Chapter 22
Organic and Biochemical
Molecules
Chapter 22: Organic and Biochemical Molecules
22.1 Alkanes: Saturated Hydrocarbons
22.2 Alkenes and Alkynes
22.3 Aromatic Hydrocarbons
22.4 Hydrocarbon Derivatives
22.5 Polymers
22.6 Natural Polymers
Computer model of a globular protein
The Position of Carbon in the Periodic Table
“I am Carbon and I am Special”
1. I can form strong and short C-C bonds.
2. The C-C bond is short enough to allow sideways overlap of the
unused p orbitals, resulting in bonding. I gladly form carboncarbon double bonds, and I can even form carbon-carbon triple
bonds.
3. I have no problem bonding to other elements (H, O, N, S, etc.–
I love them all). Given where I am in the periodic table, I typically
form four bonds, except in carbon monoxide.
I Am Special -- Try Comparing Me to My Brother, Si
1. The C-C bond is much stronger than the Si-Si bond. (Atomic
size increases down the group: bonds between atoms become
longer and weaker.)
2. For me BE (C-C) ~ BE (C-O). For Si, BE (Si-O) >> BE (Si-Si).
With availability of oxygen in nature, Si will exist mostly with
Si-O bonds.
3. I have no d - orbitals to worry about. CH3-CH3 is stable while
SiH3-SiH3 is very susceptible to species with a pair of lone pairs
of electrons to donate into the vacant d orbitals.
You can spend your whole life learning about me!
Bond Energy
and the
Stability of
Carbon
Chains
I Can Amaze You With Diversity
Consider the number of compounds with the formula C4H8O.
These are called structural isomers–compounds with the same
chemical formulas, but different
ways of connecting the atoms
together to form different
functional groups, or different
compounds with completely
different chemical and physical
properties.
Chemical Diversity of Organic Compounds
Reactivity & Polarity of Bonds in Organic Compounds
C
C Bonds are nonpolar, no difference in the EN values of the
atoms. They are relatively short (200 pm).
Result: Unreactive
C H Bonds are nearly nonpolar and short (109 pm)
EN (C-H) = 2.5 – 2.1 = 0.4
Result: Unreactive
C O Bonds are highly polar, with the oxygen end very electron rich
EN (C-O) = 2.5 – 3.5 = 1.0
Result: Reactive
C Br Bonds are nearly nonpolar:
EN (C-Br) = 2.5 – 2.8 = 0.3
Result: Relatively unreactive
C S Bonds are exactly nonpolar:
EN (C-S) = 2.5 – 2.5 = 0.0
Result: Relatively unreactive
Even though the EN differences are small for Br & S with carbon, the
atoms are so large that their bonds to carbon are long, weak, and reactive.
Certain Parts of Me Make Me Behave in
Certain Predictable Ways
Functional Groups – atoms or specific groups of
atoms that impart given
characteristics.
The secret to learning organic chemistry.
As the periodic table is to inorganic chemistry, functional
groups are the easy way to learn organic chemistry.
A Polarized Marriage Does Not Last Very Long
“ I am no different. I am quite reactive at the sites (bonds)
that have the high polarity.”
Figure 22.1: C-H bonds in methane
Figure 22.2: (a) Lewis structure of ethane
( C2H6 ). (b) molecular structure of ethane
Figure 22.3: Structures of (a) propane
(b) butane
Alkanes
•
•
•
•
•
•
•
•
•
•
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
CH4
C2H6
CH3CH3
C3H8
CH3CH2CH3
C4H10 CH3CH2CH2CH3
C5H12 CH3CH2CH2CH2CH3
C6H14 CH3CH2CH2CH2CH2CH3
C7H16 CH3-(CH2)5-CH3
C8H18 CH3-(CH2)6-CH3
C9H20 CH3-(CH2)7-CH3
C10H22 CH3-(CH2)8-CH3
Table 22.1 (P1014) Selected properties of the First 10
Normal Alkanes
Number of
Molar
Melting Boiling structural
Name
Formula
Mass Point (oC) Point(oC) isomers
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C H
16
30
44
58
72
86
100
114
128
142
-182
-183
-187
-138
-130
-95
-91
-57
-54
-30
-162
-89
-42
0
36
68
98
126
151
174
1
1
1
2
3
5
9
18
35
75
Figure 22.4: (a) normal butane
(b) branched isomer
n-Butane
Isobutane
Pentane
n - Pentane
CH3-CH2-CH2-CH2-CH3
Isopentane
2-Methyl Butane
CH3-CH-CH2-CH3
CH3
Neopentane
2,2-Dimethyl Propane
CH3
CH3 – C – CH3
CH3
Boiling Points of Hydrocarbons
Rules for Naming Alkanes (P 1016-1017)-I
1) The names of the alkanes beyond butane are obtained by adding the
suffix –ane to the Greek root for the number of carbon atoms (pentfor five, hex- for six, and so on). For a branched hydrocarbon, the
longest continuous chain of carbon atoms determines the root name
for the hydrocarbon. For example in the alkane:
The longest chain contains 6 carbon atoms.
CH3
The compound is named hexane.
CH2 Longest Chain
6 carbons
CH2
CH3-CH2-CH-CH2-CH3
2) When alkane groups appear as substituents, they are named by droping
the –ane and adding –yl. For example, -CH3 is obtained by removing
a hydrogen from methane and is called methyl, -C2H5 is called ethyl,
-C3H7 is called propyl, and so on. The compound above is therefore
an ethylhexane. (see table 22.2)
Rules for Naming Alkanes (P 1016-1017)-II
3) The positions of aubstituent groups are specified by numbering the
longest chain of carbon atoms sequentially, starting at the end closest
to the branching. For example, the compound
CH3
CH3-CH2-CH-CH2-CH2-CH3
1
2
3 4
5
6
is called 3-methylhexane. Note that the set of numbers is correct
since the left end of the molecule is closest to the branching, and this
gives the smallest number for the position of the substituent. Note
that a hyphen is written between the number and the substituent
name.
4) The location and name of each substituent are followed by the root
alkane name. The substituents are listed in alphabetical order, and the
prefixes di-, tri-, and so on, are used to indicate multiple, identical
substituents.
Naming Saturated Hydrocarbons
Based on the longest chain of carbon atoms
Prefix + root + suffix
Location and nature of
substituents on chain
Class of organic compound
-ane for alkanes
Indicator of the # of C’s in the
longest chain
Numerical Roots for Carbon Chains and Branches
Root
methethpropbutpenthexheptaoctnondec-
Number of Carbon Atoms
1
2
3
4
5
6
7
8
9
10
Like Example 22.2 (P 1017-18)-I
Draw the structural isomers for the saturated hydrocarbon heptane C7H16 .
name each of the isomers.
Solution:
Straight chain: CH3-CH2-CH2-CH2-CH2-CH2-CH3
n-Heptane
One methyl group: CH3-CH-CH2-CH2-CH2-CH3
2-Methylhexane
CH3
3-Methylhexane
CH3-CH2-CH-CH2-CH2-CH3
CH3
Two methyl groups: CH3-CH-CH2-CH-CH3
CH3
CH3
2,4-dimethyl pentane
CH3
CH3-CH-CH-CH2-CH3
CH3-C-CH2-CH2-CH3
CH3 CH3
CH3
2,2-dimethylpentane
2,3-dimethylpentane
Like Example 22.2 (P 1017-18)-II
Two methyl groups cont.
CH3
CH3-CH2-C-CH2-CH3
CH3
CH3CH2-CH-CH2-CH3
CH2
CH3
2,2,3-trimethylbutane
3,3-dimethylpentane
3-ethylpentane
CH3
CH3-CH-C-CH3
CH3 CH3
Reactions of Alkanes - Chlorination
The Stepwise Chlorination of Methane by Chlorine:
CH4 (g) + Cl2 (g)
CH3Cl(g) + Cl2 (g)
CH3Cl(g) + HCl(g)
CH2Cl2 (g) + HCl(g)
CH2Cl2 (g) + Cl2 (g)
CHCl3 (g) + HCl(g)
CHCl3 (g) + Cl2 (g)
CCl4 (g) + HCl(g)
CH4 (g) + 4 Cl2 (g)
CCl4 (g) + 4 HCl(g)
Figure 22.5: (a) molecular structure of
cyclopropane (b) overlap of sp3 orbitals
Figure 22.6: (a) chair (b) boat forms
Figure 22.7: Bonding in ethylene
Figure 22.8: Bonding in ethane
Figure 22.9: The two stereoisomers
of 2-butene
Figure 22.10: Bonding in acetylene
Hydrocarbons
C + H
Compounds containing only carbon and hydrogen with only single
bonds and no multiple bonds
- Saturated hydrocarbons
- Alkanes
CnH2n+2
Compounds containing only carbon and hydrogen with only single
bonds and no multiple bonds, but a ring structure
- Saturated hydrocarbons
- Cycloalkanes CnH2n
Compounds containing only carbon and hydrogen with double bonds
- Unsaturated hydrocarbons
- Alkenes CnH2n
Compounds containing only carbon and hydrogen with triple bonds
- Unsaturated hydrocarbons
- Alkynes CnH2n–2
Conformations from rotation of single bonds–isomers exist as a result
of rearrangements of the atoms in different structural formulas.
Drawing Hydrocarbons–I
Problem: Draw structures for hydrocarbons that have different
structures with:
a) seven C atoms, no multiple bonds, and no rings.
b) five C atoms, one double bond, and no rings.
c) five C atoms, no multiple bonds, and one ring.
Plan: In each case, we draw the longest carbon chain and then work
down to smaller chains with branches at different points along
them. The process typically involves trial and error. Then we add
H atoms to give each C atom a total of four bonds.
Solution: (only the carbon backbone will be shown here)
a) compounds with seven C atoms: (9) [C7H16]
C
C-C-C-C-C-C-C
C-C-C-C-C-C C-C-C-C-C-C C-C-C-C-C
C
C
C
C
C-C-C-C-C
C
C-C-C-C-C C-C-C-C-C C-C-C-C-C
C-C-C-C
C
CC
C
C
C C
C
C
Drawing Hydrocarbons–II
b) compounds with 5 C atoms and one double bond: (5) [C5H10]
C=C-C-C-C
C=C-C-C
C=C-C-C
C
C-C=C-C
C
C
C-C=C-C-C
c) compounds with 5 C atoms and one ring: (5) [C5H10]
C
C-C-C
C
C-C-C-C
C
C-C-C-C
C
C-C-C
C-C
C-C
C
C
C
Naming and Drawing Alkanes, Alkenes,
and Alkynes–I
Problem: Give the systematic name for each of the following, indicate
the chiral center in part (d), and draw two geometric isomers for part (e).
(a)
CH3
(b)
CH2-CH3
CH3 - CH - CH-CH3
CH3-CH2-CH2-CH-CH-CH3
CH3
CH2
CH3
H2
(c)
CH3 CH3
H2
CH3
(d) CH3-CH2-CH-C-CH3
H2
H2
CH3
CH3
(e) CH3-CH2-CH=C-CH-CH3
CH2-CH3
CH3
Plan: For (a) to (c), we refer to Table 15.2. We first name the longest
chain (root- + -ane). Then we find the lowest branch numbers by counting
C atoms from the end closer to a branch. Finally, we name each branch
(root- + -yl) and put them alphabetically before the chain name.
Naming and Drawing Alkanes, Alkenes, and
Alkynes–II
Plan:Cont. For (e), the longest chain that includes the multiple bond is
numbered from the end closer to it. For (d), the chiral center is the C
atom bonded to four different groups. In (e), the cis isomer has larger
groups on the same side of the double bond, and the trans isomer has
them on opposite sides.
Solution:
CH2 - CH3
H
(a)
CH3
(b) CH3 - CH2 - CH2 - C - C - CH3
7
6
5
4 3
CH3 - CH - CH - CH3
2 CH2
1
2
3
4
CH3
2,3-Dimethylbutane
1
CH3
3-Methyl-4-ethylheptane
Naming and Drawing Alkanes, Alkenes, and Alkynes–III
(c)
H2
H2
(d)
3
CH3 CH3
CH3
CH3 - CH2 - C - C - CH3
5
H2
2
1
H2
CH2 - CH3
1-Ethyl-3-methylcyclohexane
4
3
chiral center
H
2
1
CH3
2,2,3-Trimethylpentane
(e)
H
CH3
CH3
CH3 - CH2 - C = C - CH - CH3
CH3 - CH2 - C = C - CH - CH3
CH3
cis-2,3-Dimethyl-3-hexene
H
CH3
trans-2,3-Dimethyl-3-hexene
Alkenes
Alkenes–Carbon compounds that contain at least one C=C double bond.
Alkenes have the general formula: CnH2n
Alkenes are called unsaturated hydrocarbons
The names of alkenes differ from those of alkanes in two respects:
1) The root chain must contain both C atoms of the double bond,
even if it is not the longest chain. The chain is numbered from
the end closer to the C=C bond, and the position of the bond is
indicated by the number of the first C atom in it.
2) The suffix for alkenes is -ene.
Examples: Ethylene, C2H4; Propene, C3H6; Butene, C4H8
H2C=CH2 H2C=CH-CH3 H3C-CH=CH2
Ethylene
Propylene = Propene
H2C=CH-CH2-CH3
1-Butene
H3C-CH=CH-CH3
2-Butene
H3C-CH2-CH=CH2
1-Butene
H2C=C-CH3
2-Methyl propene
CH3
Alkenes
C2H4
Ethylene
H2C=CH2
C3H6
Propylene
H2C=CH–CH3
C4H8
Butene
H2C=CH–CH2–CH3
C5H10 Pentene
H2C=CH–CH2–CH2–CH3
C6H12 Hexene H2C=CH–CH2–CH2–CH2–CH3
C7H14 Heptene
H2C=CH–( CH2)4–CH3
C8H16 Octene
H2C=CH–( CH2)5–CH3
The Initial Chemical Event in Vision
Alkynes
Alkynes –Hydrocarbons that contain at least one C C bond
Alkynes have the general formula: CnH2n–2
Alkynes are named the same way as alkenes, except that
the suffix is -yne.
Examples:
HC
CH
Acetylene
HC
C- CH2-CH3
1-Butyne
HC
HC
C-CH3
Propyne
H3C-C C-CH3
2-Butyne
C-CH2-CH2-CH3
1-Pentyne
H3C-C
CH
Propyne
H3C-CH2-C
CH
1-Butyne
H3C-C C-CH2-CH3
2-Pentyne
R-Group Names and Chemical Formulas
methyl
- CH3
ethyl
- CH2 - CH3 or - C2H5
n-propyl
- CH2 - CH2 - CH3
isopropyl
n-butyl
isobutyl
tert-butyl
H2
cyclopentyl H
- CH2 - CH2 - CH2 - CH3
H2
H2
or - C3H7
- CH - CH3
CH3
H2
cyclobutyl
or - C4H9
- CH2 - CH - CH3
CH3
CH3
H H2 cyclohexyl
- C - CH3
CH3 cyclopropyl H2
H2
H
H2
H2
H2
H2
H
H2
H2
H2
Figure 22.11: The structure of benzene
Figure 22.12: Some selected substituted
benzenes and their names
Compounds containing aromatic rings
are often used in dyes, such as these for
sale in a market in Nepal
Source: Getty Images
Some Reactions of Alcohols–I
1) The reaction of an alcohol with an alkali metal to form an alkoxide
ion:
As with water: 2 Na(s) + 2 H2O(l)
2 NaOH(aq) + H2 (g)
With alcohols a similar reaction occurs, forming an alkoxide ion:
2 Na(s) + 2 CH3-CH2-OH(l)
2 CH3-CH2-O-(aq) +2 Na+(aq) + H2 (g)
H2 (g) + 2 CH3-O-(aq) + 2 Li+(aq)
2 Li(s) + 2 CH3-OH(l)
2) Dehydration of alcohols yields an unsaturated compound–an
alkene or an ether (R-O-R). An example of the formation of an alkene:
OH
Phenol
H2SO4
+ H2O
Cyclohexene
Some Reactions of Alcohols–II
2) cont., Formation of an ether:
H2SO4
2 CH3-OH(l)
Methanol
CH3-CH2-OH
H(l) ++ HO-CH
HO- 2-CH3 (l)
Ethyl alcohol
H2SO4
Ethanol
CH3-CH2-CH2-CH2-CH2-CH2-OH(l)
n-Hexanol
CH3-O-CH3 (g) + H2O(l)
Dimethyl ether
H2O(l) + CH3-CH2-O-CH2-CH3
Diethyl ether
OH
+ CH3-CH-CH2-CH3 (l)
2-Butanol
CH3
H-C-O-CH2-CH2-CH2-CH2-CH2-CH3 (l)
CH2
2-Butyl n-hexyl ether
CH3
H2SO4
Some Reactions of Alcohols–III
3) Oxidation - Yields an aldehyde, acid or, for some alcohols, a ketone.
Primary alcohols
Aldehyde
Secondary alcohols
Ketone
Tertiary alcohols
CH3-CH2-OH(l)
Ethanol
[O]
-H2O
OH
CH3-CH-CH2-CH3 (l)
2-Butanol
Organic Acid
no oxidation
K2Cr2O7 = [O] = “Oxidation”
H2SO4
O
O
[O]
CH3-C-H
CH3-C-OH
-H2O
Ethanal
Acetic acid
[O]
-H2O
O
CH3-C-CH2-CH3 (l)
Ethyl methyl ketone
Ethanol is being tested in selected areas
as a fuel for automobiles
Source: AP/Wide World Photos
Some Molecules with Alcohol Functional Group
Cinnamaldehyde produces the
characteristic odor of cinnamon
Source: Visuals Unlimited
Aldehydes
O
Formaldehyde
Methanal
H C
H
Acetaldehyde
Ethanal
O
H3C
CH
C
CH
CH
CH
H
O
CH
Benzaldehyde
C
C
H
Ketones
O
Dimethyl ketone
Acetone
H3C
C
O
Ethyl methyl ketone
H3C
Diethyl ketone
H3C
CH3
CH2
C
CH3
O
CH2
C
CH2
CH3
Some Common Aldehydes and Ketones
Figure 22.13: Some common ketones
and akdehydes
The
Carbonyl
Group
Carboxylic Acids
O
Formic acid
H
C
O H
H3C
Propionic acid
O
Acetic acid
C
O
H
O
H3C
CH2
C
O
H
O
H3C
CH2
CH2
C
Butanoic acid
O H
Figure 22.14: Some carboxylic acids
Some Molecules with the Carboxylic
Acid Functional Group
Which Reactant Contributes Which
Group to the Ester?
Isotopic labeling shows that the oxygen atom in the ester comes
from the alcohol, not the acid, and that the oxygen found in the
water formed as a byproduct comes from the acid.
Alcohol + Organic Acids
Ethyl alcohol + Acetic acid
O
Ethanol
H3C
CH2 OH + H3C
Ethyl acetate
H3C
CH2
O
C
O
C
Esters–I
=
Ethyl acetate
Acetic acid
O H
Water
CH3 + H2O
Alcohol + Organic acid
Esters–II
Methyl alcohol + Formic acid = Methyl formate
O
H3C O
H+H O C
O
H
H3C O C
H + H2O
Methyl alcohol + Butyric acid = Methyl butyrate
O
H3C
O H + H 3C
H2O +
H3C
CH2
CH2
CH2
CH2
O
C
C
O
O H
CH3
Alcohol + Organic acid
Esters–III
O
Methyl formate
H
C O
CH3
O
H3C
C
O
Methyl acetate
CH3
O
H3C
Ethyl acetate
C
O
CH2
CH3
O
H3C
CH2
CH2
C
O
CH2 CH3
Ethyl butyrate
Pineapples
Some Lipid Molecules with the Ester
Functional Group
Esters are the Flavoring in Fruits–I
Benzyl acetate C9H10O2 –oil of jasmine
Isoamyl acetate C7H14O2–ripe apples
O
CH3-C-O-CH2-
O
CH3
CH3-C-O-CH2-CH2-CH-CH3
Ethyl 2-methylbutanoate C7H14O2–ripe apples
CH3 O
CH3-CH2-CH-C-O-CH2-CH3
Isoamyl acetate C7H14O2–bananas
O
CH3
CH3-C-O-CH2-CH2-CH-CH3
Ethyl butyrate C6H12O2–pineapple
O
CH3-CH2-CH2-C-O-CH2-CH3
Ethyl formate C3H6O2–rum
O
H-C-O-CH2-CH3
Esters are the Flavoring in Fruits–II
Amyl butyrate C9H18O2–apricot
O
CH3-CH2-CH2-C-O-CH2-CH2-CH2-CH2-CH3
Ethyl formate C3H6O2–lemonade
O
H-C-CH2-CH3
n-Octyl acetate C10H20O2–oranges
O
CH3-C-O-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
Methyl salicylate C8H8O3–oil of wintergreen
O
C-O-CH3
OH
Computer-generated space-filling
model of acetylsalicylic acid (aspirin)
Source: Photo Researchers, Inc.
Amines–I
..
N
NH3 Ammonia
CH3NH2
H
H
H
Methyl amine
..
N
(CH3)2NH
Dimethyl amine
CH3
H
H
(CH3)3N
Trimethyl amine
..
..
N
N
CH3
CH3
CH3
CH3
H
CH3
Figure 22.15: The general formulas for primary,
secondary, and tertiary amines:
Amines–II
CH3-CH2-NH2
Ethyl amine
CH3-CH2-CH2-NH2
n-Propyl amine
CH3-CH2-CH2-CH2-NH2
n-Butyl amine
CH
CH
C
NH2
Phenyl amine
CH
CH
CH
Soybeans
Source: AP/Wide World Photos
Benzoyl Peroxide
O
O
O
O
Heat
A “free radical” is a
molecule with an
unpaired electron.
O
2
O.
Polymerization of Ethylene–I
Benzoyl peroxide
radical
O
Ethylene
+
O.
H2 C
O
CH2
O
Adduct
CH2
.
CH2
Polymerization of Ethylene–II
O
+
CH2
O
2
H2C
CH2
CH2
.
O
CH2
O
CH2
CH2
CH2
CH2
CH2
.
Structures and Applications of Some Major Addition
Polymers (Based upon the Ethylene Molecule)–I
Monomer
H
Polymer
H
C
C
Polyethylene
H
H
F
F
C
C
F
F
H
H
C
C
H
CH3
H
H
C
H
Applications
C
Cl
Plastic bags, bottles, toys
Polytetrafluoroethylene
Polypropylene
Cooking utensils
(e.g. Teflon)
Carpeting (indoor-outdoor),
bottles
Poly(vinyl chloride) Plastic wrap, garden hose,
indoor plumbing
Structures and Applications of Some Major Addition
Polymers (Based upon the Ethylene Molecule)–II
Monomer
H
Polymer
H
C
H
Phenyl
H
H
C
C
H
H
N
C
H
O
H
Cl
C
Polyacrylonitrile
C
H
C
O
C
Cl
H
CH3
H
C
C
CH
O
Insulation, furniture
Yarns, fabrics, wigs,
(e.g. Orlon, Acrilon)
Poly(vinyl acetate) Adhesives, paints, textile
coatings, computer disks
Poly(vinylidene chloride)
C
H
C
Polystyrene
C
Applications
Food wrap (e.g. Saran)
Poly(methyl methacrylate) Glass substitute (e.g.
Lucite, Plexiglas),
CH3
bowling balls, paint
Poly(Vinyl Chloride) (PVC) and Teflon
H
C
H
H
C
Cl
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
H
Cl
H
Cl
H
Cl
H
Cl
Vinyl chloride
F
F
C
n
PVC
F
C
H
F
F
F
F
F
F
F
F
C
C
C
C
C
C
C
C
F
F
F
F
F
F
F
F
F
Tetrafluoroethylene
Teflon
n
Styrene
H
Polystyrene
H
C
C
H
H
H
H
H H
H
H H
H
C
C
C
C
C
C
C
H
H
C
H
H
C
H
n
Figure 22.17: Major use of HDPE is for
blow-molded objects such as bottle for soft
drinks, shampoos, bleaches, and so on
Important Polymer Linkage Groups
• Linkage
-COO-
-CONH-
-C-O-C-
• Name
Ester
Amide
Ether
• Precursors
•
Acid +
Alcohol
Acid +
Amine
Alcohol +
Alcohol
• Polymer
• Type
•
Polyesters Polyamides Cellulose
•
Proteins
Starch
Nylon netting magnified 62 times
Source: Corbis
Colored water drops are shown beading on
Kevlar fabric treated with a non-scale
water-resistant coating.
Source: AP/Wide World Photos
O
Condensation Polymers
Polyamides–Nylon-66
OH
HO
Adipic acid
+
O
NH2
H2N
Hexamethylenediamine
H
O
N
N
O
H n
The formation
of nylon - 66
Figure 22.16: The reaction to form nylon can
be carried out at the interface of two
immiscible liquid layers in a beaker
Wallace H. Carothers
Source: Dupont - Wilmington, Delaware
Two Molecules with the Same Functional
Group at Both Ends of Each Molecule–
Two Different Monomers
Nylon-66
Adipic acid and
Hexamethylenediamine
Kevlar
Terephthalic acid and
Phenylenediamine
Polyesters
Terephthalic acid and
Ethylene glycol
Kevlar
O
HO
H2N
C
+
C OH
Terphthalic Acid
NH2
Phenylenediamine
O
O
HO
C
H
N
+
C
O
E TC
NH2
H2O
Polyesters ( PET )
Polyethylene Terphthalate
O
C
HO
OH
+
HO
H
H
C
C
OH
H
H
Ethylene Glycol
C
Terphthalic acid
O
O
C
CH2
O
CH2
+
O
C
O
n
H2O
O
Polyurethane
C
N
H3C
H Glycerol
Toluene diisocyanate
N C O
H C O H
+
H C O H
H C O H
H
O
C
H
N
O
H3C
N
C
Polymer
O
H
O H
C
C
C
H H
H
O H
Plastic Recycling–I
1) PET Polyethyleneterephthalate
Soft drink bottles, blister packs, photographic film, oven proof trays,
fiberfill (Dacron)
2) HDPE
High density polyethylene
Milk jugs, many types of containers (food, liquid detergent,
shampoos, etc.)
3) PVC
Poly(vinyl chloride)
“Synthetic leather” upholstery, water pipes, house siding, flooring,
bottles for cooking oils, shrink wrap, meat & poultry wrap, garden
hoses, phonographic records, laboratory tubing
4)
LDPE Low density polyethylene
Films (food wrappings, plastic bags, etc.), flexible containers such
as squeeze bottles for mustard, etc.
Plastic Recycling–II
5)
PP Polypropylene
Appliances, autos, pipe, drinking straws, bottle caps,
luggage, bread and cheese wrap, cereal box liners,
wrap for clothing
6) PS
Polystyrene
Styrofoam, hot-drink cups, plastic plates & silverware,
egg cartons, food trays, and fast food containers
7) Other plastics–addition polymers
Teflon
Lucite, plexiglass
Poly(vinyl acetate)
Natural rubber
Neoprene rubber
Styrene butadiene rubber
A scanning electron microscope image
showing the fractured plane of a self-healing
material with a ruptured microcapsule in a
thermosetting matrix
Source: University of Illinois Urbana-Champaign
Macromolecules in Living Organisms
Nucleic Acids
Carbohydrates
Proteins - The molecular machinery of the cell
* Polyamides made from the condensation reactions of
amino acids. Each amino acid contains a carboxyl group at
one end and an amino group at the other end.
* Nine amino acids have nonpolar character and are found
inside of proteins.
* Eleven amino acids have polar side chains, are more polar,
and found on the outside of a protein where they may be in
contact with water.
Figure 22.18: The 20 α-amino acids found in most
proteins. [ Nonpolar R Groups ]
Figure 22.18: The 20 α-amino acids found in
most proteins. [ Nonpolar R Groups ] (cont’d)
Figure 22.18: The 20 α-amino acids found in
most proteins. [ Polar R Groups ]
Figure 22.18: The 20 α-amino acids found in
most proteins. [ Polar R Groups ]
Figure 22.18: The 20 α-amino acids found in most
proteins. [ Polar R Groups ]
Figure 22.18: Alpha-amino acids, Polar R groups (continued).
Amino Acids–The Building Blocks of Proteins
In general, amino acids have the form:
R O
H2 N - C - C - O - H
H
Amino acids are normally charged, because the carboxyl group
transfers an H+ ion to H2O to form H3O+, which transfers the H+
to the amine group.
- H2O
H3O+
R O
H2N - C - C - O - H
H
+ H2O
R O
H3N+- C - C - O H
Polypeptides
• A macromolecule made up of amino acids;
• All proteins are polypeptides;
• A small protein (polypeptide) consists of 50-100
amino acids;
• A large protein may contain up to thousands;
myosin, a muscle protein, has approximately 1750
amino acids.
Tripeptide containing glycine, cysteine,
and alanine
Source: Photo Researchers, Inc.
Figure 22.19: The amino acid sequences
in (a) oxytocin and (b) vasopressin
Figure 22.20: Hydrogen
bonding within a
protein chain
Figure 22.21:
Ball-and-stick
model of a portion
of a protein chain
Figure 22.22: Hydrogen bonding
Figure 22.23: (a) collagen (b) pleated sheet
arrangement of many proteins bound together to from
the elongated protein found in silk fibers
Figure 22.24: Protein myoglobin
Figure 22.25: Summary of the various types
of interactions that stabilize the tertiary
structure of protein
Figure 22.26: Permanent waving of hair
Figure 22.27: Schematic representation
of the thermal denaturation of a protein
Carbohydrates
• General formula = Cx(H2O)y
• Carbohydrates are an important food
source for organisms.
• Some important ones are:
– Glucose C6H12O6
– Fructose C6H12O6
– Sucrose C12H22O11
• Oligosaccharides - Disaccharides
– Two simple sugars (monosaccharides) linked
together
• Polysaccharides–biopolymers
– Starch–cellulose
Figure 22.28: Tetrahedral carbon
atom has four different substituents
Self-tanning products
Figure 22.29: The mirror image optical
isomers of glyceraldehyde
Figure 22.30: The cyclization of D-fructose
Figure 22.31: The cyclization of glucose
Figure 22.32: Sucrose is a disaccharide formed
from α-D-glucose and fructose
Polysaccharides
• Glycogen–produced in the livers of animals
– ~1000 Monomers
– Many branches on the main chain, but their average
length is less than 30 monomer units
– Branches are fairly frequent with them occurring every
8-12 monmer units
• Starch–produced in plants
– Glucose polymers: amylose and amylopectin
• Cellulose–produced in plants
– ~ 2000-3000 Glucose units long, but glucose units are
combined as cellobiose units which have a beta linkage
Figure 22.33: Polymers amylose and cellulose
Amylose - a
Cellulose - b
A Portion of the Structure of Glycogen, the
Major Storage Polysaccharide in Animals
3 Important Building Blocks
of Nucleic Acids
• 1) A pentose sugar–In RNA the sugar is ribose,
and in DNA it is deoxyribose, in which one
hydroxy group has been replaced by a hydrogen.
• 2) A nitrogen containing organic base:
– Adenine
– Guanine
– Thymine
– Cytosine
– Uracil
• 3) A phosphate linkage derived from phosphoric
acid
Figure 22.34: Pentoses
DNA
RNA
Figure 22.35:
The organic
bases found in
DNA/RNA
Figure 22.36: Adenosine reaction
Figure 22.37:
Nucleic acid chain
Figure 22.38: DNA double helix
Prize-Winning Work on
Nucleic Acids and DNA
• 1940’s British chemist Alexander Todd–
(Nobel Prize)
– Discovered the basic composition of DNA.
• 1950’s Edwin Chargaff (Columbia Univ.)
– Found that different species had different numbers of bases.
– Found that the molar ratio of guanine to cytosine and adenine
to thymine was always very close to 1.0, suggesting that
somehow, adenine and thymine are paired in DNA and so are
guanine and cytosine.
• 1953 James D. Watson , Francis Crick and
Maurice Wilkins–Nobel Prize
– Found the double helix structure of DNA.
Figure 22.39:
Cell division of DNA
Figure 22.40: mRNA molecule
Four of the Functional Groups
Alcohol group - Hydroxyl group
C
..
O
..
Ether group
H
..
O
..
C
Alcohol
C
Ether
Carboxylic acid group
..
O
C
Ester group
..
..
O
..
Carboxyl
O
H
C
..
..O
Ester
C
More Functional Groups
Alkenes
Alkynes
Thiols and Disulfides
Amines (primary, secondary, tertiary)
Aldehydes
Ketones
Amides
Suggested
“Must Learn Items”
Important Functional Groups in Organic Compounds-I
Functional Group
Compound Type
Suffix or Prefix of
name
Example
Systematic Name
(Common Name)
H
C
alkene
C
H
-ene
C
H
C
C
..
..O
C
C
O
C
C
..
N
H
C
..
..X
alkyne
-yne
alcohol
ether
-ol
H
H
H
H
C
C
..
..O
H
H
haloalkane
amine
halo-amine
H
C
C
C
ethyne
(acetylene)
H
H
H
H
ether
ethene
(ethelene)
C
methanol
(methyl alcohol)
H
O
H
C
H
H
chloromethane
(methyl chloride)
Cl
H
H
H
H
C
C
H
H
..
N
H
dimethyl ether
H
ethylamine
Important Functional Groups in Organic Compounds - II
Functional Group
Compound Type
Suffix or Prefix of Example
Name
H O
Systematic Name
(Common Name)
aldehyde
-al
ethanal
(acetaldehyde)
O
C H
O
C
C
C
ketone
H
C
H
-one
O
..
C O
..
O
C
O
C
..O
..
..
N
C
carboxylic acid
H
C
ester
amide
H
H
O
H
H
C
C
C
H
O
C
C
-oic acid H
-oate
C
..HO
..
H
C
C
H
H
O
C
C
nitrile
H
-nitrile
H
C
H
H
C
N
....O
H
C
H
..N
H
2-propane
(acetone)
ethanoic acid
(acedic acid)
H
O
H
N
H
H H
-amide
H
H
methyl ethanoate
(methyl acetate
ethanamide
H (acetamide)
ethanenitrile
(acetonitrile,
methyl cyanide)
Some Five-Carbon Skeletons
saturated carbon cpds.
one double bond
one simple ring
Adding the H-Atom Skin to the C-Atom Skeleton
Xylenes–The Three Isomers of C8H10
CH3
CH3
CH3
CH3
CH3
CH3
1,2-Dimethylbenzene
(o-xylene)
bp = 144.4°C
1,3-Dimethylbenzene
(m-xylene)
bp = 139.1°C
1,4-Dimethylbenzene
(p-xylene)
bp = 138.3°C
TNT and its Decomposition (Explosion!)
CH3
O2 N
NO2
2,4,6-Trinitromethylbenzene
(trinitrotoluene, TNT)
C7H5N3O6
NO2
4 C7H5N3O6 (s) + 33 O2 (g)
28 CO2 (g) + 10 H2O(g) + 12 NO2 (g) + Energy
Naphthalene and Benzo[a]pyrene
Aromatic Carcinogens
Napthelene
C10H8
Benzo[a]pyrene
C20H12
(P 621)
Isomers
Structural
Stereoisomers
Geometric
Optical
Optical Isomerism and Chiral Molecules
Stereoisomerism: Molecules with the same sequence of atoms,
but different orientations of groups in space.
Optical isomerism: A type of stereoiosmerism that occurs when
an object and its mirror image cannot be
superimposed on each other.
Chiral: An asymmetric organic molecule that contains at least one
carbon atom that is bonded to four different groups.
An
Analogy for
Optical
Isomers
Optical Isomers
B and C do not superimpose
Consider carbon bonded to A, B, C, and D.
There are two possible structures.
AA
The two structures are mirror
images of each other. They
are optical isomers of each other.
BC
DD
CB
Each of the two forms is asymmetric - no
plane of symmetry. An organic molecule is
chiral if it has a carbon atom that is bonded
to four different groups.
The Rotation of Plane-Polarized Light by
an Optically Active Substance
Some Reactions of Alcohols–IV
4) Substitution reaction of an alcohol with hydrohalic acids to form
haloalkanes and water:
General formula:
R-OH + HX
R-X + H2O
Examples:
CH3-OH(l) + HCl(aq)
CH3-Cl(g) + H2O(l)
CH3-CH2-CH2-OH(l) + HI(aq)
5) Esterification:
Alcohol + Organic Acid = Ester + Water
O
CH3-OH(l) + HC-OH
Methanol
CH3-CH2-CH2-I(l) + H2O(l)
[H+]
Formic acid
CH3-CH2-OH(l)
Ethanol
O
[H+]
+ CH3-C-OH(l)
Ethanoic acid
O
H-C-O-CH3 (l)
Methyl formate
O
CH3- C-O-CH2-CH3 (l)
Ethyl ethanoate
Optical Isomerism
How different are optical isomers? They have the exact same chemical
formula, chemical and physical properties, but they are different in two
ways:
1) They rotate the plane of polarized light (Fig 15.11):
rotation to the right
detrorotatory ( d or + )
rotation to the left
levorotatory ( l or - )
2) In their chemical properties, optical isomers differ only in a chiral
environment.
dform of A + dform of B
product.
dform of A + lform of B
no reaction.
Example: Of d-glucose and l-glucose, only d-glucose is metabolized
in humans–a good example of the important selectivity of life forms.
The Binding Site of an Enzyme
The Basis of Proton Spin Resonance
Fig. 15.B (p. 622)
The 1H-NMR Spectrum of Acetone
Fig. 15.C (p. 623)
1H-NMR
Spectrum of Dimethoxymethane
Fig. 15.D (p. 623)
Fig 15.E
MRI of
the
Human
Brain
(P 623)
R-Group Names and Chemical Formulas
methyl
- CH3
ethyl
- CH2 - CH3 or - C2H5
n-propyl
- CH2 - CH2 - CH3
isopropyl
n-butyl
isobutyl
tert-butyl
H2
cyclopentyl H
- CH2 - CH2 - CH2 - CH3
H2
H2
or - C3H7
- CH - CH3
CH3
H2
cyclobutyl
or - C4H9
- CH2 - CH - CH3
CH3
CH3
H H2 cyclohexyl
- C - CH3
CH3 cyclopropyl H2
H2
H
H2
H2
H2
H2
H
H2
H2
H2
Types of Organic Reactions–I
1) Addition Reactions: These reactions occur when an unsaturated
compound containing a double or triple bond becomes
saturated by adding a compound. This reaction occurs
for C=O, C=C and C=C bonds.
X Y
General form: R-CH=CH-R + X-Y
R-C-C-R
H H
Examples:
CH3-CH=CH-CH3 + H2
CH3-CH2-CH2-CH3
H-CH=CH-CH2-CH3 + Br2
Br Br
H-C-C-CH2-CH3
H H
H2C=CH2 + HCl
H Cl
H-C-C-H
H H
A Color Test for the C=C Bonds
Fig. 15.14 (P 624)
Types of Organic Reactions–II
2) Elimination Reactions: These are the opposite of addition reactions.
A saturated reactant becomes an unsaturated
compound, and another molecule is formed.
X Y
General form: R-CH-CH2
R-CH=CH2 + X-Y
Examples:
OH H
CH3-CH-CH2
OH
CH3-CH2-CH-CH3
Cl H
CH3-CH-CH-CH2-CH3
H2SO4
Cr2O72H2SO4
CH3-CH=CH2 + H2O
O
CH3-CH2-C-CH3 + H2O
CH3-CH=CH-CH2-CH3 + HCl
Types of Organic Reactions–III
3) Substitution Reactions: These reaction occur when an atom (or
group) from an added reagent substitutes
for one in the organic reactant.
General form: R-C-X + Y
Examples:
CH3-OH + HBr
O
CH3
CH3-C-Cl + CH3-CH-CH2-CH2-OH
CH3-CH2-CH2-Br + NaOH
CH3-CH2-CH2-Br + CH3-CH2-ONa
R-C-Y + X
CH3-Br + H2O
HCl + O
CH3
CH3-C-O-CH2-CH2-CH-CH3
CH3-CH2-CH2-OH + NaBr
NaBr +
CH3-CH2-CH2-O-CH2-CH3
Recognizing the Type of Organic Reaction
Problem: State whether each of the following reactions is an addition,
elimination, or substitution reaction:
a) CH3-CH2-OH + CH3-OH
CH3-CH2-O-CH3 + H2O
b) CH3-CH2-CH=CH-CH3 + H2
CH3-CH2-CH2-CH2-CH3
c) CH3-CH2-CH2-CH2-Cl
CH3-CH2-CH=CH2 + HCl
Plan: We determine the type of reaction by examining the change in the
number of atoms bonded to carbon.
a) More atoms bonded to carbon is an addition.
b) Fewer atoms bonded to carbon is an elimination.
c) Same number of atoms bonded to carbon is a substitution.
Solution: a) Substitution–the C-OH in both reactant molecules is
converted into C-O bonds in the product molecule, so the same
number of atoms are bonded to carbon.
b) Addition–two C-H bonds form in the product, so more atoms are
bonded to carbon.
c) Elimination–two bonds in the reactant (C-H,C-Cl) are not in the
The Redox Process in Organic Reactions
Oxidation numbers are not relied upon as much in organic reactions.
Instead, organic chemists note the movement of electron density
around the carbon atom by counting the number of bonds to more
electronegative atoms (normally oxygen) or to less electronegative
atoms (normally H).
An oxidation-reduction (redox) reaction involves both oxidation and
reduction, but organic chemists normally focus on the organic
reactant only. Therefore:
When a C atom in the organic reactant forms more bonds to O or
fewer bonds to H, the reactant is oxidized and the reaction is an
oxidation.
When a C atom in the organic reactant forms fewer bonds to O or
more bonds to H, the reactant is reduced and the reaction is a
reduction.
Organic Oxidation and Reduction Reactions
An example of an organic reaction that involves oxidation-reduction
is the reaction that occurs with ethanol and acidic potassium dichromate
to yield acetic acid:
O
CH3-CH2-OH
K2Cr2O7 (acid)
CH3-C-OH
In ethanol the C-2 has 2 bonds to hydrogen, and 1 bond to oxygen,
whereas in the product (acetic acid) C-2 has three bonds to oxygen and
no bonds to hydrogen. Thus, in this reaction the ethanol is oxidized to
form acetic acid, so this reaction is an oxidation.
Another reaction is the addition of hydrogen to the double bond in
propylene to form propane:
Pd
CH3-CH=CH2 + H2
CH3-CH2-CH3
Note that the C-2 and C-3 have more bonds to hydrogen than in the
reactant propylene, so this the reactant is reduced , and the reaction is
a reduction.
Alcohols
CH3OH
Methyl alcohol-Methanol
C2H5OH
Ethyl alcohol-Ethanol
C3H7OH
Propyl alcohol-Propanol
H3C CH2 CH2
n-Propyl alcohol
OH
H3C
CH3CH2OH
CH
OH
CH3
H3C
CH2
CH2
n-Butyl alcohol
CH2
OH
2-Propyl alcohol
Ethers
Dimethyl ether
H3C–O–CH3
Ethyl methyl ether H3C–O–CH2–CH3
Diethyl ether
H3C–CH2–O–CH2–CH3
CH
CH
Diphenyl ether
CH
C
CH
CH
CH
O
C
CH
CH
CH
CH
Reactions of Alkyl Halides with Anions
CH3-CH2-CH2Cl + NaCN
1-Chloropropane
CH3-CH2I + NaO-CH3
1-Iodoethane
CH3-CH2-Br + NaSH
Bromoethane
CH3-CH2-Cl + NaNH2
Chloroethane
CH3-CH2-CH2-CH2-Br + NaOH
1 - Bromobutane
CH3-CH2-CH2CN + NaCl
1-Cyanopropane
CH3-CH2-O-CH3
Methylethyl ether
CH3-CH2-S-H + NaBr
Ethylmercapton
CH3-CH2-NH2 + NaCl
Ethylamine
CH3-CH2-CH2-CH2-OH + NaBr
1-Butanol
1-Butyl alcohol
Polychlorinated Biphenyls (PCBs)
..
Cl
..
..
..
..
Cl
..
PCBs
..
Cl
..
..
..
..
Cl
..
Until recently, halogenated aromatics were used as insulating fluids
in electrical transformers and were discharged in waste water. Because
of their low solubility, they accumulated for decades in river and lake
sediment and were eaten by microbes and invertebrates. Fish ate the
invertebrates, and birds and mammals, including humans, ate the fish.
PCBs become increasingly concentrated in body fat at each stage. As a
result of their health risks, PCBs in natural waters present a real problem.
Some Biomolecules with the Amine
Functional Group
General Structures of Amines
Reactions of Alcohols, Alkyl Halides and Amines
Problem: Determine the reaction type and predict the products of the
following chemical reactions:
Cr2O7-2
( a) CH3-CH2-CH2-OH H SO
2
4
(b) CH3-CH2-Br + KOH
(c) CH3-CH2-OH + CH3-OH H2SO4
Plan: We examine the reactant(s) and other reagent(s) to decide on the
possibilities for each functional group, keeping in mind that, in general,
one functional group changes into another.
Solution:
O
CH3-CH2-C-OH Propanoic acid
(a) Elimination (oxidation):
(b) Substitution:
CH3-CH2-OH + KBr
(c) Elimination:
CH3-CH2-O-CH3
Ethyl alcohol
Methylethyl ether
Hydrolysis-Saponification
The Reverse Reaction of Ester Formation
Animal fats and/or vegetable fats which are “triglycerides” were broken
down using a strong base such as lye (NaOH) to produce a “soap”.
O
R- C-O-CH2
O
R’-C-O-CH + 3 NaOH
O
R”-C-O-CH2
A triglyceride
O
R-C-O- Na+
O
R-C-O- Na+
O
R-C-O- Na+
3 Soap
molecules
HO-CH2
+ HO-CH
HO-CH2
Glycerol
Amides
Formation of amides: Amides may be formed by the reaction between
an organic acid or ester and amine in a dehydration-condensation
reaction.
General formation:
O
H
R-C-OH + H-N-R’
OH
R-C-N-R’ + H2O
Examples: O
H
OH
CH3-CH2-C-OH + H-N-CH3
CH3-CH2-C-N-CH3 + H2O
Propionic acid
Methyl amine
N-Methylpropylamide
O
CH3
O CH3
CH3-CH2-CH2-C-OH + H-N-CH2-CH3 CH3-CH2-CH2-C-N-CH2-CH3
Butanoic acid
Methylethylamine N-Ethyl-N-methylbutanamide
O
CH3-C-O-CH3 + H2N-CH2-CH3
OH
CH3-C-N-CH2-CH3 + CH3-OH
Methyl ethanoate + Ethylamine
N-Ethylethanamide + Methanol
Some Molecules with the Amide
Functional Group
The Formation of Anhydrides
Image to come.
Rules for Naming an Organic Compound–I
1. Naming the longest chain (root)
(a) Find the longest continuous chain of carbon atoms.
(b) Select the root that corresponds to the number of carbon atoms
in this chain.
2. Naming the compound type (suffix)
(a) For alkanes, add the suffix -ane to the chain root. (Other suffixes
appear in Table 15.5 with their functional group and compound
type.)
(b) If the chain forms a ring, the name is preceded by cyclo-.
3. Naming the branches (prefix)
(a) Each branch name consists of a subroot (number of C atoms) and
the ending -yl to signify that it is not part of the main chain.
(b) Branch names precede the chain name. When two or more
branches are present, name them in alphabetical order.
Rules for Naming an Organic Compound-II
3.
continued:
(c) To specify where the branch occurs along the chain, number the
main-chain C atoms consecutively, starting at the end closer to
a branch, to achieve the lowest numbers for the branches. Precede
each branch name with the number of the chain C atom to which
that branch is attached.
(d) If the compound has no branches, the name consists of the root
and suffix.
6 carbons
hexhex- + -ane = hexane
CH3 methyl
1
CH3
2
3
CH
CH
4
CH2
CH2
CH3
ethyl
5
CH3
6
CH3
ethylmethylhexane
3-ethyl-2-methylhexane
Condensed vs. Expanded Formulas
Look at the formulas of 3-ethyl-2-methylpentane:
H
H
C
H
H
C
C
H
H
H
H
Expanded
Formula
CH3
H
H
H
H
C
C
C
H
C
H
H
C
H
H
CH3
H
CH
CH
CH2
CH2
CH3
Condensed Formula
CH3
Structure
of a
Cationic
Detergent