copyright 2011 pearson education, inc. chapter 20 organic chemistry roy kennedy massachusetts bay...

Copyright 2011 Pearson Education, Inc.

Chapter 20Organic

Chemistry

Roy KennedyMassachusetts Bay Community College

Wellesley Hills, MA

Chemistry: A Molecular Approach, 2nd Ed.Nivaldo Tro


Odors• Our sense of smell helps us identify food, people, and

other organisms, and alerts us to dangers such as polluted air or spoiled food

• Odorants must be volatile

• However, many volatile substances have no scent at all

• Most common smells are caused by organic molecules

• The study of compounds containing carbon combined with one or more of the elements hydrogen, nitrogen, oxygen, and sulfur, including their properties and their reactions, is known as organic chemistry

Tro: Chemistry: A Molecular Approach, 2/e 2


What Is Organic Chemistry?

• Organic chemistry is a branch of chemistry that focuses on compounds that contain carbonexcept CO, CO2, carbonates, and carbides

• Even though organic compounds only contain a few elements, the unique ways carbon atoms can attach together to form molecules leads to millions of different organic compounds

4Tro: Chemistry: A Molecular Approach, 2/e


The Chemistry of Life

• Life as we know it is because of organic chemistry

• Organic molecules can be very large and complex

• It is this complexity of large organic molecules that allows the complex functions of the cells to occur



Differences Between Organic and Inorganic Compounds

• Organic compounds are easily decomposed into simpler substances by heating, but inorganic substances are not

• Inorganic compounds were readily synthesized in the lab, but synthesis of organic compounds in the lab is hard



What’s Special About Organic Compounds?

• Organic compounds tend to be molecular• Mainly composed of just six nonmetallic elements

C, H, O, N, S, and P

• Compounds found in all three statessolids, liquids, and gasessolids tend to have low melting points

• Solubility in water varies depending on which of the other elements are attached to C and how many there areCH3OH is miscible with water; C10H21OH is insoluble



What’s So Special About Carbon?

• Carbon atoms can do some unique things that other atoms cannot

• Carbon can bond to as many as four other atoms

• Bonds to carbon are very strong and nonreactive

• Carbon atoms can attach together in long chains

• Carbon atoms can attach together to form rings

• Carbon atoms can form single, double, or triple bonds



Bond Energies and Reactivities



Carbon Bonding

• Carbon forms four bonds

• When C has four single bonds, the shape is tetrahedral

• When C has one triple + one single or two double bonds, the shape is linear

• When C has two single + one double bond, the shape is trigonal planar



linear, sp

all tetrahedral, sp3

Practice – Predict the shape and hybridization around each C aAtom

trigonal planar, sp2

CH3CN

CH3CH2CH3

H2CNH



Hydrocarbons

• Hydrocarbons contain only C and H aliphatic or aromatic

• Insoluble in waterno polar bonds to attract water molecules

• Aliphatic hydrocarbons saturated or unsaturated aliphatics

saturated = alkanes, unsaturated = alkenes or alkynes may be chains or ringschains may be straight or branched

• Aromatic hydrocarbons



Uses of Hydrocarbons



Physical Properties of Aliphatic Hydrocarbons

• Boiling points and melting points increase as the size of the molecule increasesnonpolar moleculesmain attractive forces are dispersion forces

• Less dense than water

• Insoluble in water



Saturated Hydrocarbons

• A saturated hydrocarbon has all C─C single bondsit is saturated with hydrogens

• Saturated aliphatic hydrocarbons are called alkanes

• Chain alkanes have the general formula CnH2n+2

• Ring alkanes have all C─C single bonds, but have fewer hydrogens than a chain with the same number of carbons



Unsaturated Hydrocarbons

• Unsaturated hydrocarbons have one or more C=C double bonds or CC triple bonds

• Unsaturated aliphatic hydrocarbons that contain C=C are called alkenes the general formula of a monounsaturated chain alkene

is CnH2n

remove two more H for each additional double bond

• Unsaturated aliphatic hydrocarbons that contain CC are called alkynes the general formula of an alkyne with one triple bond is

CnH2n−2

remove four more H for each additional triple bond



Aromatic Hydrocarbons

• Aromatic hydrocarbons contain a ring structure that seems to have C=C, but doesn’t behave that way

• The most prevalent example is benzene.C6H6

Other compounds have the benzene ring with other groups substituted for some of the Hydrogens


Copyright 2011 Pearson Education, Inc.19Tro: Chemistry: A Molecular Apprach

alkanes

Tro: Chemistry: A Molecular Approach, 2/e


Practice—Assuming only chains with a maximum of one unsaturation, decide if each of the following molecular formulas represents an

alkane, alkene, or alkyne

C14H28

C25H52

C12H22

Alkene

Alkane

Alkyne



Formulas• Molecular formulas just tell you what

kinds of atoms are in the molecule, but they don’t tell you how they are attached

• Structural formulas show you the attachment pattern in the molecule

• Models not only show you the attachment pattern, but give you an idea about the shape of the molecule



Condensed Structural Formulas

• Attached atoms listed in order central atom with attached atoms

• Follow normal bonding patterns use to determine position of multiple bonds

• () used to indicate more than one identical group attached to same previous central atom unless () group listed first in which case

attached to next central atom



Example – Write the structural and condensed formula for the n-Alkane C8H18

• Connect the C atoms in a rowCarbon backbone

• Add H to complete four bonds on each C.middle C gets 2 Hs end C gets 3 Hs

• The condensed formula has the H attached to each C written directly after it



Example – Draw a complete structural formula for CH2CHCH2CH(CH3)CH2CH3

25

start by writing the first C with its attached H’scontinue adding each successive C with its

attached H’s or branch chainsafter the entire chain is constructed, apply the rule

4 bonds per C to identify double or triple bonds



Practice – Write a complete structural formula for the straight chain isomer of C7H16



Practice – Draw a complete structural formula for CHCCH2C(CH3)2CH3



Carbon Skeleton Formulas

• Each angle, and beginning and end, represent a C atom

• H omitted on Cincluded on functional groups

• Multiple bonds indicateddouble line is double bond, triple line is triple bond



Practice – Draw a complete structural formula for each of the following



Formulas



Isomerism• Isomers are different molecules with the same molecular

formula• Structural isomers are isomers that have a different pattern of

atom attachmentaka Constitutional Isomers

• Stereoisomers are isomers with the same pattern of atom attachments, but the atoms have a different spatial orientation



Structural Isomers of C4H10

Butane, BP = 0 °C Isobutane, BP = −12 °C



Rotation about a Bond Is Not Isomerism



Possible Structural Isomers


Copyright 2011 Pearson Education, Inc.35

Example 20.1: Write the structural formula and carbon skeleton formula for C6H14

start by connecting the carbons in a line

determine the C skeleton of the other isomers



fill in the H to give each carbon four bonds

36

Example 20.1: Write the structural formula and carbon skeleton formula for the 5 structural isomers of C6H14



convert each to a carbon skeleton formula – each bend and the ends represent C atoms

37

n-hexaneBP 69 ºC

2-methylpentaneBP 60 ºC

3-methylpentaneBP 63 ºC

2,2-dimethylbutaneBP 50 ºC

2,3-dimethylbutaneBP 58 ºC

Example 20.1: Write the structural formula and carbon skeleton formula for the 5 structural isomers of C6H14



Practice – Draw the three structural isomers of pentane



Stereoisomers

• Stereoisomers are different molecules whose atoms are connected in the same order, but with a different spatial direction

• Optical isomers are stereoisomers that are nonsuperimposable mirror images of each other

• Geometric isomers are stereoisomers that are not optical isomers



Nonsuperimposable Mirror Images

the mirror image cannot be rotated so all its atoms align with the same atoms of the original molecule



Chirality

• Any molecule with a nonsuperimposable mirror image is said to be chiral

• Any carbon with 4 different substituents will be a chiral center

• A pair of nonsuperimposable mirror images are called a pair of enantiomers



Optical Isomers of 3-methylhexane



Practice – Draw the mirror image of the molecule and decide if they are enantiomers

Enantiomers



Plane Polarized Light

• Light that has been filtered so that only those waves traveling in a single plane are allowed through



Optical Activity• Enantiomers have all the same physical

properties except one – the direction they rotate the plane of plane-polarized lighteach one of the enantiomers will rotate the plane

the same amount, but in opposite directionsdextrorotatory = rotates the plane to the rightlevorotatory = rotates the plane to the left



Mixtures of Enantiomers

• An equimolar mixture of a pair of enantiomers is called a racemic mixture

• Because half the molecules are rotating the plane to the left and the other half are rotating it to the right, the rotations cancel, and the racemic mixture does not rotate the plane

• If the mixture is non-racemic, the amount of rotation can be used to determine the percentages of each enantiomer in the mixture



Chemical Behavior of Enantiomers

• A pair of enantiomers will have the same chemical reactivity in a non-chiral environment

• But in a chiral environment they may exhibit different behaviorsenzyme selection of one enantiomer of a pair



Alkanes

• Aka paraffins

• Aliphatic

• General formula CnH2n+2 for chains

• Very unreactive

• Come in chains or/and ringsCH3 groups at ends of chains, CH2 groups in the middle

• Saturated

• Branched or unbranched



Physical Properties of n–Alkanes



Alkane Boiling Points

• Branched chain alkanes have lower boiling points than straight chain alkanes

• Ring alkanes have higher boiling points than straight chain alkanes



Naming• Each name consists of three parts

prefix indicates position, number, and type of branches indicates position, number, and type of each functional group

parentindicates the length of the longest carbon chain or ring

suffixindicates the type of hydrocarbon

o ane, ene, yne

certain functional groups



Naming Alkanes

1. Find the longest continuous carbon chain2. Number the chain from end closest to a branch

if first branches equal distance use next in

3. Name branches as alkyl groups locate each branch by preceding its name with the carbon

number on the chain

4. List branches alphabetically do not count n-, sec-, t-, count iso

5. Use prefix if more than one of same group present di, tri, tetra, penta, hexa do not count in alphabetizing



Prefixes



Alkyl Groups



More Alkyl Groups



Examples of Naming Alkanes



1. Find the longest continuous C chain and use it to determine the base name

Example – Name the alkane

because the longest chain has 5 Cthe base name is pentane



2. Identify the substituent branches


there are 2 substituentsboth are 1 C chains, called methyl



3. Number the chain and substituents

a) determine the end closest to a substituent branch if first substituents equidistant from end, go to next substituent in

b) then assign numbers to each substituent based on the number of the main chain C it is attached to


both substituents are equidistant from the end

1 2 3 4 5

2 460Tro: Chemistry: A Molecular Approach, 2/e


Example – Name the alkane4. Write the name in the following order

a) substituent number of first alphabetical substituent followed by dashb) substituent name of first alphabetical substituent followed by a dash

if it is the last substituent listed, no dash use prefixes to indicate multiple identical substituents

c) repeat for other substituents alphabeticallyd) name of main chain

2 4

2,4 – dimethylpentane



Practice – Name the following

3-ethyl-2-methylpentane



Practice – Draw and name all nine structural isomers of heptane



Practice – Draw and name all ninestructural isomers of heptane

• The prefix hept- means 7, so the molecular formula is C7H16

• Start by drawing the carbon skeleton of the straight chain isomer




• Take one C off the right end of the straight chain isomer and attach it to the second C in from the left end

• Then keep moving it down the chain, but not past the halfway point




• Take one C off the right end of each one-branch chain isomer and attach it to the second C in from the left end

• Then keep moving it down the chainalways keep checking to ensure you do not duplicate

already have




• Take one C chain off the right end of 2,2-branch isomer and attach it to the third C in from the left end

• Then keep moving it down the chain• Repeat with other two branch isomers if necessary




• Take two C chain off the right end of straight chain isomer and attach it to the third C in from the left end

• Then keep moving it down the chain, but not beyond halfway




• Continue the process until you’ve drawn all the isomers




• Find the base name of each main chain

Heptane

Hexanes

Pentanes

Butane70Tro: Chemistry: A Molecular Approach, 2/e



• Number the main chain from end closest to a substituent

1 2 3 4 5 6 7

1 2 3 4 5 6 1 2 3 4 5 6

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

1 2 3 4 51 2 3 4 5

1 2 3 4

71

Hexanes




• Name and number the alkyl groups

heptane

2-methylhexane 3-methylhexane

2,2-dimethylpentane 2,3-dimethylpentane 2,4-dimethylpentane

3,3-dimethylpentane3-ethylpentane

2,2,3-trimethylbutaneTro: Chemistry: A Molecular Approach, 2/e



• Fill in the hydrogens so each C has four bonds



Drawing Structural Formulas

• Draw and number the base chain carbon skeleton

• Add the carbon skeletons of each substituent on the appropriate main chain C

• Add in required H’s

4-ethyl-2-methylhexane



Practice – Draw the structural formula of 4-isopropyl-2-methylheptane



Alkenes

• Also known as olefins• Aliphatic, unsaturated

C=C double bonds

• Formula for one double bond = CnH2n

subtract 2 H from alkane for each double bond

• Trigonal shape around Cflat

• Polyunsaturated = many double bonds



Double Bonds• sp2, trigonal planar

shorter bond lengthsalkene angles a little larger than 120°

• No free rotation around double bond

• Composed of 1sigma and 1 pi () bond

• Not twice as strong as single bond, therefore less stable and more reactive



Alkenes

ethene = ethylene propene = propylene

produced by ripening fruit

C CH

H H

HC C

H

H CH3

H

used to make polyethylene used to make polypropylene



Physical Properties of Alkenes



Physical Properties of Alkenes• pi bond electrons not held as tight as sigma,

therefore alkenes are more polarizable than alkanes

• cis generally more polar than trans

• trans lower boiling point

• more carbon groups attached to the double bond = higher boiling pointfor equal numbers of C

• densities similar to alkanes

• trans higher melting point than cismolecules are more symmetrical and pack better



Alkynes• Also known as acetylenes

• Aliphatic, unsaturated

• CC triple bond

• Formula for one triple bond = CnH2n−2

subtract 4 H from alkane for each triple bond

• Linear shape

• Internal alkynes have both triple bond carbons attached to C

• Terminal alkynes have one carbon attached to H



Triple Bonds

• sp hybrid50% “s” character

• Linear, 180°

• Composed of 2 pi bonds and 1 sigma

• Shorter than C–C and C=C

• Stronger than C–C, but not 3x as strongCC = 836 kJ/mol, C–C = 368 kJ/mol



Alkynes

both used in welding torches



Physical Properties of Alkynes



Physical Properties of Alkynes

• Higher boiling points than similar sized alkenessimilar size = same number of carbonsmore pi bond = more polarization = higher boiling

point

• Slightly higher densities than similar alkenes

• There are no alkyne cis or trans isomers

• Internal alkynes have higher boiling points than terminal alkyneswith the same number of C



Naming Alkenes and Alkynes

• Change suffix on main name from -ane to -ene for base name of alkene, or to -yne for the base name of the alkyne

• Number chain from end closest to multiple bond

• Number in front of main name indicates first carbon of multiple bond



Examples of Naming Alkenes



Examples of Naming Alkynes



Name the Alkene1. Find the longest, continuous C chain that

contains the double bond and use it to determine the base name

Because the longest chain with the double bond has6 C the base name is hexene




Name the Alkene

there are 2 substituentsone is a 1 C chain, called methyl

the other one is a 2 C chain, called ethyl



b) then assign numbers to each substituent based on the number of the main chain C it is attached to

Name the Alkene

1234

5 6

4

3

93

3. number the chain and substituents

a) determine the end closest to the double bond if double bond equidistant from both ends, number

from end closest to the substituents



Name the Alkene4. Write the name in the following order

a. substituent number of first alphabetical substituent – substituent name of first alphabetical substituent – use prefixes to indicate multiple identical

substituentsb. repeat for other substituentsc. number of first C in double bond – name of main chain

3–ethyl–4–methyl–2–hexene

94

1234

5 6

4

3




3,4-dimethyl-3-hexene

12

3 4 5 6



Name the Alkyne1. Find the longest, continuous C chain that

contains the triple bond and use it to determine the base name

Because the longest chain with the triple bond has 7 C the base name is heptyne




Name the Alkyne

there are 2 substituentsone is a 1 C chain, called methylthe other one is called isopropyl



Name the Alkyne

98

46

1234567

3. number the chain and substituents

a. determine the end closest to the triple bond if triple bond equidistant from both ends, number

from end closest to the substituents

b. then assign numbers to each substituent based on the number of the main chain C it is attached to



Name the Alkyne4. write the name in the following order

a) substituent number of first alphabetical substituent – substituent name of first alphabetical substituent – use prefixes to indicate multiple identical

substituentsb) repeat for other substituentsc) number of first C in triple bond – name of main chain

4–isopropyl–6–methyl–2–heptyne46

1234567



Practice – Name the Following

3,3-dimethyl-1-pentyne

123

4 5



Geometric Isomerism

• Because the rotation around a double bond is highly restricted, you will have different molecules if groups have different spatial orientation about the double bondstereoisomers

• This is often called cis–trans isomerism

• When groups on the doubly bonded carbons are cis, they are on the same side of the double bond

• When groups on the doubly bonded carbons are trans, they are on opposite sides



Cis–Trans Isomerism



Free Rotation Around C─C:No Cis–Trans Isomerism



No Free Rotation C=C:Cis-Trans Isomerism



Cis-Trans Isomerism

106

The cis and trans isomers are different molecules with different properties.



Reactions of Hydrocarbons

• All hydrocarbons undergo combustion

• Combustion is always exothermicabout 90% of U.S. energy generated by combustion

2 CH3CH2CH2CH3(g) + 13 O2(g) → 8 CO2(g) + 10 H2O(g)

CH3CH=CHCH3(g) + 6 O2(g) → 4 CO2(g) + 4 H2O(g)

2 CH3CCCH3(g) + 11 O2(g) → 8 CO2(g) + 6 H2O(g)



Chemical Energy• Burning hydrocarbons releases heat and light

energyCombustion

• Alkane + oxygen carbon dioxide + water• Larger alkane, more heat released



Other Alkane Reactions

• Substitutionreplace H with a halogen atominitiated by addition of energy in the form of

heat or ultraviolet light to start breaking bonds

generally get multiple products with multiple substitutions



Predict the Products and Balance the Equations



Other Alkene and Alkyne Reactions:Addition

• Adding a molecule across the multiple bond

• Hydrogenation = adding H2

converts unsaturated molecule to saturatedalkene or alkyne + H2 → alkane

generally requires a catalyst

• Halogenation = adding X2

• Hydrohalogenation = adding HXHX is polarwhen adding a polar reagent to a double or

triple bond, the positive part attaches to the carbon with the most H’s



Addition Reactions



Practice — Predict the products



Aromatic Hydrocarbons

• Contain benzene ring structure

• Even though they are often drawn with C=C, they do not behave like alkenes



Resonance Hybrid

• The true structure of benzene is a resonance hybrid of two structures



Naming Monosubstituted Benzene Derivatives

• (name of substituent)benzenehalogen substituent = change ending to “o”

• or name of a common derivative



Naming Benzene as a Substituent

• When the benzene ring is not the base name, it is called a phenyl group



Naming Disubstituted Benzene Derivatives

• Number the ring starting at attachment for first substituent, then move toward secondorder substituents alphabeticallyuse “di” if both substituents are the same



Naming Disubstituted Benzene Derivatives

• Alternatively, use relative position prefixortho- = 1,2; meta- = 1,3; para- = 1,4

2-chlorotolueneortho-chlorotoluene

o-chlorotoluene

3-chlorotoluenemeta-chlorotoluene

m-chlorotoluene

4-chlorotoluenepara-chlorotoluene

p-chlorotoluene



Practice – Name the Following

1-chloro-4-fluorobenzene 1,3-dibromobenzeneor meta-dibromobenzene

or m-dibromobenzene



Polycyclic Aromatic Hydrocarbons

• Contain multiple benzene rings fused togetherfusing = sharing a common bond



Functional Groups• Other organic compounds are hydrocarbons in which

functional groups have been substituted for hydrogens

• A functional group is a group of atoms that show a characteristic influence on the properties of the moleculegenerally, the reactions that a compound will perform are

determined by what functional groups it hasbecause the kind of hydrocarbon chain is irrelevant to the

reactions, it may be indicated by the general symbol R

CH3—OHR group functional group



Alcohols• R—OH• Ethanol = CH3CH2OH

grain alcohol = fermentation of sugars in grains

alcoholic beveragesproof number = 2x percentage of alcohol

gasohol• Isopropyl alcohol = (CH3)2CHOH

2-propanol rubbing alcoholpoisonous

• Methanol = CH3OHwood alcohol = thermolysis of woodpaint solventpoisonous



Naming Alcohols• Main chain contains OH• Number main chain from end closest to OH• Give base name ol ending and place number of C on

chain where OH attached in front • Name as hydroxy group if higher precedence group

present

1 2 3 4 5 6

4-ethyl-4-methyl-3-hex-5-enol




126

3-ethyl-1-hexanol

1 2 3

4 5 6

12345

1-pent-4ynol



Reactions of Alcohols

127

Nucleophilic substitutionCH3─OH + HCl CH3Cl + H2O

Acid catalyzed elimination (dehydration)

CH3─ CH2OH CH2═CH2 + H2OH2SO4



Reactions of Alcohols

128

Oxidation

CH3CH2OH CH3CHO CH3COOH −2 H −2 H

a common oxidizing agent is Na2Cr2O7

Alcohols with very active metals

2 CH3─OH + 2 K 2 CH3O−K+ + H2



Practice − Complete each reaction



Aldehydes and Ketones• Contain the carbonyl group• Aldehydes = at least 1 side H• Ketones = both sides R groups• Many aldehydes and ketones have

pleasant tastes and aromas• Some are pheromones

• Formaldehyde = H2C=Opungent gas formalin = a preservativewood smoke, carcinogenic

• Acetone = CH3C(=O)CH3

nail-polish remover



Aldehyde Odors and Flavors

132

• butanal = butter

• vanillin = vanilla

• benzaldehyde = almonds

• cinnamaldehyde = cinnamon



• acetophenone = pistachio

• carvone = spearmint

• ionone = raspberries

• muscone = musk

Ketone Odors and Flavors



Naming Aldehydes and Ketones• Main chain contains C=O

unless COOH present

• Number main chain from end closest to C=O

• For aldehydes, give base name al ending always on C1

• For ketones, give base name one ending and place number of C on chain where C=O attached in front




135

4-methyl-3-hexenal

12345

12

34 5

5-hydroxy-3-isopropyl-4-methyl-2-hexanone

6



Reactions• Aldehydes and ketones are generally

synthesized by the oxidation of alcohols

• Therefore, reduction of an aldehyde or ketone results in an alcohol

• Common reducing agents are H2 with a Ni catalyst, NaBH4, and LiAlH4



Carbonyl Group

C=O group is highly polarmany reactions involve addition across C=O,

with positive part attached to O



Addition to C=O

138

polar molecules add across the C=O, with the positive part attaching to O

−



Carboxylic Acids

140

• RCOOH• Sour tasting• Weak acids• Citric acid

found in citrus fruit

• Ethanoic acid = acetic acidvinegar

• Methanoic acid = formic acidinsect bites and stings



Synthesis of Carboxylic Acids

• Made by the oxidation of aldehydes and alcohols



Naming Carboxylic Acids

• Carboxylic acid group always on end of main chainhas highest naming precedence of functional groups

• C of group always C1position not indicated in name

• Change ending to oic acid



Examples of Naming Carboxylic Acids




144

hexanoic acid(aka caproic acid, which

causes foot odor)

2-hydroxy-3-methylbutanoic acid



Esters

• R–COO–R

• Sweet odor

• Made by reacting carboxylic acid with an alcohol

RaCOOH + RbOH RaCOORb + H2O



Naming Esters

• Carboxylic acid group always on end of main chainunless carboxylic acid group present

• C of ester group on C1position not indicated in name

• Begin name with alkyl group attached to O

• Name main chain with oate ending



Naming Esters




148

isopropyl butanoate



• Acid anhydrides are made by the condensation reaction between 2 carboxylic acid molecules

the reaction is driven by heat

R C

O

OH OH C

O

R' R C

O

O C

O

R'

+ + HOH

Condensation Reactions• A condensation reaction is any organic reaction

driven by the removal of a small molecule, such as water

149

• Esters are made by the condensation reaction between a carboxylic acid and an alcohol

the reaction is acid catalyzed



Synthesis of Aspirin(Acetylsalicylic Acid)



Practice – Complete the reaction



Ethers

152

• R–O–R

• Ether = diethyl ether = CH3CH2OCH2CH3

anesthetic

• Polar molecules

• Used for solvents

• To name ethers, name each alkyl group attached to the O, then add the word ether to the end




153

isopropyl methyl ether



Amines• N containing organic molecules• Very bad smelling• Form when proteins decompose• Organic bases• Name alkyl groups attached to the N, then

add the word amine to the end




155

isopropyl methyl amine



Amines• Many amines are biologically active

dopamine – a neurotransmitterepinephrine – an adrenal hormonepyridoxine – vitamin B6

• Alkaloids are plant products that are alkaline and biologically active toxicconiine from hemlockcocaine from coca leavesnicotine from tobacco leavesmescaline from peyote cactusmorphine from opium poppies



Amine Reactions

• Weak basesreact with strong acids to form ammonium salts

RNH2 + HCl → RNH3+Cl−

• React with carboxylic acids in a condensation reaction to form amides

RCOOH + H—NHR’ RCONHR’ + H2O



Practice – Complete the reaction



Polymers



Macromolecules• Polymers are very large molecules made by repeated

linking together of small molecules monomers

• Natural polymers are polymers found in both the living and nonliving environment

• Modified natural polymers are natural polymers that have been chemically altered

• Synthetic polymers are polymers made in a lab from one, two, or three small molecules linked in a repeating pattern plastics, elastomers (rubber), fabrics, adhesives

• Composites are materials made of polymers mixed with various additives additives such as graphite, glass, metallic flakes



Natural Polymers• Polysaccharides – polymers made of repeating small sugar

molecule units cellulose (cotton) starch

• Proteins – polymers made of repeating amino acid units• Nucleic acids (DNA) – polymers made of repeating nucleotide units

• Natural latex rubber – polyisoprene• Shellac – a resin secreted by lac bugs• Gutta-percha – a polyisoprene latex from the sap of the gutta-

percha plant used to fill space for root canal

• Amber, lignin, pine rosin – resins from trees• Asphalt – polymeric petroleum



Modified Natural Polymers

• Cellulose acetate – an ester of cellulose and acetic acid rayon film

• Vulcanized rubber – latex rubber hardened by cross-linking with sulfur

• Nitrocellulose – an ester of cellulose with nitric acid gun cotton celluloid

ping-pong balls

• Casein – a polymer of the protein casein made by treating cow’s milk with acid buttons, mouldings, adhesives



Polymerization

• Polymerization is the process of linking the monomer units together

• There are two processes by which polymerization may proceed – addition polymerization and condensation polymerization

• Monomer units may link head-to-tail, or head-to-head, or tail-to-tail during polymerizationhead-to-tail most common regular pattern gives stronger attractions between

chains than random arrangements



Addition Polymerization

• Monomers add to the growing chain in such a manner that all the atoms in the original monomer wind up in the chainno other side products formed, no atoms

eliminated

• First monomer must “open” to start reactiondone with heat, or the addition of an initiator

• The process is a chain reactioneach added unit ready to add another



Addition Polymerization of Vinyl Chloride



Condensation Polymerization

• Monomer units are joined by removing small molecules from the combining unitspolyesters, polyamides lose water

• No initiator needed

• The process is a chain reaction

• Each monomer has two reactive ends, so chain can grow in two directions



Condensation Polymerization



Plastics• Plastics are polymer materials capable of being

molded or shaped.Round, hard balls; thin, flexible threads; intricate

molds; or flat sheets.• Plastics have molar mass from 10,000 to

1,000,000 amu• Many plastics are in the “glass” or amorphous

solid statesolid that has semi-fluid characteristicsglass transition temperature is where an

amorphous polymer is converted between rubbery and glassy states

plastics do not melt like an ice cube, they rubberize



Characteristics of Plastics• Transparent or translucent• Chemical resistance• Thermal and electrical insulators• Low density• Varying strengths

Kevlar• Mold or extrude• Elasticity

regain original shape if quick stress applied• Foamed• Tend to soften when heated

rather than quickly melt



Synthetic PolymersPolyethylene

HDPELDPE

Polypropylene

Polyvinyl chloride

PolyamidesnylonKevlar

Polyesterspolyethylene terephthalate



1

Polyethylene Terephthalate (PET)

• Condensation copolymer of ethylene glycol + terephthalic acidA polyester

• Transparent

• High-impact strength

• Nonreactive with acid and atmospheric gases

• Doesn’t stretch

• Used for soda bottles, Dacron, Mylar



2

High Density Polyethylene (HDPE)• Addition polymer with linear chains• Opaque• Denser than LDPE• Mechanically stronger than LDPE• More rigid than LDPE

more crystalline• Higher heat resistance than LDPE• Nonreactive to acids and bases• Absorbs oils and softens• Oxidizes on exposure to air and sunlight• Subject to cracking• Used for containers, caps, bullet-proof vests,

synthetic ice173Tro: Chemistry: A Molecular Approach, 2/e


3

Poly Vinyl Chloride (PVC)

• Addition polymer• Transparent to opaque• Flame resistant• Low heat resistance• Good chemical resistance• High-impact strength• Quite rigid• Many additives used to modify properties

plasticizer adds flexibility• Used in food wrap, pipes, flooring and wall

covering, toys, hoses, auto trim, squeeze tubes, and appliance housings



4

Low Density Polyethylene (LDPE)

• Addition polymer with branched chains

• Lower density, strength, heat resistance (100–125 °C), and rigidity than HDPE

• Used in food, trash, and grocery bags as well as in electrical wire insulation



5

Polypropylene (PP)• Addition polymer

• Opaque

• High stretching strength

• High heat resistance (170 °C)

• Excellent chemical resistance

• Flexed almost indefinitely without tearing

• Smooth surface with high luster

• Used in carpets and upholstery; chemical resistant pipes, containers, and tanks; margarine tubs; and medicine bottles



6Polystyrene (PS)

• Addition polymer

• Low-impact resistance

• Fair strength and stiffness

• Poor chemical resistance

• Transparent, glassy, sparkling clarity

• Moderate heat resistance (90 °C)

• Used in model cars, computer housing, Styrofoam, clear drinking cups, and hard-molded parts



Acrylics

• Polymethylmethacrylate, PMMA• Low-impact resistance• Good strength and stiffness• Excellent transparency• Excellent scratch resistance• Moderate heat resistance• Addition polymer of methyl methacrylate• Uses include Plexiglas, Lucite, lighting fixtures,

lenses, fiber optic filament, appliance faceplates, decorative signs, and paints

• Also, reduces oil viscosity



Polycarbonates (PC)• Excellent physical properties

• Excellent toughness

• Very good heat resistance

• Fair chemical resistance

• Transparent

• Condensation copolymer of Bisphenol A and phosgene

• Lexan, Calibre , Makrolon , Panlite

• Used in equipment housings, exterior auto parts, outdoor light fixtures, non-auto vehicle windows, structural parts, medical supply parts, scratch-resistant coatings, eye wear, bullet-proof glass, and DVDs



Nylon• Condensation copolymer of a diamine with a diacid

polyamidesnylon 6,6

made by condensing 1,6–hexandiamine, H2N–(CH2)6–NH2, with hexandioic acid, HOOC–(CH2)4–COOH

• Good physical propertiesaffected by moisture

• Very good heat resistance• Excellent chemical resistance• Excellent wear resistance


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