the chemistry of life: organic and biological chemistry blb 11 th chapter 25
TRANSCRIPT
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
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
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)
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-
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
25.4 Organic Functional Groups
Site of reactivity R, R', R" represent the alkyl
(hydrocarbon) group(s) to which functional group is attached.
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