This document provides an overview of carbon compounds and organic chemistry. It begins by outlining nine learning objectives, such as explaining the hybridization of atomic orbitals and molecular geometries. Next, it defines key terms like hybridization, sigma bonds, and functional groups. It then discusses the valence bond theory and how hybridization of atomic orbitals leads to sp, sp2, and sp3 hybrid orbitals. Examples are given of molecules like methane, ethylene, and acetylene to illustrate different types of hybridization. The document also explains the special ability of carbon to form many compounds through catenation and various bonding configurations. Finally, it introduces hydrocarbons like alkanes, alkenes, alkynes

1. CARBON
COMPOUNDS
Prepared by: Mrs. Eden C. Sanchez

2. Learning Objectives
1. Use the Valence Bond Theory to explain
the hybridization of atomic orbitals and
bonding in covalent compounds.
2. Relate the molecular geometries and bond
angles to the hybridization of atomic
orbitals used in bonding.
2

3. Learning Objectives
3. Describe the formation of sigma bonds and
pi bonds.
4. Describe the bonding in ethane, ethene,
and ethyne and other covalent compounds
containing single, double, and triple bonds.
5. Discuss the special nature of carbon and
its ability to form compounds.
3

4. Learning Objectives
6. Describe hydrocarbons, its properties and
reactions.
7. Identify structural and geometric isomers.
8. Identify basic functional groups in organic
compounds.
9. Describe simple reactions of organic
compounds.
4

5. Keywords
a. Hybridization
b. sp3 hybrid orbitals
c. sp2 hybrid orbitals
d. sp hybrid orbitals
e. Sigma bonds
f. Pi bonds
5

6. Keywords
g. Organic chemistry
h. Hydrocarbons
i. Alkanes
j. Alkenes
k. Alkynes
l. Cycloalkanes
6

7. Keywords
m. Aliphatic hydrocarbons
n. Aromatic hydrocarbons
o. Saturated hydrocarbons
p. Unsaturated hydrocarbons
q. Straight chain hydrocarbons
r. Branched hydrocarbons
7

8. Keywords
s. Structural isomers
t. Geometric isomers
u. Functional groups
v. Alcohols
w. Aldehydes
x. Carboxylic acids
8

9. Motivation
Organic Compounds and Smells
▰ Putrescine Cadaverine
▰ NH2(CH2)4NH2 NH2(CH2)5NH2
9

10. ▰ foul-smelling organic compounds
found in decaying animals
10

11. ▰ Limonene, C10H16
▰ source of the scent of lemons
11

12. ▰ Vanilin, C8H8O3
▰ gives the distinctive scent of vanilla
12

13. ▰ Cinnamaldehyde, C9H8O
▰ scent of cinnamon
13

14. ▰ Methyl Salicylate, C8H8O3
▰ responsible for the smell of oil of
wintergreen
14

15. The Valence Bond Theory
▰ Lewis structures and VSEPR theory provide
simple descriptions of bonding in
molecules. They treat all bonding to be due
to the pairing up of electrons which, if
accurate, should provide similar properties
for bonds of the same type.
15

16. The Valence Bond Theory
▰ However, experimental results show that
properties (such as bond energies, bond
lengths, etc.) vary and these cannot be
explained by the simple Lewis structure.
▰ A more accurate description of bonding
comes from quantum mechanics.
16

17. The Valence Bond Theory
▰ There are two quantum mechanical
theories of bonding: the valence bond
(VB) theory and the molecular orbital
theory.
17

18. The Valence Bond Theory
 when two single atoms of hydrogen
approach each other, there will be an
optimum distance between them where the
attractive forces of the nuclei will be
greatest and repulsion will be least. In this
state, the energy of the system is at a
minimum (lowest).
18

19. The Valence Bond Theory
▰ The system is most stable in this state and
we say that a bond has been formed, the
H—H bond.
▰ VB theory says that the bond is formed
from the overlap of the s orbitals of the H
atoms. (Overlap means that the electrons
occupy a common region in space).
19

20. The Valence Bond Theory
20

21. The Valence Bond Theory
▰ Because different orbitals overlap, the
differences in the properties of these bonds
(e.g. bond length and bond strength) can
be explained by VB theory unlike the Lewis
structures that treat all bonds alike.
21

22. Hybridization of Atomic Orbitals
▰ produces hybrid orbitals which have the
same energies.
sp3 hybridization
▰ Consider the molecule CH4 where C is
bonded to four H atoms in a tetrahedral
geometry. The valence electron
configuration of C is
22

23. Hybridization of Atomic Orbitals
▰ How can carbon form four bonds with
hydrogen in CH4 when it only has two
unpaired electrons?
▻ Because the energy gap between the 2s
and the 2p orbitals is small, one of the
electrons in the 2s orbital can be
promoted to the 2p orbital.
23

24. Hybridization of Atomic Orbitals
▰ Now the four unpaired electrons can form
four bonds of different types: one bond will
be the overlap of the 1s orbital of hydrogen
and the 2s orbital of carbon; the other three
will be from the overlap of the 1s orbital of
H and the 2p orbitals of C.
24

25. Hybridization of Atomic Orbitals
▰ To explain the bonding in CH4, valence
bond theory uses a theoretical concept of
hybrid orbitals.
▰ Hybrid orbitals are obtained from the
combination or mixing of two or more non
equivalent orbitals of the same atom.
25

26. Hybridization of Atomic Orbitals
▰ When one s orbital and three p orbitals are
combined through hybridization, four
equivalent sp3 hybrid orbitals result. These
sp3 hybrid orbitals are tetrahedrally
oriented. The shape of an sp3 orbital is not
symmetrical; it has a larger probability on
one side of the nucleus compared to the
other. 26

27. Hybridization of Atomic Orbitals
27

28. Hybridization of Atomic
Orbitals
▰ The four sp3 orbitals are oriented towards
the corners of a tetrahedron. The CH4
molecule is tetrahedral with bond angles of
109.50
▰ Other atoms also exhibit hybridization.
28

29. Hybridization of Atomic
Orbitals
▰ NH3 is pyramidal and the N atom is sp3
hybridized. The lone pair occupies an sp3
orbital.
▰ H2O is bent with bond angles close to
109.5. The O atom is sp3 hybridized.
29

30. Hybridization of Atomic
Orbitals
sp2 hybridization
▰ Consider the bonding in BF3. What is the
electron configuration of boron?
▰ How can boron form three bonds with
fluorine in BF3 when it only has only one
unpaired electrons?
30

31. Hybridization of Atomic
Orbitals
▰ The 2s and two 2p orbitals can be mixed to
form three hybrid orbitals called the sp2
hybrid orbitals.
▰ The sp2 hybrid orbitals have a trigonal
planar orientation. Therefore, all are on a
plane with angles of 1200.
31

32. Hybridization of Atomic
Orbitals
32

33. Hybridization of Atomic
Orbitals
 Draw the bonding in BF3 showing the
overlap of the 2p orbitals of fluorine and
the sp2 orbitals in boron.
33

34. Hybridization of Atomic
Orbitals
▰ Describe the bonding in ethylene, C2H4.
▰ From the Lewis structure, the geometry
around each carbon atom in ethylene is
trigonal planar.
34

35. Hybridization of Atomic
Orbitals
35
Side view of
sp2 hybridized
C atom
showing the
unhybridized
p orbital

36. Hybridization of Atomic
Orbitals
▰ Two types of covalent bonds in C2H4: the
sigma (σ) bonds and the pi (π) bonds.
▰ Sigma bonds are formed by end-to-end
overlap of the atomic orbitals with electron
density concentrated between the nuclei of
the bonding atoms.
36

37. Hybridization of Atomic
Orbitals
▰ Pi bonds are formed by the sideways
overlap of orbitals with the electron
density concentrated above and below the
plane of the nuclei of the bonding atoms.
▰ An end-to-end overlap is the most efficient
way to bond compared to a sideways
overlap.
37

38. Hybridization of Atomic
Orbitals
▰ Sigma bonds are relatively stronger than pi
bonds.
38

39. Formation of sigma and pi bonds
in ethylene
▰ How many sigma bonds are there in C2H4?
Name them.
39

40. Formation of sigma and pi bonds
in ethylene
▰ How many pi bonds are there in C2H4?
Name them.
▰ Note that a pi bond consists of two lobes
– one above the plane and another
below the plane.
40

41. Hybridization of Atomic
Orbitals
sp hybridization
▰ Describe the bonding in ethyne (also called
acetylene, C2H2).
▰ From the Lewis structure, the geometry
around each carbon atom in acetylene is
linear. The valence electron configuration
about each carbon atom is
41

42. Hybridization of Atomic
Orbitals
The sp hybridized
carbon showing the
two unhybridized p
orbitals
42

43. Hybridization of Atomic
Orbitals
▰ One electron from the 2s orbital of carbon
is promoted to the 2p. One 2s orbital and
one 2p orbital are mixed to form the two sp
orbitals leaving unpaired electrons in two
2p orbitals. The unhybridized p orbitals are
perpendicular to each other.
43

44. Hybridization of Atomic
Orbitals
▰ The hybridized sp orbitals of each carbon
atom overlap end-to-end forming a σ bond.
The unhybridized p orbitals of each carbon
atom overlap sideways forming two π
bonds.
44

45. Hybridization of Atomic
Orbitals
▰ The bonding in C2H2 showing the formation
of the σ and π bonds)
45

46. Geometrical Arrangements of
Hybrid Orbitals
46
Atomic
Orbitals
Hybrid
Orbitals
Geometry Bond
Angle
s, p sp linear 1800
s, p, p sp2 trigonal planar 1200
s, p, p, p sp3 tetrahedral 109.50

47. Exercises
1. Determine the hybridization of each carbon
atom (going left to right) in the following
molecules:
a. H3C — CH3
Draw the Lewis structure. Deduce the
geometry around the carbon
atoms. Determine the hybridization.
47

48. Exercises
b. H3C — CH2CH3
c. H3C — C = C — CH3
d. H3C — CH = O
e. H2C = C = CH2
2. How many sigma bonds and pi bonds are
in each of the molecules in #1?
48

49. Exercises
3. What is the hybridization of N in NH3?
4. What orbitals overlap in the formation of the
O — H bond in H2O?
5. What orbitals overlap in the formation of the
C — Cl bond in CH3Cl?
49

50. THE SPECIAL
NATURE OF
CARBON
50

51. ▰ About 200 year ago, organic chemistry was
defined as the study of compounds produced
by living things like plants and animals.
Organic compounds needed a ‘life force’ to
be produced. Compounds that were from
nonliving things like rocks were referred to as
inorganic.
51

52. ▰ All these changed in 1828 with the
experiment of Friedrich Wöhler.
▰ Wöhler synthesized urea (an organic
compound) from ammonium cyanate (an
inorganic compound). This marked a
turning point in Organic chemistry.
52

53. ▰ It dispelled the belief that organic
compounds could only be formed by
nature.
53

54. Special Nature of Carbon
▰ Carbon completes its octet by sharing
electrons and not by forming ions. It shares
its electrons with other carbon atoms
forming single, double, and triple bonds.
▰ It also shares its electrons and readily
forms bonds with atoms of other elements
like O, H, N, and the halogens.
54

55. Special Nature of Carbon
▰ The small radius of carbon allows it to
approach another carbon atom closely,
giving rise to short and strong covalent
bonds and stable compounds.
▰ Carbon can form four covalent bonds. This
allows it to form chains (straight, branched
or cyclic) in endless arrays.
55

56. Special Nature of Carbon
▰ Carbon can form millions of different
compounds. To date, over 20 million
organic compounds, both synthetic and
natural, are known compared with only
about 100,000 inorganic compounds.
▰ Carbon can form more compounds than
any other element in the periodic table.
56

57. Organic Compounds:
HYDROCARBONS
▰ A major group of organic compounds
▰ made up of only carbon and hydrogen
atoms.
▰ are further classified into aliphatic
hydrocarbons (those that do not contain a
benzene ring) and aromatic hydrocarbons
(those that contain a benzene ring).
57

58. Organic Compounds:
HYDROCARBONS
58

59. ALKANES
▰ have the general formula CnH2n+2 where n=1,
2, 3….
▰ only have single bonds
▰ also known as saturated hydrocarbons. They
are referred to as saturated hydrocarbons
because they contain the maximum number
of hydrogen atoms that can bond to the
59

60. ALKANES
Carbon atoms present; that is, they are
saturated with hydrogen atoms.
▰ In naming alkanes, the –ane suffix (ending) is
used. The name of the parent compound is
determined by the number of carbon atoms in
the longest chain.
60

61. ALKANES
61
No. of
atoms
Prefix No. of
atoms
Prefix
1 Meth- 6 Hex-
2 Eth- 7 Hept-
3 Prop- 8 Oct-
4 But- 9 Non-
5 Pent- 10 Dec-

62. 62
ALKANES

63. Do the following
a. Fill in the molecular formula and the
structural formula of straight chain pentane
up to decane.
b. How many bonds does each carbon atom
have in the compounds?
c. What is the geometry of each carbon
atom?
63

64. d. What is the bond angle around each
carbon atom?
e. What is the hybridization of each carbon
atom in hydrocarbons?
64

65. f. Describe the boiling points of the
hydrocarbons as the number of carbon
atoms increases and the chain gets longer.
g. Which of the hydrocarbons will be gases at
room temperature (Room Temperature
=250C)?
65

66. Structural Isomers
▰ Isomers are different compounds that have
the same chemical formula. There are two
ways of writing the structure of butane: n-
butane (where n stands for normal) and
isobutane. These are called structural
isomers.
66

67. Structural Isomers
▰ Structural isomers are molecules that
have the same molecular formula but
different structures.
▰ Alkanes are described as having straight
chains (such as n-butane) or branched
chains (such as isobutane).
67

68. Structural Isomers
n-butane
Straight chain isobutane
Boiling pt= - 42.10C branched chain
Boiling pt= - 11.70C
68

69. Structural Isomers
▰ For alkanes, the number of isomers
increases as the number of carbon atoms
increases.
▰ Butane has only 2 isomers, decane has 75
isomers and the alkane C30H62 has over
400 million possible isomers.
69

70. Structural Isomers
▰ this illustrates how carbon forms more
compounds than any other element
Exercise: Pentane has three structural
isomers. Draw them.
70

71. CYCLOALKANES
▰ Alkanes whose carbon atoms are joined in
rings
▰ they have the general formula CnH2n.
▰ The simplest cycloalkane is cyclopropane.
71

72. CYCLOALKANES
Cyclopropane cyclobutane cyclopentane
72

73. Reactions of Alkanes
1. Under suitable conditions, alkanes
undergo combustion reactions to
produce carbon dioxide and water.
CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)
2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(l)
73

74. Reactions of Alkanes
2. Alkanes undergo halogenation reaction
where one or more hydrogen atoms are
replaced by halogen atoms.
CH4(g) + Cl2(g) → CH3Cl(g) + HCl(g)
methyl chloride
74

75. Reactions of Alkanes
Under excess chlorine, the reaction proceeds
further:
CH3Cl(g) + Cl2(g) → CH2Cl2(g) + HCl(g)
methylene chloride
CH2Cl2(g) + Cl2(g) → CHCl3(g) + HCl(g)
chloroform
75

76. ALKENES
▰ hydrocarbons that contain at least one
carbon-carbon double bond
▰ also called olefins
▰ Their formula is CnH2n where n = 2, 3…
▰ classified as unsaturated hydrocarbons as
opposed to the alkanes which are saturated
hydrocarbons.
76

77. ALKENES
▰ Alkenes are unsaturated hydrocarbons –
compounds that have double or triple
bonds that enable them to add hydrogen
atoms.
▰ In naming alkenes, the –ene suffix (ending)
is used. The name of the parent compound
is determined by the number of carbon
atoms in the longest chain.
77

78. ALKENES
78

79. Geometric Isomers of Alkenes
 alkenes exhibit geometric isomers
 In the cis isomer, two particular atoms or
group of atoms are adjacent to each other
(same side of the double bond).
 In the trans isomer, the two groups are
across from each other.
79

80. Geometric Isomers of Alkenes
 The cis and trans isomers exhibit distinctly
different chemical and physical properties.
80

81. Geometric Isomers of Alkenes
81

82. Reactions of Alkenes
1. Addition Reactions: Unsaturated
hydrocarbons commonly undergo addition
reactions where one molecule adds to
another to form a single product.
82

83. Reactions of Alkenes
▰ Hydrogenation is an example of an
addition reaction where hydrogen is added
to compounds containing double bonds
usually in the presence of a catalyst.
83

84. Reactions of Alkenes
 Hydrogenation is very important in the food
industry particularly for vegetable oils.
84

85. Reactions of Alkenes
▰ Alkenes also undergo addition reactions
involving hydrogen halide, HX (where X is a
halogen).
C2H4(g) + HX(g) → H3CCH2X(g)
C2H4(g) + X2 (g) → CH2XCH2X(g)
85

86. ALKYNES
▰ Alkynes contain at least one CC triple bond.
▰ have the general formula CnH2n-2 where n =
2, 3,…
▰ In naming alkynes, the –yne suffix
(ending) is used. The name of the parent
compound is determined by the number of
carbon atoms in the longest chain.
86

87. ALKYNES
▰ Like the alkenes, the names of alkynes
indicate the position of the carbon-carbon
triple bond
87

88. ALKYNES
88

89. Reactions of Alkynes
a. Combustion
2C2H2(g) + 5 O2(g) → 4CO2(g) + 2H2O(l)
This reaction gives off a large amount of
heat; thus its use in oxyacetylene torches for
welding metals
89

90. Reactions of Alkynes
b. Addition reaction
Hydrogenation: C2H2(g) + H2(g) → C2H4(g)
Reaction with halogens and hydrogen halides:
C2H2(g) + HX(g) → C2H2CHX(g)
C2H2(g) + H2(g) → CHXCHX(g)
90

91. AROMATIC HYDROCARBONS
▰ Aromatic hydrocarbons are a class of
hydrocarbons whose molecules contain a
ring of six carbon atoms (benzyl ring)
attached.
▰ Its simplest member is benzene, C6H6, with
the following resonance structures:
91

92. AROMATIC HYDROCARBONS
The benzene structure is often written as:
92

93. AROMATIC HYDROCARBONS
▰ The group containing benzene less one
hydrogen atom (C6H5) is called a phenyl
ring.
93

94. AROMATIC HYDROCARBONS
▰ Other examples of aromatic hydrocarbons
▰ Toluene or 2-phenylpropane napthalene
methylbenzene
94

95. Simple Reactions of Aromatic
hydrocarbons
Substitution reactions – an atom or group of
atoms replaces an atom or group of
atoms in another molecule
95

96. Simple Reactions of Aromatic
hydrocarbons
96

97. ORGANIC COMPOUNDS:
FUNCTIONAL GROUPS
97

98. Functional groups
 is a group of atoms that is largely
responsible for the chemical behavior of the
parent molecule.
 Compounds containing the same
functional groups undergo similar
reactions.
98

99. Common Functional Groups
99
Class General
Formula
Functional
Group
Alcohol ROH — O — H Hydroxyl
group
Carboxylic
acid
RCOOH Carbonyl
group

100. Common Functional Groups
100
Ester
(R’=hydrocar
bon)
RCOOR’ Ester group
Aldehyde RCHO Carbonyl
group
Ketone
(R’=hydrocar
bon)
RCOR’ Carbonyl
group

101. Common Functional Groups
101
Amine
(R’, R” = H or
hydrocarbon)
RNR’R” Amino group
Amide
(R’, R” = H or
hydrocarbon)
RCONR’R” Amide group

102. Common Functional Groups
Alcohols
102

103. Common Functional Groups
▰ Methanol is the simplest alcohol. It is highly
toxic and causes blindness.
▰ Ethyl alcohol is a common solvent and
starting material for various commercial
uses. It is produced commercially by the
addition reaction of ethylene with water at
high pressure and temperature.
103

104. Common Functional Groups
▰ It is also produced from the fermentation of
sugar.
▰ An isomer, isopropyl alcohol, is commonly
called rubbing alcohol.
▰ Ethylene glycol is used as an antifreeze.
104

105. Common Functional Groups
▰ Ethyl alcohol can be oxidized by inorganic
oxidizing agents to acetaldehyde and acetic
acid.
105

106. Common Functional Groups
Ethers
106

107. Common Functional Groups
Ethers
▰ Ethers are usually prepared by a
condensation reaction. A condensation
reaction is characterized by the joining of
two molecules and the elimination of a
small molecule, usually water.
107

108. Common Functional Groups
108

109. Common Functional Groups
Aldehydes and Ketones
▰ The functional group in aldehydes and
ketones is the carbonyl group. A common
aldehyde is formaldehyde. An aqueous
solution of formaldehyde is used in the
laboratory to preserve animal specimens.
109

110. Common Functional Groups
▰ A common ketone is acetone, which is
mainly used as solvent for organic
compounds and as nail polish remover.
Alcohols can be oxidized to produce
aldehydes and ketones:
110

111. Common Functional Groups
▰ Alcohols can be oxidized to produce
aldehydes and ketones:
111

112. Common Functional Groups
Carboxylic acids
▰ The functional group in carboxylic acids is
the carboxyl group, -COOH. Among the
common carboxylic acids are formic acid,
acetic acid, and butyric acid.
112

113. Common Functional Groups
113
• Carboxylic acids can be produced by the oxidation
of alcohols and aldehydes.
• Carboxylic acids also react with alcohols to
produce esters.

114. Common Functional Groups
Esters
▰ Esters are used in flavoring and perfumery
owing to their characteristic smells. The
smell of many fruits come from esters such
as those given in the motivation section.
114

115. ▰ A common reaction of esters is
saponification.
▻ In this reaction, an ester reacts with
aqueous NaOH solution to produce back
the carboxylic acid and the alcohol. This
reaction originates from soapmaking.
115

116. ▻ Soap (Latin “sapo”) was originally
produced by the hydrolysis of fats.
116

117. POLYMERS
117

118. What are polymers?
▰ Polymers are large molecular compounds
made up of many repeating units called
monomers.
▰ They can be natural or synthetic. They are
sometimes called macromolecules because
of their high molar masses.
118

119. What are polymers?
▰ The word polymer comes from the Greek
“poly” (meaning many) and “mer” (meaning
part or segment). Therefore a polymer
means many parts.
▰ Natural polymers occur in nature.
Synthetic polymers are manmade and
synthesized in the laboratory.
119

120. What are polymers?
120

121. Making Polymers
▰ Polymerization is the chemical reaction by
which the monomers are linked together to
form polymers.
▰ There are several types of polymerization
reactions. The basic types are the addition
polymerization and the condensation
polymerization reactions.
121

122. Making Polymers
1. Addition polymerization
▰ In addition polymerization, the entire
monomer becomes part of the polymer.
They involve molecules with double bonds
or triple bonds. Consider the formation of
polyethylene, a stable polymer used
widely as packaging wrap.
122

123. Making Polymers
▰ The polymerization reaction consists of
three steps: initiation, propagation and
termination.
123

124. Making Polymers
▰ Polyethylene is an example of a
homopolymer – a type of polymer where
there is only one type of monomer.
124

125. Other examples of monomers
used to produce polymers
125
Monomer Polymer
Tetrafluoroethylene Polytetrafluoroethylene
(Teflon)
Vinyl chloride Polyvinylchloride
(PVC)

126. Other examples of monomers
used to produce polymers
126
Monomer Polymer
Styrene Polystyrene
Propene Polypropene
(or polypropylene)

127. ▰ In the examples, ethylene (CH2 = CH2) and
tetrafluoroethylene (CF2 = CF2) are
symmetric monomers (the carbons have
the same substituents) while vinyl chloride,
styrene, and propene are asymmetric
monomers (the carbons in the monomer
have different substituents).
127

128. ▰ The examples (polyethylene, polystyrene,
polypropylene, and Teflon) are synthetic
polymers.
128

129. 2. Condensation Polymerization
▰ Condensation polymers are those formed
through a condensation reaction – where
monomers join together at the same time
losing a small molecule like water as by-
product.
129

130. ▰ The reaction of a dicarboxylic acid and a
dialcohol to produce a polyester
130

131. ▰ the polymer polyethylene terephthalate
(PET or sometimes called PETE) is formed
by the reaction of terephthalic acid and
ethylene glycol. PET is a polyester.
131

132. ▰ The reaction of a dicarboxylic acid and a
diamine to produce a polyamide (such as
nylon).
132

133. Polymer Arrangements &
Structures
▰ Polymers can be arranged in a number of
ways. The arrangement of the polymer
chains affects their properties such as
whether they are stiff or rigid, crystalline or
amorphous.
133

134. Polymer Arrangements &
Structures
▰ A linear polymer is a one where the
arrangement of atoms is like that of a long
chain. This long chain is often referred to as
the backbone. Atoms or small groups of
atoms attached to the long chain are called
pendant atoms.
134

135. Polymer Arrangements &
Structures
135

136. Polymer Arrangements &
Structures
▰ The arrangement of the pendant atoms or
pendant groups attached to the backbone
gives different properties to the polymer.
▰ Three distinct arrangements are observed:
syndiotactic, isotactic, or atactic.
136

137. Polymer Arrangements &
Structures
▰ The isotactic arrangement is where all the
pendant groups or substituents
(represented by R — ) are on the same
side of the polymer chain. They pack
efficiently resulting in polymers with high
melting point, high crystallinity, and superior
mechanical strength.
137

138. Polymer Arrangements &
Structures
▰ A syndiotactic polymer chain is one where
the substituent group alternates from left to
right of the asymmetric carbons. They pack
less efficiently than isotactic chains.
138

139. Polymer Arrangements &
Structures
▰ In atactic polymers, the substituents occur
randomly. Therefore, they do not pack well.
These polymers are rubbery, not
crystalline, and relatively weak.
139

140. Polymer Arrangements &
Structures
140

141. Polymer Arrangements &
Structures
141

142. Polymer Arrangements &
Structures
142
Atactic

143. Polymer Arrangements &
Structures
▰ Branched chain polymers are more
flexible and less dense than straight
chained polymers. Example: high density
polyethylene (HDPE) polymers are used for
firm plastic bottles and containers while low
density polyethylene (LDPE) are used for
plastic food bags and plastic wraps.
143

144. Polymer Arrangements &
Structures
▰ Sometimes, the polymer chains are cross-
linked as in the case of vulcanized rubber.
Rubber is a natural organic polymer
formed by the addition of the monomer
isoprene. In vulcanized rubber, the polymer
strands of isoprene are crossed linked or
bridged by short sulfur chains.
144

145. Polymer Arrangements &
Structures
▰ The crosslinks tie or bind the polymer
strands together.
145

146. Polymer Arrangements &
Structures
▰ when these crosslinked polymers are
heated, the strands cannot flow past each
other, they do not melt or break apart.
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147. Polymer Arrangements &
Structures
▰ Sometimes, there are two or more different
monomers that are joined together to form
a polymer – it is called copolymer.
▰ Let us say that the two monomers are
monomer A and monomer B.
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148. Polymer Arrangements &
Structures
▰ These two monomers may be arranged in
several ways in a polymer giving different
physical properties to the polymer.
- A - B - A - B - A - B - A - B - Alternating
copolymer
- A - A - B - A - B - B - A - B - A Random
copolymer
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149. Polymer Arrangements &
Structures
- A - A - A - A - A - B - B - B - B - B - Block
copolymer
▰ Examples of copolymers are Saran wrap,
styrene butadiene rubber – used for soles
of shoes)
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150. PLASTICS & POLYMERS
Plastic
 The word ‘plastic’ comes from the Greek
‘plastikos’ meaning ‘to mold’.
 Generally, plastics refer to synthetic
polymers.
 Plastics are polymers but not all polymers
are plastic.
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151. PLASTICS & POLYMERS
 Plastics are classified into two types:
thermoplastics and thermosets.
 Thermoplastics are those that keep their
plastic properties,
 they melt when heated and harden when
cooled.
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152. PLASTICS & POLYMERS
 made of long linear polymer chains that
are weakly bonded to each other. When
heated, the bonds are easily broken and
the polymer chains easily glide past
each other. Therefore, they are readily
remolded
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153. PLASTICS & POLYMERS
 Thermosets are permanently “set” once
they are formed,
 they cannot be melted or reshaped, if
enough heat is added, they will crack or
become charred
153

154. PLASTICS & POLYMERS
 are made up of linear chains that are
cross-linked to one another preventing
the material from being melted and
reformed.
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155. Universal Recycling Codes
155

156. Universal Recycling Codes
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157. 157
Thank You!
Any questions?

158. CREDITS
Special thanks to all the people who made
and released these awesome resources for
free:
▰ Presentation template by SlidesCarnival
▰ Photographs by Startup Stock Photos
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