane 2-chloropropane * hydrogen chloride --> (bJ propene bromine 1,2-dibromopropane * the was 6. Shortly aftertheconnection madebetween "hole" (c) benzene iodine-+ iodobenzene hydrogen * + of in the ozonelayer andthe release chlorofluorocarbons, iodide as in manymanufacturers stopped usingCFCs propellants Applying Inquiry Skills aerosol cans. (a) Research weredeveloped, the and what alternatives 3. Thesynthesis an organic of compound typically involves a Are of effectiveness eachin the marketplace. the alterseries reactions, example, of for somesubstitutions and still natives in use?Haveanyofthem beenfoundto some additions. causeproblems? (a) Plana reaction beginning with a hydrocarbon preto (bJ Design product(onethat mustbe sprayed under a pare1,1,2-trichloroethane. pressure) its packaging. Plana marketing strategy and (b) Whatexperimental complications mightarisein the is thathighlights wayin whichyourproduct attempting reactions the suggested part (aJ? in sprayed fromthe container. Understanding Goncepts

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Making Gonnections 4. Research examples the useof organic of chemistry to problems, safety, environmental address health, or and

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Compounds37 Organic

alcoholan organic compound characterized the presence a by of group; hydroxyl functional R-OH hydroxylgroup an -OH functional groupcharacteristic alcohols of Figure I Molecular models general and formulas (a) water, of H-O-H, (b) the simplest alcohol, CH3-OH, methanol (c) the simplest and ether, HsC- O- CH3, methoxymethane (dime