戊烷分子式C5H12,其同分異構體有三種：

1.CH3-CH2-CH2-CH2-CH3 正戊烷

2.CH3-CH(CH3)-CH2-CH3 異戊烷（2-甲基丁烷）

3.C(CH3)4 新戊烷（22-二甲基丙烷）

己烷：

CH3-(CH2)4-CH3

CH3CH(CH3)-(CH2)3-CH3

CH3CH2CH(CH3)-(CH2)2-CH3

CH3CH(CH3)CH(CH3)CH2CH2CH3

CH3CH(CH3)CH2CH(CH3)CH2CH3

CH3CH(CH3)CH2CH2CH(CH3)CH3

CH3CH(CH3)CH(CH3)CH(CH3)CH3

庚烷：

CH3-(CH2)5-CH3

(CH3)2-CH-(CH2)3-CH3

CH3CH2CH(CH3)CH2CH2CH3

(CH3CH2)3CH

(CH3)3-C-CH2CH2CH3

(CH3CH2)2-C-(CH3)2

(CH3)2-CH-CH(CH3)-CH2CH3

(CH3)2-CH-CH2-CH-(CH3)2

(CH3)3-C-CH-(CH3)2