PowerPoint Presentation

Organic ChemistryCH. 25

DefinitionsOrganic means based on carbon Hydrogen, oxygen, and other elements are sometimes presentInorganic means all those compounds without carbonExceptions: Diamond, graphite, carbon dioxide

Whats So Special About Carbon?It can form 4 covalent bondsWith other carbon atomsWith other elementsForms long chains (straight or branched)Rings and hoopsTypes of Carbon AtomsPrimary carbon (1o)a carbon bonded to one other carbon

Secondary carbon (2o)a carbon bonded to two other carbons

Tertiary carbon (3o)a carbon bonded to three other carbons

Some organic chemicals

DNA

Essential oils

MedicinesActive Pharmaceutical IngredientsExcipients

Materials

Fuels

PigmentsHydrocarbonsCompounds which contain only carbon and hydrogenObtained from petroleum distillationFuels, solvents, lubricants, waxes, paving materialsStarting materials for countless other products

Hydrocarbons- TypesAliphaticLong chains (can be branched)

Alicyclic Rings or hoops

Aliphatic Hydrocarbons2 Types

Saturated (only single bonded carbons)

Unsaturated (can contain double or triple bonded carbons)

Saturated Hydrocarbons:AlkanesAll end in aneOnly single bondsGeneric formula CnH(2n+2) Known as a homologous series (add CH2 unit each time)Methane CH4 (Natural Gas)Propane C3H8 (common fuel gas)Butane C4H10 (common fuel gas)Gasoline (A mixture of liquid hydrocarbons from heptane C7H16 to Decane C10H22

Alkanes

The First 10 Normal AlkanesNameFormulaM.P.B.P.# Structural IsomersMethaneCH4-183-1621EthaneC2H6-172-891PropaneC3H8-187-421ButaneC4H10-138 02PentaneC5H12-130 363HexaneC6H14-95 685HeptaneC7H16-91 989OctaneC8H18-5712618NonaneC9H20-5415135DecaneC10H22-3017475C1 - C4 are Gases at Room TemperatureC5 - C16 are Liquids at Room TemperaturePrefixes for # of Carbons1Meth6Hex2Eth7Hept3Prop8Oct4But9Non5Pent10DecIUPAC Rules for Naming Branched AlkanesFind and name the parent chain in the hydrocarbon - this forms the root of the hydrocarbon nameNumber the carbon atoms in the parent chain starting at the end closest to the branchingName alkane branches by dropping the ane from the names and adding yl. A one-carbon branch is called methyl, a two-carbon branch is ethyl, etcWhen there are more than one type of branch (ethyl and methyl, for example), they are named alphabeticallyFinally, use prefixes to indicate multiple branches

Branched- ChainsDesignate the location (number of the carbon on the parent chain) for each attached group

1 2 3 4 5 2-methylSome Simple Alkanes2-methylpentane

3-ethylhexane

2,2-dimethylbutane

2,3-dimethylbutane

Example 1: 2,2-dimethylpentaneThe parent chain is indicated by the ROOT of the name - pentane. This means there are 5 carbons in the parent chain.

dimethyl tells us that there are TWO methyl branches on the parent chain. A methyl branch is made of a single carbon atom.

2,2- tell us that BOTH methyl branches are on the second carbon atom in the parent chain.

12345Example 2: 3-ethyl-2,4-dimethylheptaneThe parent chain is indicated by the ROOT of the name - heptane. This means there are 7 carbons in the parent chain.

2,4-dimethyl tells us there are TWO methyl branches on the parent chain, at carbons #2 and #4.

3-ethyl- tell us there is an ethyl branch (2-carbon branch) on carbon #3 of the parent chain.1234576

Example 3: 2,3,3-trimethyl-4-propyloctaneThe parent chain is indicated by the ROOT of the name - octane. This means there are 8 carbons in the parent chain.

2,3,3-trimethyl tells us there are THREE methyl branches - one on carbon #2 and two on carbon #3.

4-propyl- tell us there is a propyl branch (3-carbon branch) on carbon #4 of the parent chain.12345768

12345768

Example 4: Name the molecules shown!parent chain has 5 carbons - pentanetwo methyl branches - start counting from the right - #2 and #32,3-dimethylpentane

parent chain has 8 carbons - octanetwo methyl branches - start counting from the left - #3 and #4one ethyl branch - #5name branches alphabetically3,4-dimethyl43octane55-ethyl-Isomers Straight chain alkanes: An alkane that has all its carbons connected in a row. Branched chain alkanes: An alkane that has a branching connection of carbons.Structural IsomerismStructural isomers are molecules with the same chemical formulas but different molecular structures - different connectivity.They arise because of the many ways to create branched hydrocarbons.

n-pentane, C5H122-methlbutane, C5H1224

IsomersIsomers - organic molecules that have:Identical molecular formulas, butDiffering internal arrangement of atomsBiology, 9th ed,Sylvia MaderOrganic ChemistrySlide #24Chapter 03Different isomers are completely different compounds. They have different structures, different physical properties such as melting point and boiling point, and may have different physiological properties.

Isomers: carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane. Learning CheckDraw all possible structural isomers of C5H12

Unsaturated HydrocarbonsAlkenes1 Double BondHomologous Series remains the same, add CH2 each timeGeneric formula CnH2nEthene (C2H4) common name ethyleneButene (C4H8)2 double bonds are called Dienes3 double bonds are called TrienesUnsaturated HydrocarbonsAlkynesContains a triple bondNames end in -yneGeneric formula CnH(2n-2)Most Familiar example is ethyneCommon name acetylene C2H2Welding fuel kept dissolved in acetone

Naming Alkenes and AlkynesWhen the carbon chain has 4 or more C atoms, number the chain to give the lowest number to the double or triple bond. 1 2 3 4CH2=CHCH2CH31-buteneCH3CH=CHCH32-butene CH3CCCH32-butyne

Naming Alkenes and AlkynesWhen the carbon chain has 4 or more C atoms, number the chain to give the lowest number to the double or triple bond. 1 2 3 4CH2=CHCH2CH31-butene CH3CH=CHCH32-butene CH3CCCH32-butyne

Alicyclic Hydrocarbons2 typesSaturated ringsCyclohexane C6H12Aromatic ringsBenzeneC6H6

Alkanes - CycloalkanesA cycloalkane is made of a hydrocarbon chain that has been joined to make a ring.

Note that two hydrogen atoms were lost in forming the ring!

What is the general formula for a cycloalkane?CycloalkanesCycloalkanes: An alkane that contains a ring of carbon atoms. Ring sizes from 3 carbons to 30 or higher are known.

Drawing and Naming CycloalkanesCycloalkanes are represented by polygons. A triangle represents cyclopropane, a square represents cyclobutane, a pentagon represents cyclopentane, and so on.

Line structure: A shorthand way of drawing structures in which atoms arent shown; instead a carbon atom is understood to be at each corner and hydrogens are understood.

Step 1: Use the cycloalkane name as the parent chain.Step 2: Number the substituents starting at the group that has alphabetical priority, and proceed around the ring in the direction that gives the second substituent the lower possible number. Additional Rules for Naming CyclicsCycloalkanes with Side Groups

Learning CheckWrite the IUPAC name for each of the following unsaturated compounds:A.CH3CH2CCCH3

CH3

B. CH3C=CHCH3C.

Learning Check

Name those alkenes...

cis-4-methyl-2-pentene2-methyl-2-hexenecyclopentenecis-3-heptenetrans-2-bromo-3-methyl-2-penteneCis and Trans IsomersDouble bond is fixedCis/trans Isomers are possible

CH3 CH3 CH3

CH = CH CH = CH cis trans CH3Cis- and Trans- terminologyIf alkenes have two different substituents at each end of the C=C then they can exist as stereoisomers because there is restricted rotation of the double bond.

In cis isomers, two methyl groups are close together on the same side of the double bond.

In trans isomer, two methyl groups are far apart on opposite side of the double bond.

Both cis and trans isomers have the same formula and connections between the atoms but have different three dimensional structures because the way the groups are attached to the carbons.Cis-trans isomerism occurs in an alkene whenever each double bond carbon is bonded to two different substituent groups. Cis-trans isomerism is not possible if one of the double bond carbons is attached to two identical groups.

Name These

Aromatic Compounds and BenzeneAromatic compounds contain benzene. Benzene, C6H6 , is represented as a six carbon ring with 3 double bonds. Two possible resonance structures can be drawn to show benzene in this form.

Experimental evidence suggest that all six carbon-carbon bonds in benzene are identical.The properties, including the above one, of benzene can only be explained by assuming that the actual structure of benzene is an average of the above two possible equivalent structures-known as resonance.Simple aromatic compounds like benzene are non-polar, insoluble in water, volatile, and flammable.Unlike alkenes, several aromatic hydrocarbons are toxic. Benzene itself is implicated as a cancer causing chemical.Aromatic Compounds in Nature and HealthMany aromatic compounds are common in nature and in medicine.

Naming Aromatic CompoundsAromatic compounds are named with benzene as the parent chain. One side group is named in front of the name benzene. - No number is needed for mono-substituted benzene since all the ring positions are identical.

methylbenzenechlorobenzene (toluene)

Naming Aromatic CompoundsWhen two groups are attached to benzene, the ring is numbered to give the lower numbers to the side groups. The prefixes ortho (1,2), meta (1,3-) and para (1,4-) are also used.

Some Common NamesSome substituted benzene rings also use a common name. Then naming with additional more side groups uses the ortho-, meta-, para- system.

Many substituted aromatic compounds have common names in addition to their systematic names.

Learning CheckSelect the names for each structure:

a. Chlorocyclohexaneb. Chlorobenzenec. 1-chlorobenzene

a. Meta-xyleneb. Meta-dimethylbenzenec. 1,3-dimethylbenzene

New Attached GroupsPhenyl

Benzyl

Nitro -NO2

2,4,6-trinitrotoluene

Benzyl alcohol

4-phenyl-1-buteneRefer to your chart for order of priority!

Organic Chemistry:Functional Groups

21/10/99 Origin of organic compoundsNaturally occurring organic compounds are found in plants, animals, and fossil fuelsAll of these have a plant originAll of these rely on the fixing of C from CO2Synthetic organic compounds are derived from fossil fuels or plant material

21/10/99Organic reactions often much slower than inorganic reactionsmust break strong covalent bondtrying to find new catalysts to use Substitution Reactions- an atom (or group of atoms) replaces another atom or group of atomsSubstitution ReactionsA halogen (shown as X) can replace a hydrogen to make a halocarbon:R-H + X2 R-X + HXSunlight is often a sufficient catalyst:

CH4 + Cl2 CH3Cl + HClUV lightSUBSTITUTIONSATURATED COMPOUNDS ONLYONE KIND OF ATOM OR GROUP IS SUBSTITUTED WITH ANOTHER KIND OF ATOM OR GROUPPRODUCE HALIDESC4H10 + Cl2 C4H9Cl + HClTRY THESE!C3H8 + I2 C3H7I + HIC7H16 + F2 C7H15F + HFBE ABLE TO DRAW REACTANTS AND PRODUCTSBE ABLE TO NAME PRODUCTSAddition ReactionsThe carbon-carbon single bond is not easy to breakIn double bonded alkenes, it is easier to break a bondAddition reaction- substance is added at the double or triple bond location, after it is brokenAddition ReactionsIf a halogen is added in an addition reaction, the result is a halocarbon that is disubstituted - middle p. 734The addition of bromine is often used as a test for saturation - p.734Addition of a hydrogen halide? -called monosubstituted halocarbon ADDITION RxnsADDING 2 OR MORE ATOMS TO CARBON ATOMS THAT ARE ATTACHED TO OTHER CARBON ATOMS BY DOUBLE OR TRIPLE BONDS.OCCUR MORE EASILY THAN SUBSTITUTIONHOW HALIDES ARE MADEALKENES AND ALKYNESC6H12 + Cl2 C6H12Cl2TRY THESE!!C7H14 + Br2 C7H14Br2C3H6 + I2 C3H6I2BE ABLE TO DRAW AND NAME REACTANTS AND PRODUCTSPOLYMERIZATIONCONDENSATIONMONOMERS JOIN BY DEHYDRATION (DEHYDRATION SYNTHESIS).I.E. POLYESTERS, SILICONES, NYLONS, SOME PLASTICSADDITIONOPENING OF DOUBLE AND TRIPLE BONDS TO JOIN MONOMERS.I.E. VINYL PLASTICS LIKE POLYETHELENE AND POLYSTYRENE.LARGE MOLECULES(POLYMERS) ARE MADE FROM SMALLER MOLECULES CALLED MONOMERS.CAN BE NATURAL OR SYNTHETICPROTEINS, STARCHES,RUBBERNYLON, POLYESTER, RUBBERD. Polymers Polymers large chainlike molecules made from many small molecules called monomers Simplest polymer polyethylenePolyethylene results from addition polymerization.

69D. Polymers Condensation polymerization a small molecule (often water) is released for each addition of a monomer to the polymer chain Copolymer 2 different types of monomers combine to form the chain

Nylon70Functional GroupsMost organic chemistry involves substituentsoften contain O, N, S, or Palso called functional groups- they are the chemically functional part of the molecule, and are the non-hydrocarbon partFunctional GroupsFunctional group - a specific arrangement of atoms in an organic compound, that is capable of characteristic chemical reactions.What is the best way to classify organic compounds? By their functional groups.73Functional GroupsA functional group is an atom or a group of atoms with characteristic chemical and physical properties. It is the reactive part of the molecule.Most organic compounds have CC and CH bonds. However, many organic molecules possess other structural features:Heteroatomsatoms other than carbon or hydrogen. Bondsthe most common bonds occur in CC and CO double bonds.These structural features distinguish one organic molecule from another. They determine a molecules geometry, physical properties, and reactivity, and comprise what is called a functional group.Introduction to Organic Molecules and Functional Groups7374Heteroatoms and bonds confer reactivity on a particular molecule.Heteroatoms have lone pairs and create electron-deficient sites on carbon. Bonds are easily broken in chemical reactions. A bond makes a molecule a base and a nucleophile.

Dont think that the CC and CH bonds are unimportant. They form the carbon backbone or skeleton to which the functional group is attached.7475Polar; some sugarsExample: AcetonePolar, forms H-bonds; some sugarsand amino acids Example: EthanolROHRHCORRCOROHCORHNHRSHBiologically ImportantFunctional GroupsThiolsAminesAminoCarboxylicAcidsCarboxylKetonesAldehydesCarbonylAlcoholsHydroxylCompoundStructureGroupSignificancePolar; some sugarsExample: FormaldehydePolar, acidic; fats and amino acidsExample: Acetic acidPolar, basic; amino acidsExample: TryptophanDisulfide Bonds; some amino acidsExample: EthanethiolPolar, forms H-bonds; some sugarsand amino acids; Example: EthanolPolar; some sugarsExample: FormaldehydePolar; some sugarsExample: AcetonePolar, acidic; fats and amino acidsExample: Acetic acidDisulfide Bonds; some amino acidsExample: EthanethiolBiology, 9th ed,Sylvia MaderOrganic ChemistrySlide #75Chapter 03Functional Groups

Functional GroupsThe symbol R is used to represent any carbon chains or ringsAlcoholsAlcohols - a class of organic compounds with an -OH groupThe -OH functional group in alcohols is called a hydroxyl group; thus R-OH is the formulaHow is this different from the hydroxide ion? (covalent bonding with the carbon- not ionic with a metal like bases)AlcoholsAliphatic alcohols classified into categories according to the number of R groups attached to the carbon with the hydroxyl1 R group: primary alcohol2 R groups: secondary alcohol3 R groups: tertiary alcoholAlcoholsBoth IUPAC and common namesFor IUPAC:drop the -e ending of the parent alkane name; add ending of -ol, number the position of -OHparent is the longest chain that contains the carbon with the hydroxyl attached.AlcoholsThe hydroxyl is given the lowest position numberAlcohols containing 2, 3, and 4 of the -OH substituents are named diols, triols, and tetrols respectivelyAlcoholsCommon names:similar to halocarbons, meaning name the alkyl group, then followed by the word alcoholOne carbon alcohol = methyl alcoholAlcoholsMore than one -OH substituents are called glycols (ethylene glycol?)Phenols - compounds in which a hydroxyl group is attached directly to an aromatic ring. Cresol is the common name of o, m, and p isomers of methylphenolProperties of AlcoholsMuch like water, alcohols are capable of hydrogen bonding between moleculesthis means they will boil at a higher temp. than alkanes and halocarbons with a comparable number of atomsProperties of AlcoholsAlcohols are derivates of water; the -OH comes from water, and thus are somewhat solubleAlcohols of up to 4 carbons are soluble in water in all proportions; more than 4 carbons are usually less soluble, because the longer carbon chain is more nonpolarProperties of AlcoholsMany aliphatic alcohols used in laboratories, clinics, and industryIsopropyl alcohol (2-propanol) is rubbing alcohol; used as antiseptic, and a base for perfume, creams, lotions, and other cosmeticsEthylene glycol (1,2-ethanediol) - commonly sold as antifreezeProperties of AlcoholsGlycerol (1,2,3-propanetriol) - used as a moistening agent in cosmetics, foods, and drugs; also a component of fats and oilsEthyl alcohol (ethanol) used in the intoxicating beverages; also an important industrial solventProperties of AlcoholsDenatured alcohol- means it has been made poisonous by the addition of other chemicals, often methyl alcohol (methanol, or wood alcohol).As little as 10 mL of methanol has been known to cause permanent blindness, and 30 ml has resulted in death!EthersA class of organic compounds in which oxygen is bonded to 2 carbon groups: R-O-R is formulaNaming? The two R groups are alphabetized, and followed by etherTwo R groups the same? Use the prefix di-EthersDiethyl ether is the one commonly called just etherwas the first reliable general anestheticdangerous- highly flammable, also causes nauseaethers are fairly soluble in waterAldehydes and KetonesReview:alcohol has an oxygen bonded to a carbon group and a hydrogenether has an oxygen bonded to two carbon groupsAn oxygen can also be bonded to a single carbon by a double bondAldehydes and KetonesThe C=O group is called the carbonyl groupit is the functional group in both aldehydes and ketonesAldehydes - carbonyl group always joined to at least one hydrogen (meaning it is always on the end!)

A. Aldehydes and Ketones Aldehyde carbonyl group always appears on the end of the hydrocarbon chain and has at least one H atom bonded to the carbonyl group

93Aldehydes and KetonesKetones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end)

Aldehydes and KetonesNaming?Aldehydes: identify longest chain containing the carbonyl group, then the -e ending replaced by -al, such as methanal, ethanal, etc.

Ketones: longest chain w/carbonyl, then new ending of -one; number it?propanone, 2-pentanone, 3-pentanoneAldehydes and KetonesNeither can form intermolecular hydrogen bonds, thus a much lower b.p. than corresponding alcoholswide variety have been isolated from plants and animals; possible fragrant odor or taste; many common namesAldehydes and KetonesBenzaldehydeCinnamaldehydeVanillinMethanal (the common name is: formaldehyde)40% in water is formalin, a preservativeAldehydes and KetonesPropanone (common: acetone) is a good solvent; miscible with water in all proportionswhy is it a good substance used in nail-polish removers? (a powerful solvent-able to dissolve both polar & nonpolar)The Carboxylic AcidsAlso have a carbonyl group (C=O), but is also attached to a hydroxyl group (-OH) = carboxyl groupgeneral formula: R-COOHweak acids (ionize slightly)Named by replacing -e with -oic and followed by the word acidmethanoic acid; ethanoic acid

Carboxylic AcidsAbundant and widely distributed in nature, many having a Greek or Latin word describing their originacetic acid (ethanoic acid) from acetum, meaning vinegarmany that were isolated from fats are called fatty acidsC. Carboxylic Acids and Esters

103The EstersGeneral formula: RCOORDerivatives of the carboxylic acids, in which the -OH from the carboxyl group is replaced by an -OR from an alcohol:carboxylic acid + alcohol ester + watermany esters have pleasant, fruity odors- banana, pineapple, perfumesC. Carboxylic Acids and Esters Esters a carboxylic acid reacts with an alcohol to form an ester and a water molecule

General formula

105C. Carboxylic Acids and Esters To name esters Use the alkyl name from the alcohol followed by the acid name, where the ic ending is replaced by ate.isopropylethanoate

106EstersAlthough polar, they do not form hydrogen bonds (reason: there is no hydrogen bonded to a highly electronegative atom!)thus, much lower b.p. than the hydrogen-bonded carboxylic acids they came fromEstersCan be prepared from a carboxylic acid and an alcohol; usually a trace of mineral acid added as catalyst (because acids are dehydrating agents)EstersNaming? It has 2 words:1st: alkyl attached to single bonded oxygen from alcohol2nd: take the acid name, remove the -ic acid, add -ateOrganic NomenclatureSuffixes/Meanings I-ane Alkane (saturated hydrocarbon)-ene Alkene (one double bond) -yne Alkyne (one triple bond)-ine organic amine (amphetamine, caffeine, cocaine, morphine, heroin)-one Ketone (acetone, nail polish remover)

Organic NomenclatureSuffixes/Meanings II-ase Enzymes ( protein catalysts in biochemical reactions)-oseSugars(glucose, sucrose)-olAlcohols-alAldehydes (formaldehyde)-ateEsters(many flavors and fragrances)-adeSomething to drink