Transcript Chapter 22 Organic and Biological Molecules 1

Chapter 22
Organic and Biological
Molecules
1
Organic Chemistry and Biochemistry
•The study of carbon-containing
compounds and their properties.
•The vast majority of organic
compounds contain chains of rings
of carbon atoms.
•The study of the chemistry of living
matter
2
Hydrocarbons
•
compounds composed of carbon and
hydrogen.
Saturated compounds (alkanes) have
the maximum number of hydrogen
atoms attached to each carbon atom
Saturated: carbon-carbon bonds are all
single - alkanes [CnH2n+2]
H H
•
•
H C
C H
H H
3
 Unsaturated compounds have fewer
hydrogen atoms attached to the
carbon chain than alkanes
• Unsaturated: They contain carboncarbon multiple bonds (double or
triple)
H H
H C
H
4
C
H
C
H
22.1 Alkanes: Saturated
hydrocarbons
• Saturated hydrocarbons, CnH2n+2
– “Saturated” because they can’t take any
more hydrogen atoms
– Straight chains are H3C–(CH2)n–2–CH3
– Waxes, oils, & fuel gases as n decreases.
5
Alkanes: Saturated Hydrocarbons
• Hydrocarbons are molecules composed of carbon &
hydrogen
– Each carbon atom forms 4 chemical bonds
– A saturated hydrocarbon is one where all C - C bonds are
“single” bonds & the molecule contains the maximum number
of H-atoms
– Saturated hydrocarbons are called ALKANES
6
Methane is a tetrahedral molecule
7
The Lewis structure of ethane.
8
A ball-and-stick model of ethane.
9
Propane
10
Butane
11
The First 10 “Normal” Alkanes
•
•
•
•
•
•
•
•
•
•
12
Name
Formula
M.P.
B.P.
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
-183
-172
-187
-138
-130
-95
-91
-57
-54
-30
-162
-89
-42
0
36
68
98
126
151
174
# Structural Isomers
1
1
1
2
3
5
9
18
35
75
C1 - C4 are Gases
at Room Temperature
C5 - C16 are Liquids
at Room Temperature
The C-H Bonds in Methane
13
IUPAC Rules for Naming Branched Alkanes
• Find and name the parent chain in the hydrocarbon this forms the root of the hydrocarbon name
• Number the carbon atoms in the parent chain
starting at the end closest to the branching
• Name alkane branches by dropping the “ane” from
the names and adding “yl”. A one-carbon branch is
called “methyl”, a two-carbon branch is “ethyl”,
etc…
• When there are more than one type of branch (ethyl
and methyl, for example), they are named
alphabetically
14 • Finally, use prefixes to indicate multiple branches
Rules for Naming Alkanes
1. For alkanes beyond butane, add -ane
to the Greek root for the number of
carbons.
C-C-C-C-C-C : hexane
2. Alkyl substituents: drop the -ane and
add -yl
-C2H5 is ethyl
15
16
Rules for Naming Alkanes
3.Positions of substituent groups are
specified by numbering the longest
chain sequentially.
C

C-C-C-C-C-C
3-methylhexane
• Start numbering at the end closest to
the branching
4.Location and name are followed by root
alkane name. Substituents in
alphabetical order and use di-, tri-, etc.
17
Normal vs Branched Alkanes
• Normal alkanes consist of
continuous chains of
CH2
CH2
carbon atoms
CH3
CH2
CH3
• Alkanes that are NOT
continuous chains of
carbon atoms contain
branches
CH3
CH2
CH
CH3
• The longest continuous
chain of carbons is called
CH3
the parent chain
18
Structural Isomerism
• Structural isomers are
molecules with the same
chemical formulas but
different molecular
structures - different
“connectivity”.
• They arise because of the
many ways to create
branched hydrocarbons.
CH2
CH2
CH3
CH2
CH3
n-pentane, C5H12
CH3
CH2
CH3
CH
CH3
19
2-methlbutane, C5H12
Isomer Naming
• Older conventions would have that
as “isooctane,” but a good IUPAC
name results from the following:
– Name the longest C chain (pentane)
– List the side groups in alphabetical
order with Greek prefixes
(trimethylpentane)
– Supply (smallest possible) positional
indices (2,2,4 trimethylpentane)
20
Example : Show the structural formula
of 2,2-dimethylpentane
2
• The parent chain is indicated
4
by the ROOT of the name CH2 5
CH2 3
1
“pentane”. This means there CH
CH3
CH2
3
are 5 carbons in the parent
chain.
• “dimethyl” tells us that there are
TWO methyl branches on the
parent chain. A methyl branch is
made of a single carbon atom.
CH3
4
CH2
C
1
CH3
21
CH2
3
CH3
CH3
5
• “2,2-” tell us that BOTH methyl
branches are on the second
carbon atom in the parent chain.
Example: Structural formula of
3-ethyl-2,4-dimethylheptane?
2
4
• The parent chain is indicated
CH2 5
CH2 3
1
by the ROOT of the name CH2
CH2
“heptane”. This means there CH3
are 7 carbons in the parent
chain.
H2C 6
CH3
CH3
CH
CH
CH3
22
CH3
CH
CH2
CH2
CH2
7
CH3
• “2,4-dimethyl” tells us there are
TWO methyl branches on the
parent chain, at carbons #2 and
#4.
• “3-ethyl-” tell us there is an ethyl
CH3 branch (2-carbon branch) on
carbon #3 of the parent chain.
Example: 2,3,3-trimethyl-4-propyloctane
• The parent chain is indicated
by the ROOT of the name “octane”. This means there
are 8 carbons in the parent
chain.
3
5
4
2
6
7
1
8
CH3
2
1
23
3
5
4
6
7
• “2,3,3-trimethyl” tells us there are
CH3THREECmethyl branches
CH2 - one on
CH #2 andCH
CH2#3.
carbon
two on carbon
8
CH3
CH3
• “4-propyl-”
tellCH
us there
is CH
a propyl
2
2
branch (3-carbon branch)
CH2 on CH3
carbon #4 of the parent chain.
CH3
Example : Name the molecules shown
• parent chain has 5 carbons “pentane”
• two methyl branches - start
counting from the right - #2
and #3
• 2,3-dimethylpentane
3
24
4
5
CH3
CH
CH2
CH3
CH
CH3
CH3
• parent chain has 8 carbons “octane”
• two methyl branches - start
counting from the left - #3 and #4
• one ethyl branch - #5
• name branches alphabetically
5-ethyl-3,4-dimethyl octane
Reactions of alkanes
• Combustion reactions
2C4H10 + 13 O2
8CO2 + 10 H2O(g)
• Substitution Reactions
CH4 + Cl2
25
CH3Cl + HCl
CH3Cl + Cl2
CH2Cl2 + HCl
CH2Cl2 + Cl2
CH Cl3 + HCl
CHCl 3  Cl 2
h
CCl 4  HCl
Dehydrogenation Reactions
CH3CH3
CH2
CH2
Ethylene
26
Cyclic alkanes
• A cycloalkane is made of a hydrocarbon
chain that has been joined to make a “ring”.
H2
C
109.5° bond angle
CH2
CH3
CH3
n-propane
C3H8
H2C
60° bond angle
unstable!!
CH2
cyclopropane
C3H6
•Note that two hydrogen atoms were lost in forming the ring
27
•What is the general formula for a cycloalkane?
Cyclic alkanes, CnH2n
• If the two end C’s lose 1 H each, they
have free valence to close a ring
• Again, properties similar to
straight chains.
– Can now have conformational
isomers!
– E.g., BOAT cyclohexane versus
CHAIR
28
Cyclohexane - Boat & Chair Conformations
• Cyclohexane is NOT a planar molecule. To achieve
its 109.5° bond angles and reduce angle strain, it
adopts several different conformations.
• The BOAT and CHAIR (99%) are two conformations
29
Unsaturated hydrocarbomns
22.2 Alkenes and Alkynes
Alkenes: hydrocarbons that contain a
carbon-carbon double bond. [CnH2n]
C=C
Ethene
CC=C
propene
Alkynes: hydrocarbons containing a
carbon-carbon triple bond. [CnH2n-2]
C C
Ethyne
CCCCC
2-pentyne
30
Alkenes & Alkynes
• The suffix for the
• Alkenes are
parent alkane chains
hydrocarbons that
are changed from
contain at least one
“ane” to “ene” and
carbon-carbon
“yne”
double bond
– e.g. ethene, ethyne
• Alkynes are
hydrocarbons that • Where it is ambiguous,
the BONDS are
contain at least one
carbon-carbon triple numbered like
branches so that the
bond
location of the multiple
31
bond may be indicated
Alkenes, CnH2n
• Cycle formation isn’t the only possible
result of dehydrogenation.
• Adjacent C’s can double bond, C=C,
making an (unsaturated) alkene.
Sp2
32
The Bonding in Ethylene
33
Nomenclature for Alkenes
1.Root hydrocarbon name ends in -ene
C2H4; CH2=CH2
is ethene
2.With more than 3 carbons, double
bond is indicated by the lowest
numbered carbon atom in the bond.
C=CCC is 1-butene
34
Alkene Isomers
•
X
While an
CX2Y2 has only 1 isomer,X C Y
Y
• (every X and Y is adjacent to all the others)
sp3
• the sp2 alkene C2X2Y2 has cis & trans
isomers (where X is or isn’t on the same side of = as X).
– For longer hydrocarbons, cis & trans refer
to the side the chain extends:
35
Cis and Trans Isomers
Double bond is fixed
Cis/trans Isomers are possible
CH3
CH3
CH = CH
cis
36
CH3
CH = CH
trans
CH3
Addition Reactions
•
37
Weaker  bonds are broken and
new (stronger)  bonds are formed
to atoms being added.
Hydrogenation
Adds a hydrogen atom to each carbon
atom of a double bond
H H
H H
Ni
H–C=C–H + H2
H–C–C–H
H H
ethene
38
ethane
CH3-CH3
Halogenation
Adds a halogen atom to each carbon
atom of a double bond
H H
H H
Ni
H–C=C–H + Cl2
H–C–C–H
Cl Cl
ethene
39
dichloro ethane
Halogenation Reactions
CH2
CHCH2CH2CH2 + Br2
CH2Br
CHBrCH2CH2CH2
1,2-dibromopentane
40
Alkynes, CnH2n–2
Carbon-carbon triple bonds
Names end in -yne
HCCH
ethyne(acetylene)
HCC-CH3
propyne
41
The Bonding in Acetylene
42
Naming Alkenes and Alkynes
When the carbon chain has 4 or more C atoms,
number the chain to give the lowest number to the
double or triple bond.
1
2 3 4
CH2=CHCH2CH3
1-butene
CH3CH=CHCH3
2-butene

2-butyne
CH3CH CHCH3
43
Question
Write the IUPAC name for each of the following
unsaturated compounds:
2-pentyne
A.
CH3CH2CCCH3
CH3
B.
CH3C=CHCH3
2-methyl-2-butene
44
Question
• Name the following compound
CH3CH2C CCHCH2CH3
CH2
CH3
1
2
3
4 5
6
7
CH3CH2C CCHCH2CH3
CH2
CH3
45
5-ethyl-3-heptyne
Additions reactions:Hydrogenation and
Halogenation
Hydrogens and halogens also add to the triple
bond of an alkyne.
Br Br
CH3C CCH2CH3
+ Br2
CH3C CCH2CH3
Br Br
46
22.3 Aromatic hydrocarbons
Unsaturated Cyclic hydrocarbons
• Alternating single/double bond
cycles occur in many organic
molecules
– This class is called “aromatic” (by
virtue of their aroma).
– The  structure is often preserved in
their chemical reactions; they don’t
add, they substitute instead.
47
Lewis structures for the benzene ring.
48
Benzene C6H6
sp2
sp2
49
sp2
Shorthand notation for benzene rings
50
The bonding in the benzene ring is a
combination of different Lewis structures.
51
Aromatic Hydrocarbons
Substitution reaction
Nitroobenzene
Chlorobenzene
Cl
+ Cl2
benzene
52
FeCl3


HNO3
H
CH
Cl
N 3
O
3
-NO2
-CH3
Toluene
+ HCl
+H2O
+HCl
53
Nomenclature of benzene derivatives
54
More Complex Aromatic Systems
55
22.4 Hydrocarbon Derivatives
(Functional Groups)
 Molecules that are fundamentally



56
hydrocarbons but have additional atoms
or group of atoms called functional groups
Part of an organic molecule where
chemical reactions take place
Replace an H in the corresponding alkane
Provide a way to classify organic
compounds
The Common Functional Groups
Class
Halohydrocarbons
Alcohols
Ethers
Aldehydes
57
General Formula
RX
ROH
ROR
R
O
C H
Class
Ketones
General Formula
R
Carboxylic Acids
Esters
Amines
58
R
O
C R'
O
C OH
R
O
C OR'
R
NH2
Some Types of Functional Groups
Haloalkane
Alcohol
-F, -Cl, -Br CH3Cl
-OH
CH3OH
Ether
-O-
Aldehyde
O
O
C H
O
CH3CH
C
CH3CCH3
Ketone
59
CH3-O-CH3
O
More Functional Groups
Carboxylic acid -COOH
CH3COOH
Ester
-COO-
CH3COOCH3
Amine
-NH2
CH3NH2
Amide
-CONH2
CH3CONH2
60
61
Haloahydrocarbons
An alkane in which one or more H atoms is
replaced with a halogen (F, Cl, Br, or I)
CH3Br
bromomethane
(methyl bromide)
Br
CH3CH2CHCH3
2-bromobutane
Cl
chlorocyclobutane
62
Nomenclature
Name the following:
Br
bromocyclopentane
Cl
1 2
3
1,3-dichlorocyclohexane
Cl
63
Substituents
List other attached atoms or groups in
alphabetical order
Br = bromo, Cl = chloro
Cl
Br
1
2
3
4
5
CH3CHCH2CHCH2CH2CH3
4-bromo-2-chloroheptane
64
Nomenclature
The name of this compound is:
Cl
CH3
CH3CH2CHCH2CHCH3
65
1)
2,4-dimethylhexane
2)
4-chloro-5-methylhexane
3)
4-chloro-2-methylhexane
Solution
The name of this compound is:
Cl
6
5
4
CH3
3
2
1
CH3CH2CHCH2CHCH3
3.
66
4-chloro-2-methylhexane
Alcohols: R–OH
• The –OH makes alcohol polar enough
to hydrogen bond.
• Thus, they are water soluble
• Ethanol is a fermentation product acid.
C6H12O6
Glucose
•
2CH3CH2OH
Ethanol
+ 2 CO2
Methanol is produced industrially by hydrogenation
of carbon monoxide
CO + 2H2O
67
yeast
CH3OH
Methanol
Uses of alcohols
• Methanol is used to synthesize adhesives,
fibers, plastics and recently as motor fuel
• It is toxic to human and can lead to blindness
and death
• Ethanol can be added to gasoline to form
gasohol and used in industry as solvent
• Commercial production of ethanol:
CH2=CH2 + H2O
CH3CH2OH
68
Classes of alcohols
Alcohols can be classified according to the number
of hydrocarbon fragments bonded to the carbon
where the –OH group is attached
R
CH2OH Primary alchol
R
CHOH Secondary alcohol
R'
R
R' C OH Tertiary alcohol
69
R"
Naming Alcohols
 In IUPAC name, the -e in alkane name is
replaced with -ol.
CH4 methane
CH3OH methanol
(methyl alcohol)
CH3CH3 ethane
CH3CH2OH ethanol
70
(ethyl alcohol)
OH
Phenol
(Aromatic alcohol)
71
More Names of Alcohols
 IUPAC names for longer chains number the
chain from the end nearest the -OH group.
CH3CH2CH2OH
1-propanol
OH
CH3CHCH3
CH3
5
2-propanol
OH
2
CH3CHCH2CH2CHCH3
72
5-methyl-2-hexanol
Some Typical Alcohols
OH
“Rubbing alcohol” CH3CHCH3
2-propanol (isopropyl alcohol)
Antifreeze
HO-CH2-CH2-OH
1,2-ethanediol (ethylene glycol)
OH
glycerol
HO-CH
-CH-CH
OH
2
2
73
Example
Name the following alcohols:
A.
OH
3-methyl-2-pentanol
CH3CHCHCH2CH3
CH3
OH
B.
Cyclobutanol
74
Reactions of Alcohols
Combustion
CH3OH + 2O2
CO2 + 2H2O + Heat
Dehydration
H OH
heat
H-C-C-H
75
H H
alcohol
H-C=C-H + H2O
H H
alkene
Ethers
• Contain an -O- between two carbon groups
• Simple ethers named from -yl names of the
attached groups and adding ether.
CH3-O-CH3
dimethyl ether
CH3-O-CH2CH3 ethyl methyl ether
76
Aldehydes and Ketones
 In an aldehyde, an H atom is attached to a
carbonyl group
O
carbonyl group

CH3-C-H
 In a ketone, two carbon groups are attached to
a carbonyl group
77
O

CH3-C-CH3
carbonyl group
Naming Aldehydes
 IUPAC Replace the -e in the alkane name -al
 Common Add aldehyde to the prefixes form
(1C), acet (2C), propion(3), and butry(4C)
O
O
O
methane

ethane 
propane 
H-C-H
CH3-C-H
CH3CH2C-H
methanal
ethanal
propanal
(formaldehyde) (acetaldehyde) (propionaldehyde)
78
Aldehydes as Flavorings
O
O
CH
CH
O
CH=CH CH
HO
OCH3
Benzaldehyde
(almonds)
79
Vanillin
(vanilla beans)
Cinnamaldehyde
(cinnamon)
Naming Ketones
 In the IUPAC name, the -e in the alkane name is
replaced with -one
 In the common name, add the word ketone
after naming the alkyl groups attached to the
O
carbonyl group
cyclohexane
80
O
 propane
CH3 -C-CH3
O
 butane
CH3-C-CH2-CH3
Propanone
2-Butanone
Cyclohexanone
(Dimethyl ketone) (Ethyl methyl ketone)
Acetone
Preparation of aldehydes and Ketones
They are produced by oxidation of alcohols:
CH3CH2OH
Oxidation
CH3C
Primary alcohol
Oxidation
CH3CHCH3
OH
Secondary alcohol
81
O
acetaldehyde
H
ethanal
CH3CCH3 acetone
propanone
O
Question
Classify each as an aldehyde (1), ketone (2)
or neither(3).
O

A. CH3CH2CCH3
CH3
O

C. CH3-C-CH2CH
82
CH3
B. CH3-O-CH3
O
D.
Solution
Classify each as an aldehyde (1), ketone (2)
or neither(3).
O

A. CH3CH2CCH3
CH3
2
O

C. CH3-C-CH2CH 1
83
CH3
B. CH3-O-CH3 3
O
D.
2
Question
Name the following
O

A. CH3CH2CCH3
CH3
O

C. CH3-C-CH2CH
CH3
84
O
B.
Solution
O

A. CH3CH2CCH3
B.
O
2-butanone (ethyl methyl ketone)
CH3
O

C. CH3-C-CH2CH
CH3
2,2-dimethylbutanal
85
cyclohexanone
Question
Draw the structural formulas for each:
A. 3-Methylpentanal
B. 2,3-Dichloropropanal
C. 3-Methyl-2-butanone
86
Solution
Draw the structural formulas for each:
CH3
O

A. 3-Methylpentanal
CH3CH2CHCH2CH
Br O

B. 2,3-Dibromopropanal
Br-CH2CHCH
O

C. 3-Methyl-2-butanone
CH3CHCCH3
87
CH
Carboxylic Acids and Esters
Carboxyl Group
Carboxylic acids contain the carboxyl group
as carbon 1.
O
R

CH3 — C—OH :
CH3—COOH
carboxyl group
88
Naming Carboxylic Acids
Formula
IUPAC
alkan -oic acid
Common
prefix – ic acid
HCOOH
methanoic acid
formic acid
CH3COOH
ethanoic acid
acetic acid
CH3CH2COOH
propanoic acid
propionic acid
CH3CH2CH2COOH butanoic acid
89
butyric acid
Naming Rule for Carboxylic acids
• Identify longest chain
• (IUPAC) Number carboxyl carbon as 1
CH3
|3
4
1
2
CH3 — CH—CH2 —COOH
IUPAC
3-methylbutanoic acid
90
Question
Give IUPAC name:
A.
CH3COOH
CH3
|2
B.
91
CH3CHCOOH
Solution
A.
CH3COOH
ethanoic acid; acetic acid
CH3
|
B.
CH3CHCOOH
2-methylpropanoic acid;
92
Preparation of carboxylic acids
• Oxidation of primary alcohols
KMnO4
CH3CH2OH
93
CH3COOH
Reaction of carboxylic acid with alcohol
Esterification
O
CH3C OH
Carboxylic acid
+
H OCH2CH3
Alcohol
O
CH3C OCH2CH3
Ester
94
+
H2O
Esters
In a ester, the H in the carboxyl group is
replaced with an alkyl group
O

CH3 — C—O —CH3 :
CH3—COO —CH3
ester group
95
•Esters give fruity odors
Naming Esters
• The parent alcohol is named first with a –yl
ending
• Change the –oic ending of the parent acid to
–ate
acid
alcohol
O

methyl
CH3 — C—O —CH3
Ethanoate
methyl ethanoate (IUPAC)
(acetate)
methyl acetate (common)
96
Some esters and their names
Flavor/Odor
Raspberries
HCOOCH2CH3
ethylmethanoate (IUPAC)
ethylformate (common)
Pineapples
CH3CH2CH2 COOCH2CH3
ethylbutanoate (IUPAC)
ethylbutyrate (common)
97
Question
Give the IUPAC and common names of the
following compound, which is responsible
for the flavor and odor of pears.
O

CH3 — C— O —CH2CH2CH3
98
Solution
O

propyl
CH3 — C—O —CH2CH2CH3
propylethanoate (IUPAC)
propyl acetate (common)
99
Question
Draw the structure of the following compounds:
A. 3-bromobutanoic acid
B. Ethyl propionoate
100
Solution
A. 3-bromobutanoic acid
Br
|
CH3CHCH2COOH
B. Ethyl propionoate
O

CH3 CH2 COCH2CH3 CH3CH2COOCH2CH3
101
Hydrolysis of esters
• Esters react with water and acid catalyst
• Split into carboxylic acid and alcohol
O
-OH
 H
H+
H — C—O—CH2CH3 + H2O
O

H — C—OH
102
+ HO—CH2CH3
Amines
• Organic compounds of nitrogen N;
derivatives of ammonia
• Classified as primary, secondary, tertiary
CH3
CH3


CH3—NH2 CH3—NH CH3—N — CH3
Primary
one N-C
bond
103
Secondary
two N-C
bonds
Tertiary
three N-C
bonds
Naming Amines
IUPAC aminoalkane
CH3CH2NH2
aminoethane
(ethylamine)
Common alkylamine
CH3—NH —CH3
N-methylaminomethane
(dimethylamine)
NH 2
NH CH3
NH2
|
CH3CHCH3
2-aminopropane
(isopropylamine)
104
Aniline
N-methylaniline
Question
Give the common name and classify:
A. CH3NHCH2CH3
CH3
|
B. CH3CH2NCH3
105
Solution
A. CH3NHCH2CH3
ethylmethylamine, (Secondary)
CH3
|
B. CH3CH2NCH3
ethyldimethylamine, (Tertiary)
106
Question
Write a structural formula for
A.
2-aminopentane
B.
1,3-diaminocyclohexane
107
Solution
A.
B.
1-aminopentane
CH3CH2CH2CH2CH2-NH2
1,3-diaminocyclohexane
NH2
NH2
108
Polymers
Poly= many; mers=parts
•
Polymers are large, usually chainlike
molecules that are built from small
molecules called monomers joined by
covalent bonds
Monomer
Polymer
Ethylene
Polyethylene
Vinyl chloride
Polyvinyl
chloride
Tetrafluoroethylene Teflon
109
110
Some common synthetic polymers, their
monomers and applications
111
Types of Polymerization
Addition Polymerization: monomers
“add together” to form the polymer,
with no other products. (Teflon)
Condensation Polymerization: A
small molecule, such as water, is
formed for each extension of the
polymer chain. (Nylon)
112
Addition Polymerization
H
H
C C
H
H
OH
H H
H C C
OH H
A species with
an unpaired
electron such as
hydroxyl free radical
The polymerization process
Is initiated by a free radical
H
H
C C
H
H
H H
H C C
H H H H
H C C C C
OH H H H
Free radical attacks and break
The  bond of ethylene molecule
To form a new free radical
OH H
• Repetition of the process thousands of times creates a long chain
polymer
• The process is terminated when two radicals react to form a bond;
113
thus there will be no free radical is available for further repetitions.
another
(Polythene)
• Depending upon conditions of polymerization, the
product may be branched or linear polyethylene
114
115
116
117
118
119
120
Condensation Polymerization
Formation of Nylon
H
H
O
O
N (CH2)6 N
C (CH2)4 C
H
H
H O
O H
Adipic acid
Hexamethylendiamine
Diamine
Dicarboxylic acid
H
H
121
N
H O
O
(CH2)6 N C (CH2)4 C
O H
Dimer
+ H2O
• Small molecule such as H2O is formed
from each extension of the polymer chain
• both ends are free to react
Nylon
H
(
122
N
H O
O
(CH2)6 N C (CH2)4 C )n
123
Proteins
• Natural polymers made up of -amino
acids (molecular weight from  6000 to
>1,000,000 g/mol).
1. Fibrous Proteins: provide structural
integrity and strength to muscle, hair and
cartilage.
124
Proteins
2. Globular Proteins:

Roughly spherical shape

Transport and store oxygen and
nutrients

Act as catalysts

Fight invasion by foreign objects

Participate in the body’s regulatory
system

Transport electrons in metabolism
125
-Amino Acids
NH2 always attached to the -carbon (the
carbon attached to COOH)
H
H2N C
R
•C = -carbon
126
COOH
Bonding in -Amino Acids
•
The protein polymer is built by condensation reaction
between amino acids
H
•

•
H O H H
N C
H
R
C
N C

R'
O
+ H2O
C
OH
Dipeptide
A peptide linkage (amide group)
•There are 20 amino acids commonly found in proteins.
• Additional condensation reaction produces
polypeptide eventually yielding a protein
127
The 20 Alphaamino Acids
found in
most
proteins
128
Levels of Structure
•Primary: Sequence of amino acids
in the protein chain. (lycine-alanineleucne: (lys-ala-leu).
– So many arrangements can be
predicted.
Tripeptide containing
Glycine, Cysteine, and
Alanine
129
Levels of Structure
•Secondary: The arrangement of the protein chain
in the long molecule (hydrogen bonding determines
this).
• Hydrogen bonding between lone pairs on an
oxygen atom in the carbonyl group of an amino acid
and a hydrogen atom attached to a nitrogen of
another amino acid
C O
H N
This type of interaction can occur with the chain
coils to form a spiral structure called - helix
130
Hydrogen bonding within a protein chain causes it to form a stable
helical structure called the alpha-Helix
This is found in
fibrous protein like
wool and hair giving
it the elasticity
131
•Tertiary: The overall shape of the protein
(determined by hydrogen-bonding, dipoledipole interactions, ionic bonds, covalent
bonds and London forces).
Summary of the Various Types of Interactions that Stabilize the Tertiary
Structure of a Protein: (a) Ionic, (b) Hydrogen Bonding, (c) Covalent, (d)
London
Dispersion, and (e) Dipole-Dipole
132
Summary of the Various Types of Interactions that
Stabilize the Tertiary Structure of a Protein:
(a) Ionic,
(b) Hydrogen Bonding,
(c) Covalent,
(d) London Dispersion, and
(e) Dipole-Dipole
133
Carbohydrates
Food source for most organisms and
structural material for plants.
Empirical formula = (CH2O)n
 Most carbohydrates such as starch and
cellulose are polymers of monosacharides or
simple sugar monomers
Monosaccharides (simple sugars) are
polyhydroxy ketones and aldehydes
 Pentoses (5-carbon atoms) - ribose, arabinose
 Hexoses (6-carbon atoms) - fructose, glucose
134
Some Important Monosaccharides
135
Chiral carbon atoms in fructose
• Molecules with nonsuperimposable
mirror images exhibit optical isomerism
• A carbon atom with different groups
bonded to it in a tetrahedral arrangement
always has a nonsuperimposable mirror
images which gives rise to a pair of
optical isomers
136
Tetrahedral Carbon
atom with four
different substituents
cannot have its
mirror image
superimposed
137
The Mirror Image Optical Isomers of
Glyceraldehyde
*
138
Chiral carbon
atom
Fructose
CH 2OH
C
O
H
H
*C
*C
H
*C
OH
HO
OH
CH 2OH
D-Fructose
139
There are 3 chiral
Carbon atoms
There are 23 isomers
That differ in the ability
To rotate light
Complex carbohydrates
Disaccharides (formed from 2
monosaccharides joined by a glycoside
linkage)
sucrose (glucose + fructose)
Polysaccharides (many monosaccharide
units)
starch, cellulose
140
Sucrose is a disaccharideformed from alpha-Dglucose and fructose
141
(a) The Polymer Amylose is a Major Component of Starch
and is Made Up of Alpha-D-Glucose Monomers
(b) The Polymer Cellulose, which Consists of Beta-DGlucose Monomers
142
Nucleic Acids
• Life is possible because each cell when it
divides can transmit the vital information
about how it works to the next generation
• The substance that stores and transmits
information is a polymer called
deoxyribonucleic acid (DNA)
• DNA together with other similar nucleic acids
called ribonucleic acids is responsible for
the synthesis of various proteins needed by
the cell to carry out its life functions
143
Nucleic Acids
• DNA (deoxyribonucleic acids):
stores and transmits genetic
information, responsible (with RNA)
for protein synthesis. (Molar mass =
several billion)
•RNA (ribonucleic acid): helps in
protein synthesis. (Molecular
weight = 20,000 to 40,000)
144
Monomers of nucleic acid
Nucleotides
1. Five-carbon sugar, deoxyribose in DNA and
ribose in RNA.
2. Nitrogen containing organic base
3. Phosphoric acid molecule, H3PO4
• The base and the sugar combine to form a unit
that in turn reacts with phosphoric acid to
create a nucleotide
• The nucleotides become connected through
condensation reaction that eliminate water to
give a polymer that contain a billion units.
145
The Organic Bases Found in DNA and RNA
146
The base and sugar combine to form a unit that
in turn reacts with phosphoric acid to create the
nucleotide, which is an ester
147
A Portion of a
typical nucleic
acid chain
148
Double helix formation
• According to Watson and Crick (Nobel prize
winners), CAN is composed of two strands (threads)
running in opposite directions that are bridged by
hydrogen bonds between specific pyrimidine groups
on one strand and purine group on the other
• The two strands are twisted into a double -helix
structure
• The strongest hydrogen bonds form between
adonine and thymine and between guanine and
cystosine. Thus; A-T or G-C bonding interactions
will take place
• The sequence of nucleotides on one strand of the
double helix determines the sequence of the other
• The sequence of the bases determines what
information is stored.
149
(a) The DNA double helix contains two sugar-phosphate
backbones, with the bases from the two strands hydrogen bonded
to each other; the complementarity of the (b) thymine-adenine and
(c) cytosine-guanine pairs
150
Genetic Code and Protein
Synthesis follows!!!!!!!!!!!
151