Chapter 20 Organic Chemistry

1
Chapter 20OrganicChemistry
Chemistry A Molecular Approach, 1st Ed.Nivaldo
Tro
Roy Kennedy Massachusetts Bay Community
College Wellesley Hills, MA
2008, Prentice Hall
2
Overview
3
Structure Determines Properties

• Organic compounds all contain carbon
• CO, CO2 , carbonates and carbides are inorganic
• other common elements are H, O, N, (P, S)
• Carbon has versatile bonding patterns
• chains, rings, multiple bonds
• chain length nearly limitless
• Carbon compounds generally covalent
• molecular gases, liquids, or low melting solids
  varying solubilities nonconductive in liquid
• C - C bonds unreactive (very stable)

4
Overview

• Carbon uses sp3, sp2, and sp hybridization in
  forming the four bonds per carbon atom common to
  almost all carbon compounds.
• With sp hybridization, there are two (2) p bonds
  and 2 s bonds.
• With sp2 hybridization there is one (1) p bond
  and 3 s bonds.

5
Why Carbon
sp3, sp2, and sp hybridization
6
FUNCTIONAL GROUPS

• Alkane
• Alkene
• Alkyne
• Alkyl halide
• Aromatic
• Alcohol
• Aldehyde
• Ketone
• Carboxylic Acid
• Ester
• Amine
• Amide

Organic chemistry is the study of compounds
containing carbon. The goal of studying Organic
chemistry is the making of carbon-carbon bonds,
C-X, C-O, C-N, and C-S bonds to make new molecules
Inorganic molecules like CO, and CO3-2 are not
considered organic molecules.
7
Bond Energies and Reactivities
8
Allotropes of Carbon - Diamond
9
Allotropes of Carbon - Graphite
10
Carbon Bonding

• mainly forms covalent bonds
• C is most stable when it has 4 single covalent
  bonds, but does form double and triple bonds
• CC and CC are more reactive than C-C
• C with 4 single bonds is tetrahedral,
• 2 singles and 1 double is trigonal planar
• 2 doubles or 1 triple and 1 single is linear

11
Hydrocarbons

• hydrocarbons contain only C and H
• aliphatic or aromatic
• insoluble in water
• no polar bonds to attract water molecules
• aliphatic hydrocarbons
• saturated or unsaturated aliphatics
• saturated alkanes, unsaturated alkenes or
  alkynes
• may be chains or rings
• chains may be straight or branched
• aromatic hydrocarbons

12
Uses of Hydrocarbons
13
Saturated Hydrocarbons

• a saturated hydrocarbon has all C-C single bonds
• it is saturated with hydrogens
• saturated aliphatic hydrocarbons are called
  alkanes
• chain alkanes have the general formula CnH2n2

14
Unsaturated Hydrocarbons

• unsaturated hydrocarbons have one of more CC
  double bonds or C?C triple bonds
• unsaturated aliphatic hydrocarbons that contain
  CC are called alkenes
• the general formula of a monounsaturated chain
  alkene is CnH2n
• remove 2 more H for each additional unsaturation
• unsaturated aliphatic hydrocarbons that contain
  C?C are called alkynes
• the general formula of a monounsaturated chain
  alkyne is CnH2n-2
• remove 4 more H for each additional unsaturation

15
Unsaturated Hydrocarbons
16
Aromatic Hydrocarbons

• contain benzene ring structure
• even though they are often drawn with CC, they
  do not behave like alkenes

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19
Formulas

• molecular formulas just tell you what kinds of
  atoms are in the molecule, but they dont 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

20
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 1 identical group
  attached to same previous central atom
• unless () group listed first in which case
  attached to next central atom

21
Line-Angle Formulas

• each angle, and beginning and end represent a C
  atom
• H omitted on C
• included on functional groups
• multiple bonds indicated
• double line is double bond, triple line is triple
  bond

22
Formulas
23
Formulas
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Isomerism

• Isomers different molecules with the same
  molecular formula
• Structural Isomers different pattern of atom
  attachment
• Constitutional Isomers
• Stereoisomers same atom attachments, different
  spatial orientation

26
Structural Isomers of C4H10
Butane, BP 0C
Isobutane, BP -12C
27
Rotation about a bond is not isomerism
28
Possible Structural Isomers
29
Ex 20.1 Write the structural formula and carbon
skeleton formula for C6H14
30
Ex 20.1 Write the structural formula and carbon
skeleton formula for C6H14
31
Ex 20.1 Write the structural formula and carbon
skeleton formula for C6H14
32
Stereoisomers

• stereoisomers are different molecules whose atoms
  are connected in the same order, but have a
  different spatial direction
• optical isomers are molecules that are
  nonsuperimposable mirror images of each other
• geometric isomers are stereoisomers that are not
  optical isomers

33
Nonsuperimposable Mirror Images
mirror image cannot be rotated so all its atoms
align with the same atoms of the original
molecule
34
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

35
Optical Isomers of 3-methylhexane
36
Plane Polarized Light

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

37
Optical Activity

• a pair of enantiomers have all the same physical
  properties except one the direction they rotate
  the plane of plane polarized light
• each will rotate the plane the same amount, but
  in opposite directions
• dextrorotatory rotate to the right
• levorotatory rotate to the left
• an equimolar mixture of the pair is called a
  racemic mixture
• rotations cancel, so no net rotation

38
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 behaviors
• enzyme selection of one enantiomer of a pair

39
Alkanes

• aka paraffins
• aliphatic
• general formula CnH2n2 for chains
• very unreactive
• come in chains or/and rings
• CH3 groups at ends of chains, CH2 groups in the
  middle
• chains may be straight or branched
• saturated
• branched or unbranched

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Naming

• each name consists of 3 parts
• prefix
• indicates position, number, and type of branches
• indicates position, number, and type of each
  functional group
• parent
• indicates the length of the longest carbon chain
  or ring
• suffix
• indicates the type of hydrocarbon
• ane, ene, yne
• certain functional groups

42
Naming Alkanes

• Find the longest continuous carbon chain
• Number the chain from end closest to a branch
• if first branches equal distance use next in
• Name branches as alkyl groups
• locate each branch by preceding its name with the
  carbon number on the chain
• List branches alphabetically
• do not count n-, sec-, t-, count iso
• Use prefix if more than one of same group present
• di, tri, tetra, penta, hexa
• do not count in alphabetizing

43
Alkyl Groups
44
More Alkyl Groups
45
Examples of Naming Alkanes
2-methylpentane
3-isopropyl-2,2-dimethylhexane
46
Example Name the alkane

• find the longest continuous C chain and use it to
  determine the base name

since the longest chain has 5 C the base name is
pentane
47
Example Name the alkane

• identify the substituent branches

there are 2 substituents both are 1 C chains,
called methyl
48
Example Name the alkane

• number the chain from the end closest to a
  substituent branch
• if first substituents equidistant from end, go to
  next substituent in

then assign numbers to each substituent based on
the number of the main chain C its attached to
1 2 3 4 5
both substituents are equidistant from the end
2 4
49
Example Name the alkane

• write the name in the following order
• substituent number of first alphabetical
  substituent followed by dash
• substituent name of first alphabetical
  substituent followed by dash
• if its the last substituent listed, no dash
• use prefixes to indicate multiple identical
  substituents
• repeat for other substituents alphabetically
• name of main chain

2,4
dimethyl
pentane
2 4
50
Practice Name the Following
51
Practice Name the Following
3-ethyl-2-methylpentane
52
Drawing Structural Formulas
4-ethyl-2-methylhexane

• draw and number the base chain carbon skeleton
• add the carbon skeletons of each substituent on
  the appropriate main chain C
• add in required Hs

53
Practice Draw the structural formula of
4-isopropyl-2-methylheptane
54
Practice Draw the structural formula of
4-isopropyl-2-methylheptane
55
Alkenes

• also known as olefins
• aliphatic, unsaturated (more later)
• CC double bonds
• formula for one double bond CnH2n
• subtract 2 H from alkane for each double bond
• trigonal shape around C
• flat
• much more reactive than alkanes
• polyunsaturated many double bonds

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Alkenes
ethene ethylene
propene
58
Physical Properties of Alkenes
59
Alkynes

• also known as acetylenes
• aliphatic, unsaturated (more in just a minute)
• CºC triple bond
• formula for one triple bond CnH2n-2
• subtract 4 H from alkane for each triple bond
• linear shape
• more reactive than alkenes

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Alkynes
ethyne acetylene
propyne
62
Physical Properties of Alkynes
63
Saturated Hydrocarbon C15H32
Saturated vs- Unsaturated
64
Unsaturated Hydrocarbon
Contains either double and/or triple bonds
Notice how the chains do not line up
65
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

66
Examples of Naming Alkenes
2-methyl-1-pentene
3-isopropyl-2,2-dimethyl-3-hexene
67
Examples of Naming Alkynes
3-methyl-1-pentyne
4-isopropyl-5,5-dimethyl-2-hexyne
68
Name the Alkene

• find the longest, continuous C chain that
  contains the double bond and use it to determine
  the base name

since the longest chain with the double bond has
6 C the base name is hexene
69
Name the Alkene

• 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
70
Name the Alkene

• number the chain from the end closest to the
  double bond

then assign numbers to each substituent based on
the number of the main chain C its attached to
71
Name the Alkene

• write the name in the following order
• substituent number of first alphabetical
  substituent substituent name of first
  alphabetical substituent
• use prefixes to indicate multiple identical
  substituents
• repeat for other substituents
• number of first C in double bond name of main
  chain

3ethyl
4methyl
2hexene
72
Practice Name the Following
73
Practice Name the Following
3
4
5
6
1
2
3,4-dimethyl-3-hexene
74
Name the Alkyne

• find the longest, continuous C chain that
  contains the triple bond and use it to determine
  the base name

since the longest chain with the triple bond has
7 C the base name is heptyne
75
Name the Alkyne

• identify the substituent branches

there are 2 substituents one is a 1 C chain,
called methyl the other one is called isopropyl
76
Name the Alkyne

• number the chain from the end closest to the
  triple bond

then assign numbers to each substituent based on
the number of the main chain C its attached to
77
Name the Alkyne

• write the name in the following order
• substituent number of first alphabetical
  substituent substituent name of first
  alphabetical substituent
• use prefixes to indicate multiple identical
  substituents
• repeat for other substituents
• number of first C in double bond name of main
  chain

4isopropyl
6methyl
2heptyne
78
Practice Name the Following
79
Practice Name the Following
1
2
3
4
5
3,3-dimethyl-1-pentyne
80
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 bond
• this is often called cis-trans isomerism
• when groups on the doubly bonded carbons are cis,
  they are on the same side
• when groups on the doubly bonded carbons are
  trans, they are on opposite sides

81
Free Rotation AroundC-C
82
Cis-Trans Isomerism
83
Reactions of Hydrocarbons

• all hydrocarbons undergo combustion
• combustion is always exothermic
• about 90 of U.S. energy generated by combustion
• 2 CH3CH2CH2CH3(g) 13 O2(g) ? 8 CO2(g) 10
  H2O(g)
• CH3CHCHCH3(g) 6 O2(g) ? 4 CO2(g) 4 H2O(g)
• 2 CH3C?CCH3(g) 11 O2(g) ? 8 CO2(g) 6 H2O(g)

84
Other Alkane Reactions

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

85
Other Alkene and Alkyne Reactions

• Addition reactions
• adding a molecule across the multiple bond
• Hydrogenation adding H2
• converts unsaturated molecule to saturated
• alkene or alkyne H2 ? alkane
• Halogenation adding X2
• Hydrohalogenation adding HX
• HX is polar
• when adding a polar reagent to a double or triple
  bond, the positive part attaches to the carbon
  with the most Hs

86
Addition Reactions
This is called a Markovnikov Addition
87
Markovnikov Addition
The hydrogen adds to the carbon with the most
hydrogen
88
Preparation of Alkenes and Alkynes

• Acetylene aka ethyne, from calcium carbide, CaC2
  
• Steam cracking for the formation of ethylene,
  ethene, from ethane.
• Addition Reactions
• Symmetrical addition is simple, but asymmetrical
  addition follows Markovnikov's rule. The
  hydrogen adds to the carbon with the most
  hydrogen.
• For alkynes, the addition is always two mole to
  one mole of alkyne, the product being a
  substituted alkane. If hydrogen gas is added,
  the process is called hydrogenation.

89
Aromatic Hydrocarbons

• contain benzene ring structure
• even though they are often drawn with CC, they
  do not behave like alkenes

90
Resonance Hybrid

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

91
Naming Monosubstituted Benzene Derivatives

• (name of substituent)benzene
• halogen substituent change ending to o

• or name of a common derivative

92
Naming Benzene as a Substituent

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

93
Naming Disubstituted Benzene Derivatives

• number the ring starting at attachment for first
  substituent, then move toward second
• order substituents alphabetically
• use di if both substituents the same

94
Naming Disubstituted Benzene Derivatives

• alternatively, use relative position prefix
• ortho- 1,2 meta- 1,3 para- 1,4

2-chlorotoluene ortho-chlorotoluene o-chlorotoluen
e
3-chlorotoluene meta-chlorotoluene m-chlorotoluene
4-chlorotoluene para-chlorotoluene p-chlorotoluene
95
Practice Name the Following
96
Practice Name the Following
1-chloro-4-fluorobenzene
1,3-dibromobenzene or meta-dibromobenzene or
m-dibromobenzene
97
Polycyclic Aromatic Hydrocarbons

• contain multiple benzene rings fused together
• fusing sharing a common bond

98
Reactions of Aromatic Hydrocarbons

• most commonly, aromatic hydrocarbons undergo
  substitution reactions replacing H with another
  atom or group

99
halogenation
B
r


B
r


H
B
r
2
100
nitration
N
O
2
H
S
O

(
c
o
n
c
)
2
4



H
N
O

(
c
o
n
c
)


H
O
3
3
101
alkylation
C
H
C
H
C
H
C
H
2
2
2
3
C
H
C
H
C
H
C
H
C
l
3
2
2
2
A
l
C
l
3
102
Substitution reaction Overview
103
Substitution reaction Overview
104
Substitution reaction Overview
105
Substitution reaction Overview
106
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 molecule
• generally, the reactions that a compound will
  perform are determined by what functional groups
  it has
• since the kind of hydrocarbon chain is irrelevant
  to the reactions, it may be indicated by the
  general symbol R

CH3OH
R group
functional group
107
Nomenclature
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109
Draw the following

• dibutyl ether
• butanoic acid
• ethyl butanoate
• butyl amine
• dibutyl amine
• tributyl amine

• butane
• butene
• butyne
• butanol
• butanal
• butanone

110
Alcohols

• R-OH
• ethanol CH3CH2OH
• grain alcohol fermentation of sugars
• alcoholic beverages
• proof number 2X percentage of alcohol
• gasohol
• isopropyl alcohol (CH3)2CHOH
• 2-propanol
• rubbing alcohol
• poisonous
• methanol CH3OH
• wood alcohol thermolysis of wood
• paint solvent
• poisonous

111
Primary, secondary, and tertiary alcohols
R
R
R
R
C
O
H
R
C
O
H
C
O
H
H
R
H
H
p
r
i
m
a
r
y

o
r

1

s
e
c
o
n
d
a
r
y

o
r

2

t
e
r
t
i
a
r
y

o
r

3

112
Formation of ALCOHOLS
H
P
O
3
4
H
C
C
H


H
O
C
H
C
H
O
H
2
2
2
3
2
113
Naming Alcohols

• main chain contain 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 other higher precedence
  group present

1
2
3
4
5
6
4-ethyl-4-methyl-5-hex-3-enol
114
Reactions of Alcohols
Nucleophilic Substitution
Acid Catalyzed Elimination (Dehydration)
Oxidation
with Reactive Metals
115
Reactions

• aldehydes and ketones are generally synthesized
  by the oxidation of alcohols
• therefore, reduction of an aldehyde or ketone
  results in an alcohol

116
Alcohols can be oxidized to carboxylic acids or
ketones1. primary alcohols to aldehydes or acids
O
P
C
C
C
C
H
C
H
O
H
3
2
H
H
C
3
-
P
C
C


C
r
O
C
l

N
H
3
Pryidinium chlorochromate
117
Alcohols can be oxidized to carboxylic acids or
ketones2. secondary alcohols to ketones
O
O
H
P
C
C
C
C
H
C
H
C
H
C
H
H
C
3
3
3
3
2
-
p
r
o
p
a
n
o
l
p
r
o
p
a
n
o
n
e
118
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 H2CO
• pungent gas
• formalin a preservative
• wood smoke, carcinogenic
• acetone CH3C(O)CH3
• nail-polish remover

119
Aldehyde Odors and Flavors

• butanal butter
• vanillin vanilla
• benzaldehyde almonds
• cinnamaldehyde cinnamon

120
Ketone Odors and Flavors

• acetophenone pistachio
• carvone spearmint
• ionone raspberries
• muscone musk

121
Carbonyl Group
CO group is highly polar many reactions involve
addition across CO, with positive part attached
to O
122
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

123
Carboxylic Acids

• made by the oxidation of aldehydes and alcohols
• OH on the end of the chain
• always on main chain
• has highest precedence
• C of group always C1
• position not indicated in name
• change ending to oic acid

124
Naming Carboxylic Acids
125
Esters

• RCOOR
• sweet odor
• made by reacting carboxylic acid with an alcohol
• RaCOOH RbOH ? RaCOORb H2O
• name alkyl group from alcohol, then acid name
  with oate ending
• precedence over carbonyls, but not carboxylic
  acid
• number from end with ester group

126
Naming Esters
127
Condensation Reactions

• a condensation reaction is any organic reaction
  driven by the removal of a small molecule, like
  water

128
Synthesis of Aspirin(Acetylsalicylic Acid)
129
Ethers

• R O R
• ether diethyl ether CH3CH2OCH2CH3
• anesthetic
• to name ethers, name each alkyl group attached to
  the O, then add the word ether to the end

diethyl ether
130
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

putrescine
ethylamine
ethylmethylamine
cadaverine
131
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

132
Amine Reactions

• weak bases
• react with strong acids to form ammonium salts
• RNH2 HCl ? RNH3Cl-
• react with carboxylic acids in a condensation
  reaction to form amides
• RCOOH HNHR ? RCONHR H2O

133
Macromolecules

• polymers are very large molecules made by
  repeated linking together of small molecules
• monomers
• natural
• modified natural polymers
• synthetic
• plastics, elastomers (rubber), fabrics, adhesives
• composites
• additives such as graphite, glass, metallic flakes

134
Natural Polymers

• polysaccharides
• cellulose (cotton)
• starch
• proteins
• nucleic acids (DNA)
• natural latex rubber, etc.
• shellac
• amber, lignin, pine rosin
• asphalt, tar

135
Modified Natural Polymers

• Cellulose Acetate
• Rayon
• film
• Vulcanized Rubber
• Gun Cotton
• Celluloid
• ping-pong balls
• Gutta Percha
• fill space for root canal
• Casein
• buttons, mouldings, adhesives

136
Polymerization

• the process of linking the monomer units together
• two processes are addition polymerization and
  condensation polymerization
• monomers may link head-to-tail, or head-to-head,
  or tail-to-tail
• head-to-tail most common
• regular pattern gives stronger attractions
  between chains than random arrangements

137
Head-to-Tail
Head
Tail
Head
Tail
Head-to-Head, Tail-to-Tail
Tail
Tail
Head
Head
138
SYNTHETIC POLYMERS

• Another classification system for polymers is
  based on their intended use
• - plastics - fibers
• Elastomers - coatings
• - adhesives
• Polymers can also be classified by the way they
  form, which is what well do next
• addition polymers
• condensation polymers

139
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 addition of an initiator
• chain reaction
• each added unit ready to add another

140
Addition Polymerization




141
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142
PETE (polyethylene terephthalate), HDPE
(high-density polyethylene), LDPE (low-density
polyethylene), PP (polypropylene), CLPE
(cross-linked polyethylene, V (vinyl) or PVC,
also RLDPE (resin mix, already recycled. The is
another way of identifying that polymer.
143
Polyethylene
C
H
C
H
C
H
C
H
2
2
2
2
n
Polypropylene
C
H
C
H
3
3
C
H
C
H
C
H
C
H
2
2
n
144
Figure 11.14
(a)
Polyethylene
144
145
Teflon
C
F
C
F
C
F
C
F
2
2
2
2
n
What would the following addition polymers look
like
O
C
l
C
O
C
H
C
H
3
C
H
2
C
H
C
H
2
C
H
f
o
r

P
V
C
C
H
2
m
e
t
h
y
l

m
e
t
h
a
c
r
y
l
a
t
e
s
t
r
y
e
n
e
f
o
r

L
u
c
i
t
e
,

P
l
e
x
i
g
l
a
s
s
f
o
r

s
t
y
r
o
f
o
a
m
146
What would the following addition polymers look
like
147
Condensation Polymerization

• monomer units are joined by removing small
  molecules from the combining units
• polyesters, polyamides lose water
• no initiator needed
• chain reaction
• each monomer has two reactive ends, so chain can
  grow in two directions

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Condensation Polymerization

H2O
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Nylon

• polyamides
• good physical properties
• affected by moisture
• very good heat resistance
• excellent chemical resistance
• excellent wear resistance
• nylon 6,6 made by condensing
  1,6hexandiamine, H2N(CH2)6NH2, with
  hexandioic acid,
  HOOC(CH2)4COOH

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Making Nylon 6,6
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Polyamide Chains can H-Bond
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