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The Chemistry of Life:
Organic and Biological
Chemistry
BLB 11th Chapter 25
25.1 General Characteristics

Structure
– Carbon atoms form 4 bonds.
– Backbone consists of –C—C— chains or rings.
– C—H bond is nearly nonpolar.

Stabilities
– C forms strong bonds with other elements.
– Alkanes are stable (unreactive).
– Functional groups (sect. 5) change reactivity.
General Characteristics

Solubility and acid-base properties
– Hydrocarbons: nonpolar, neutral
soluble in water? ______
– C—H (hydrocarbons) plus functional groups…
 -C—O—H polar, slightly acidic (alcohols)
 -C—O—O—H acidic (carboxylic acids)
 -C—N—R3 basic (amines)
– Surfactants combine both properties
25.2 Hydrocarbons
Compounds containing only C and H
 Types:

– Alkanes (saturated) – single C–C bonds
– Alkenes (unsaturated) – double C=C bonds
– Alkynes (unsaturated) – triple C≡C bonds
– Aromatic – alternating single and double bonds
25.3 Alkanes (CnH2n+2)

Variations
– Unbranched (normal, “straight-chained”)
– Branched
– Cyclic

Structural isomers – same number and
type of atoms but different bonding
arrangements
3-D Arrangement
Tetrahedral geometry
Name
Formula
MM
m.p. (°C)
b.p. (°C)
# isomers
methane
CH4
16
-183
-161
1
ethane
C2H6
30
-183
-89
1
propane
C3H8
44
-187
-44
1
butane
C4H10
58
-138
-0.5
2
pentane
C5H12
72
-130
36
3
hexane
C6H14
86
-95
68
5
heptane
C7H16
100
-91
98
9
octane
C8H18
114
-57
125
18
nonane
C9H20
128
-54
151
35
decane
C10H22
142
-30
175
75
Butane Isomers
Pentane Isomers
Nomenclature
1.
2.
3.
4.
Identify longest C chain → base name
Number C atoms – lowest number
nearest substituent
Give position and name substituents.
More than one substituent?
 Alphabetical
 Prefixes
 Some substituents have common names
(Table 25.2, p. 1059)
Structure & Nomenclature Examples
Structure & Nomenclature Examples
Structure & Nomenclature Examples
Cycloalkanes (CnH2n)
most stable
stable
structure
structure
strained & unstable
Alkenes & Alkynes

Alkenes: C=C double bonds
– Named similarly with an –ene ending and give
position of double bond
– More reactive than alkanes
– Different arrangements of substituents may result in
geometric isomers.

Geometric isomers – same atoms, same bonds,
but different spatial arrangement of substituent
groups.
– cis- and trans-
Structural isomers
Geometric isomers
Structure & Nomenclature Examples
Structure & Nomenclature Examples
Alkenes & Alkynes

Alkynes: C C triple bonds
– Named similarly with an –yne ending and give
position of triple bond
– More reactive than alkenes
Aromatic Hydrocarbons
Cyclic unsaturated hydrocarbons with
alternating single and double C=C bonds.
 Ring system often has common name.
 Less reactive than alkenes or alkynes

Bonding in Benzene
25.4 Organic Functional Groups
Site of reactivity
 R, R', R" represent the alkyl (hydrocarbon)
group(s) to which functional group is
attached.

Functional Group examples
Aspartame
Functional Group examples
H
H
NH2
O
N
HO
H
CH2
CH
CO2H
25.5 Chirality

Chiral compounds – compounds
containing carbon atoms with four
different attached groups
Br
– Examples: CHFClBr, CH3—C—CH2CH2CH3

H
Enantiomers – nonsuperimposable mirror
images
Enantiomers
Enantiomers
Chiral Compounds
D- sugars are preferred
 L- amino acids are preferred
 Drugs

– Ibuprofen: one effective, other inactive
– Naproxen: one effective, other toxic
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