1. Chapter 20 Organic Chemistry
Chemistry: A Molecular Approach, 2nd Ed. Nivaldo Tro
Chapter 20 Organic Chemistry
Roy Kennedy
Massachusetts Bay Community College
Wellesley Hills, MA
Copyright  2011 Pearson Education, Inc.

2. What Is Organic Chemistry?
Organic chemistry study of carbon containing compounds, their properties and their reactions
Organics can also contain hydrogen, nitrogen, oxygen, sulfur.
Organic compounds are found in all three states
solids tend to have low melting points
gases tend to be low molar mass
Life exists because of organic chemistry
Biochemistry is a closely related field
Organic molecules range from simple to very large and complex
It is this complexity that allows the complex functions of the cells to occur

3. Organic Compound’s Properties
Solubility in water varies depending on the
number of carbons
what other elements are attached to C and
how many of those other elements there are, e.g. , CH3OH is miscible with water, but C10H21OH is insoluble
Most common smells are caused by organic molecules
Odorants must be volatile (low molar mass), but not all volatile substances have a scent
Our sense of smell helps us identify food, people, and other organisms, and alerts us to dangers such as polluted air or spoiled food

4. Differences Between Organic and Inorganic Compounds
Organic compounds are easily decomposed into simpler substances by heating, but inorganic substances are not
Inorganic compounds are readily synthesized in the lab, but synthesis of organic compounds in the lab is more difficult
carbon monoxide, carbon dioxide, carbonates, and carbides are not organic compounds

5. Bond Energies and Reactivities
Carbon-carbon bonds are very strong and non-reactive

6. Carbon Bonding
There are millions of different organic compounds because carbon can form single, double, or triple bonds
Carbon with four bonds is tetrahedral (sp3 hybridized)
Carbon with three bonds (one double and two single bonds) is trigonal planar (sp2 hybridized)
Carbon with two bonds (one triple and one single, or two double bonds) is linear (sp hybridized)

7. Hydrocarbons Hydrocarbons contain only C and H (nonpolar molecules)
Molecules held together by London dispersion forces
insoluble in water
Less dense than water
BP and MP increases with molecular size
Aliphatic hydrocarbons
saturated = alkanes,
unsaturated = alkenes or alkynes
carbon atoms can attach together in long chains, or they can attach together to form rings
Aromatic hydrocarbons

8. Saturated Hydrocarbons
Saturated (with hydrogens) hydrocarbons only have C─C single bonds, sp3 hybridization, are called alkanes
Straight chain alkanes, also called normal alkanes, have the general formula CnH2n+2
Ring alkanes have 2 fewer hydrogens per ring formed and have the general formula CnH2n
Unsaturated Hydrocarbons
Unsaturated hydrocarbons have one or more carbon-carbon double (alkenes, general formula CnH2n) or triple bonds (alkynes, general formula CnH2n-2)
remove two H for each double bond
remove four H for each triple bond

9. Aromatic Hydrocarbons
Aromatic hydrocarbons contain a ring structure that seems to have double bonds, but the compound has enhanced stability vs. alkenes
The most prevalent and simplest example is benzene (C6H6)
CnHn
CnH2n+2
CnH2n-2
CnH2n

10. Uses of Hydrocarbons

11. 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 CnH2n
Alkane CnH2n+2
Alkyne CnH2n-2

12. Formulas
Molecular formulas tell you the type and number of atoms in a molecule, but not how they are attached
Structural formulas show you the attachment pattern
In addition, models show you the shape of the molecule
The condensed formula lists each central atom and then gives the attached groups directly after
Parentheses are used to indicate more than one group attached to same previous central atom

13. Structural formula for the n-Alkane C8H18
Connect the C atoms in a row
Carbon backbone =
Add H to give four bonds on each C.
middle C gets 2 H’s
end C gets 3 H’s
The condensed formula has the H attached to each C written directly after it. The bonds between carbons are not shown
Condensed formula for the n-Alkane C8H18

14. Draw a complete structural formula for CH2CHCH2CH(CH3)CH2CH3
after the entire chain is constructed, apply the rule 4 bonds per C to identify double or triple bonds
continue adding each successive C with its attached H’s or branch chains
start by writing the first C with its attached H’s

15. Write a complete structural formula for the straight chain isomer of C7H16

16. Draw a complete structural formula for CHCCH2C(CH3)2CH3

17. Carbon Skeleton Formulas
Only lines drawn, C atoms indicated by a line intersection or a line end
H on carbon is omitted from the structure
But included on functional groups
Multiple bonds are indicated

18. Draw a complete structural formula for each of the following

19. Isomers: Different Molecules Having the Same Molecular Formula, e. g
Isomers: Different Molecules Having the Same Molecular Formula, e.g. C4H10
Structural isomers have same number and type of atoms, but different atom attachments
Structural isomers have different properties
Butane, BP = 0 °C
Isobutane, BP = −12 °C

20. Rotation about a Bond Is NOT Isomerism
Stereoisomers are isomers with the same pattern of atom attachments, but the atoms have a different spatial orientation

21. Possible Structural Isomers

22. 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

23. Example 20.1: Write the structural formula and carbon skeleton formula for the 5 structural isomers of C6H14
fill in the H to give each carbon four bonds

24. 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
n-hexane
BP 69 ºC
2-methylpentane
BP 60 ºC
3-methylpentane
BP 63 ºC
2,2-dimethylbutane
BP 50 ºC
2,3-dimethylbutane
BP 58 ºC

25. Draw the three structural isomers of pentane

26. Alkane MP and BP
Ring alkanes have higher boiling points than straight chain alkanes (not shown)
Branched chain alkanes have lower boiling points than straight chain alkanes

27. Naming Alkanes/Alkenes & Alkynes
a “parent”, which indicates the length of the longest carbon chain or # of carbons in a ring
Each name consists of a “prefix”, which indicates position, number, and type of branches and/or functional groups
a “suffix”, which indicates the type of hydrocarbon, ane (saturated), ene (unsaturated with double bond), yne (unsaturated with triple bond) and/or the presence of certain functional groups

28. Naming Alkanes 1. Find the longest continuous carbon chain
2. Number the chain from end closest to a branch
if the first branches are equi-distant use next one 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 prefixes such as 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

29. Alkyl Groups

30. Example – Name the alkane
1. Find the longest continuous C chain and use it to determine the base name
because the longest chain has 5 C
the base name is pent- and since this is a saturated hydrocarbon, it has an –ane ending, pentane

31. Example – Name the alkane
2. Identify the substituent branches
there are 2 substituents
both are 1 C chains, called methyl

32. Example – Name the alkane
Number the chain and substituents
determine the end closest to a substituent branch
if first substituent is equi-distant from start as the last one is from the end, refer 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 equi-distant from the end, no other groups to reference

33. Example – Name the alkane
4. Write the name in the following order
substituent number of first alphabetical substituent followed by dash
If two of the same group, their numbers are separated by a comma, then followed by the dash
b) substituent name for first alphabetical substituents only, followed by a dash
no dash for last substituent listed
use prefixes to indicate multiple identical substituents
c) repeat for other substituents alphabetically
d) finally, name of main chain
2,4 –
dimethyl
pentane

34. Examples of Naming Alkanes
3-ethyl-2-methylpentane

35. Draw and name all nine structural isomers of heptane

36. Draw and name all nine structural isomers of heptane
Start by drawing the carbon skeleton of the straight chain isomer
The prefix hept- means 7, so the molecular formula is C7H16
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

37. Draw and name all nine structural isomers of heptane
Take a two C chain off the right end of the parent straight chain and attach it to the third C in from the left end (putting it on the second carbon gives a previously identified structure)
Then keep moving it down the chain, but not beyond halfway
Take another C off the right end of 2,2-dimethyl isomer and attach it to the third C in from the left end
Then keep moving it down the chain (not possible here)
Now reposition that second C substituent to be on the same carbon as the first substituent
Then keep moving it down the chain
Take another C off the right end of 2-methyl isomer and attach it to the third C in from the left end
Then keep moving it down the chain

38. Draw & name all 9 structural isomers of heptane
Find the base name of each main chain
Number the main chain from end closest to a substituent
Name and number the alkyl groups
n-Heptane
n-heptane
Hexanes
2-methylhexane
3-methylhexane
2,2-dimethylpentane
Pentanes
2,3-dimethylpentane
2,4-dimethylpentane
3,3-dimethylpentane
Butane
2,2,3-trimethylbutane
3-ethylpentane

39. Alkenes: Aliphatic Unsaturated Hydrocarbons
Also known as olefins (C=C double bonds)
Formula CnH2n (for 1 C=C)
subtract 2 H for each additional double bond
Trigonal planar shape around carbon, sp2
Polyunsaturated = many double bonds
No free rotation around double bond
Composed of 1sigma (s) and 1 pi (p) bond
Not twice as strong as single bond, therefore less stable and more reactive
Shorter than single bond, longer than triple bond

40. Physical Properties of Alkenes
pi electrons not held as tight as sigma, therefore alkenes are more polarizable than alkanes
cis isomer generally more polar than trans
trans lower boiling point than cis
trans higher melting point than cis
molecules are more symmetrical and pack better
densities similar to alkanes

41. produced by ripening fruit
used to make polyethylene
used to make polypropylene

42. Alkynes Aliphatic, unsaturated, CºC triple bond
sp hybridized, linear shape
Formula for one triple bond = CnH2n−2
subtract 4 H from alkane for each triple bond
Internal alkynes have both triple bond carbons attached to C
Terminal alkynes have one carbon attached to H
Composed of 2 pi bonds and 1 sigma
Shorter than C–C and C=C
Stronger than C–C, but not 3x as strong
CºC = 836 kJ/mol, C–C = 368 kJ/mol

43. Physical Properties of Alkynes
Higher boiling points than similar sized alkenes
similar size = same number of carbons
more 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 alkynes
with the same number of C

44. aka acetylene

45. 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

46. Examples of Naming Alkenes
Examples of Naming Alkynes
4-methyl-2-pentyne 46

47. Name the Alkene
1. 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 has
6 C the base name is hexene

48. Name the Alkene 2. Identify the substituent branches
there are 2 substituents
one is a 1 C chain, called methyl
the other one is a 2 C chain, called ethyl

49. Name the Alkene 3. number the chain and substituents
a) determine the end closest to the double bond
if double bond equi-distant from both ends, number from end closest to the substituents
Find the longest parent chain
….much better
….oops, try again
b) then assign numbers to each substituent based on the number of the main chain C it is attached to
4-methyl
3-ethyl

50. Name the Alkene 4. Write the name in the following order 3–ethyl–
a. substituent number of first alphabetical substituent – substituent name of second alphabetical substituent –
use prefixes di, tri, tetra to indicate multiple identical substituents
b. repeat step a. for other substituents
c. – number of first C in double bond – name of main chain with ene ending
3–ethyl–
4–methyl–
2–hexene
3-ethyl
4-methyl 1 2 3 4 5 6
2-ene
hex

51. Name the following 3,4-dimethyl-3-hexene5 6 2 1
3,4-dimethyl-3-hexene
Did you notice that this is a C C
symmetrical molecule? | |
C-C-C-C-C-C

52. Name the Alkyne
1. 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

53. Name the Alkyne 2. Identify the substituent branches
there are 2 substituents
one is a 1 C chain, called methyl
the other one is called isopropyl

54. Name the Alkyne 3. number the chain and substituents
determine the end closest to the triple bond
if triple bond equidistant from both ends, number from end closest to the substituents
then assign numbers to each substituent based on the number of the main chain C it is attached to 1 2 3 4 5 6 7 4 6

55. Name the Alkyne 4. write the name in the following order 4–isopropyl–
a) substituent number of first alphabetical substituent – substituent name of first alphabetical substituent –
use prefixes to indicate multiple identical substituents
b) repeat for other substituents
c) number of first C in triple bond – name of main chain 1 2 3 4 5 6 7 4 6
4–isopropyl–
6–methyl–
2–heptyne

56. Name the Following 3 2 1 4 5
3,3-dimethyl-1-pentyne

57. Stereoisomers
Stereoisomers are two different molecules whose atoms are connected in the same order, but with a different spatial orientation. They can be geometric or optical isomers
Geometric isomers are stereoisomers that are not optical isomers
Because the rotation around a double bond is highly restricted, you will have different molecules if groups are on the same side of the double bond, cis , vs. when the groups are on opposite sides of the double bond, trans
called cis–trans isomerism

58. There is Free Rotation Around C─C
But No Free Rotation for C=C: Cis-Trans Isomerism

59. Cis-Trans Isomerism
The cis and trans isomers are different molecules with different properties.

60. Cis–Trans Isomerism is important in nature

61. Optical Isomers are Non-superimposable Mirror Images
A pair of non-superimposable mirror images is called a pair of enantiomers
Any molecule with a non-superimposable mirror image is said to be chiral
Any carbon with 4 different substituents will be a chiral center
a mirror image cannot be rotated so all its atoms align with the same atoms of the original molecule

62. Optical Isomers of 3-methylhexane

63. Draw the mirror image of the molecule and decide if they are enantiomers

64. Optical Activity
Plane-polarized light is filtered so that only the waves traveling in a single plane are allowed through
Enantiomer’s physical properties are identicle, except the direction they rotate plane-polarized light
Each enantiomer will rotate the light plane the same amount, but in opposite directions
dextrorotatory = rotates the plane to the right
levorotatory = rotates the plane to the left

65. Mixtures of Enantiomers
An equimolar mixture of a pair of enantiomers is called a racemic mixture
Half the molecules rotate plane polarized light to the left and the other half rotates it to the right
the rotations cancel, so the racemic mixture does not rotate the light plane
Assuming a pure enantiomer’s rotation is known, a non-racemic mixture can be analyzed by the percent rotation vs. the pure enantiomer’s rotation
A pair of enantiomers will have the same chemical reactivity in a non-chiral environment, but in a chiral environment they may exhibit different behaviors
enzymes select only one enantiomer of a pair
this behavior is called shape selectivity

66. Reactions of Hydrocarbons
All hydrocarbons can be combusted
Combustion is exothermic, releases heat & light energy
about 90% of U.S. energy generated by combustion
The larger the alkane, the more heat is released
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 CH3CCCH3(g) + 11 O2(g) → 8 CO2(g) + 6 H2O(g)

67. Alkane Substitution Reactions
replace H with a halogen atom
initiated by addition of energy in the form of heat or ultraviolet light to start breaking bonds
get multiple products with multiple substitutions

68. Addition Reactions of Alkenes and Alkynes: adding a molecule across the multiple bond
Adding H2 (Hydrogenation) converts unsaturated molecule to saturated (generally requires a catalyst)
alkene + H2 → alkane OR alkyne + H2 → alkene + H2 → alkane
Adding X2 (Halogenation)
Adding HX (Hydrohalogenation)
when adding a polar reagent, such as HX, to a double or triple bond, the positive part attaches to the carbon with the most H’s

69. Resonance Hybrid Aromatics contain benzene ring structure
Though drawn with localized C=C, they do not behave like alkenes
The true structure of benzene is a resonance hybrid of two structures

70. Naming Monosubstituted Benzenes
“Substituent name”benzene
halogen substituent = change ending to “o”
Alkane group = change ending to “yl”
but some have common names
hydroxybenzene
methylbenzene
aminobenzene
phenylethylene
When the benzene ring is not the parent, but a substituent, it is called a phenyl group

71. Naming Disubstituted Benzenes
Number the ring starting at attachment for first alphabetical substituent, then move toward second
use “di” if both substituents are the same
Alternatively, use relative position prefix
ortho- = 1,2; meta- = 1,3; para- = 1,4
2-chlorotoluene
ortho-chlorotoluene
o-chlorotoluene
3-chlorotoluene
meta-chlorotoluene
m-chlorotoluene
4-chlorotoluene
para-chlorotoluene
p-chlorotoluene

72. 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 have a characteristic influence on the properties of the molecule
generally, the reactions that a compound will perform are determined by what functional groups it has
because the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol R
CH3—OH
R group
functional group

73. Alcohols R—OH Main chain must contain OH
Methanol = CH3OH = wood alcohol from thermolysis of wood
Poisonous
Used in paint solvent
Ethanol = CH3CH2OH = grain alcohol = fermentation of sugars in grains
Alcoholic beverages (proof number = 2 x % of alcohol)
Gas additive
Isopropyl alcohol = (CH3)2CHOH = rubbing alcohol = 2-propanol
Main chain must contain OH
Number main chain from end closest to OH
Add ol ending to the base name
Use number of C where OH attached in front of name
Name as hydroxy group if higher precedence group present

74. Naming Alcohols 4-ethyl-4-methyl-3-hex-5-enol 1 2 3 4 5 6 1 2 3 5 4 3
3-ethyl-1-hexanol
1-pent-4ynol

75. Reactions of Alcohols Nucleophilic substitution
CH3─OH HCl ® CH3Cl + H2O
Acid catalyzed elimination (dehydration)
CH3─ CH2OH ® CH2═CH H2O
H2SO4
Oxidation
CH3CH2OH ® CH3CHO ® CH3COOH
−2 H
a common oxidizing agent is Na2Cr2O7
Alcohols with very active metals
2 CH3─OH K ® 2 CH3O−K H2

76. Aldehydes and Ketones Contain the carbonyl group (C=O)
Aldehydes = at least 1 H on C
Ketones = C has two R groups
Formaldehyde = H2C=O
pungent gas
formalin = a preservative
wood smoke, carcinogenic
Acetone = CH3C(=O)CH3
nail-polish remover
Many aldehydes and ketones have pleasant tastes and aromas
Some are pheromones

77. Aldehyde Odors and Flavors
butanal = butter
vanillin = vanilla
benzaldehyde = almonds
cinnamaldehyde = cinnamon

78. Ketone Odors and Flavors
acetophenone = pistachio
carvone = spearmint
ionone = raspberries
muscone = musk

79. Naming Aldehydes and Ketones
Main chain must contain C=O
unless COOH present
Number main chain from end closest to C=O
For aldehydes, give base name an “al” ending
always on C1
For ketones, give base name an “one” ending and start numbering from the end closest to the C=O 5 4 3 2 1 2 4 5 6 1 3
4-methyl-3-hexenal
5-hydroxy-3-isopropyl-4-methyl-2-hexanone 79

80. 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

81. C=O group is highly polar many reactions involve addition across C=O,
Addition to C=O
polar molecules add across the C=O, with the positive part attaching to O
C=O group is highly polar many reactions involve addition across C=O,
with positive part attached to O d+ d−

82. Carboxylic Acids - RCOOH
Sour tasting
Weak acids
Citric acid
found in citrus fruit
Ethanoic acid = acetic acid
vinegar
Methanoic acid = formic acid
insect bites and stings

83. Naming Carboxylic Acids
Carboxylic acid group always on end of main chain
has highest naming precedence of functional groups
always C1, therefore, position not indicated in name
Change ending to oic acid

84. Synthesis of Carboxylic Acids
Made by the oxidation of aldehydes and alcohols

85. RaCOOH + RbOH  RaCOORb + H2O
Esters = R–COO–R
Made by reacting carboxylic acid with an alcohol
RaCOOH + RbOH  RaCOORb + H2O
Sweet odor

86. Naming Esters Begin name with alkyl substituent attached to ester O
Carboxylic acid ester group always on end of main chain
unless carboxylic acid group present
ester group always on C1, so position not indicated in name
Begin name with alkyl substituent attached to ester O
Name main chain with oate ending

87. Condensation Reactions
A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water
Synthesis of Aspirin (Acetylsalicylic Acid)
Esters are made by the condensation reaction between a carboxylic acid and an alcohol
the reaction is acid catalyzed
Acid anhydrides are made by the condensation reaction between 2 carboxylic acid molecules
the reaction is driven by heat

88. Ethers = R–O–R Ether = diethyl ether = CH3CH2OCH2CH3
Anesthetic
Polar molecules
Used as solvents
To name ethers, name each alkyl group attached to O, then add the word ether to the end
isopropyl methyl ether

89. Amines N containing organic molecules
Very bad smelling
Organic bases
Form when proteins decompose
Name alkyl groups attached to the N, then add the word amine to the end
isopropyl methyl amine

90. Amines Many amines are biologically active
dopamine – a neurotransmitter
epinephrine – an adrenal hormone
pyridoxine – vitamin B6
Alkaloids are plant products that are alkaline and biologically active
toxic
coniine from hemlock
cocaine from coca leaves
nicotine from tobacco leaves
mescaline from peyote cactus
morphine from opium poppies

91. RCOOH + H—NHR’  RCONHR’ + H2O
Amine Reactions
Weak bases
react 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

92. Polymers

93. 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

94. 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

95. 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

96. 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 polymerization
head-to-tail most common
regular pattern gives stronger attractions between chains than random arrangements

98. Addition Polymerization
Monomers add to the growing chain in such a manner that all the atoms in the original monomer wind up in the chain
no other side products formed, no atoms eliminated
First monomer must “open” to start reaction
done with heat, or the addition of an initiator
The process is a chain reaction
each added unit ready to add another

99. Addition Polymerization of Vinyl Chloride

100. Condensation Polymerization
Monomer units are joined by removing small molecules from the combining units
polyesters, 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

101. Condensation Polymerization

102. 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 state
solid that has semi-fluid characteristics
glass transition temperature is where an amorphous polymer is converted between rubbery and glassy states
plastics do not melt like an ice cube, they rubberize

103. 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

104. Synthetic Polymers Polyethylene – HDPE & LDPE Polypropylene
Polyvinyl chloride
Polyesters
polyethylene terephthalate
Polyamides
nylon
Kevlar

105. Polyethylene Terephthalate (PET)
Condensation copolymer of ethylene glycol + terephthalic acid
A polyester
Transparent
High-impact strength
Nonreactive with acid and atmospheric gases
Doesn’t stretch
Used for soda bottles, Dacron, Mylar 1

106. High Density Polyethylene (HDPE)2
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 ice

107. Poly Vinyl Chloride (PVC)3
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

108. 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 4

109. Polypropylene (PP) Addition polymer Opaque 5 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

110. Polystyrene (PS) 6 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

111. 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

112. 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

113. Nylon Condensation copolymer of a diamine with a diacid
polyamides
nylon 6,6
made by condensing 1,6–hexandiamine, H2N–(CH2)6–NH2, with hexandioic acid, HOOC–(CH2)4–COOH
Good physical properties
affected by moisture
Very good heat resistance
Excellent chemical resistance
Excellent wear resistance