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 (CnHn)

Structural isomers – same number and type of atoms but different bonding arrangements

3-D ArrangementTetrahedral 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. Identify longest C chain → base name

2. Number C atoms – lowest number nearest substituent (branch)

3. Give position and name substituents.

4. 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 strained & unstablestructure structure

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-

Geometric isomers

Structural 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

N

H H

HHO

O CH2 CH CO2H

NH2

25.5 Chirality Chiral compounds – compounds

containing carbon atoms with four different attached groups

– Examples: CHFClBr, CH3—C—CH2CH2CH3

Enantiomers – nonsuperimposable mirror images

Br

H

Enantiomers

Enantiomers

Chiral Compounds D- sugars are preferred L- amino acids are preferred Drugs

– Ibuprofen: one effective, other inactive

– Naproxen: one effective, other toxic