在有机化学中，烷基取代物是缺少一个氢的烷烃。烷基一词故意不具体，包括许多可能的取代。无环烷基具有通式CNH2N+ 1。环烷基是由环烷烃通过从环上除去氢原子而得到的，具有通式CnH2n-1。通常烷基是大分子的一部分。在结构式中，符号R用于指定一个通用的（未指定的）烷基。最小的烷基是甲基，其分子式为CH3。
(1R)-1-(Thiophen-2-yl)ethan-1-amine
1-(6-Cyclopropylpyridin-3-yl)ethanamine
4,4-Dimethylcyclopentane-1,3-dione
Bis(2-ethylhexyl) cyclohexane-1,2-dicarboxylate
4-Octadecylmorpholine
4-Methylpentane-1,4-diol
Methyl dec-9-enoate
5-Methyl-3,4-dihydroquinolin-2(1H)-one
1-(2-Methoxyethyl)-3,5-dimethyl-4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole
2-(4-Ethylcyclohexyl)acetic acid
2-Ethylhexyl 3,5,5-trimethylhexanoate
2-Ethylhexyl 4-(methylamino)benzoate
4-(tert-Butoxy)-2-methylbutan-2-ol
2-Bromo-5-(2-octyldodecyl)thiophene
Stannane, 1,1'-dithieno[3,2-b:2',3'-d]thiophene-2,6-diylbis[1,1,1-tributyl-
4,8-Bis(5-hexylthiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene
(4,8-Bis(5-octylthiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane)
2-Bromo-4,8-bis((2-octyldodecyl)oxy)benzo[1,2-b:4,5-b']dithiophene
4,9-Dibromo-2,7-bis(2-hexyloctyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone
4-(2-Octyldodecyl)thiophene-2-carbonitrile
2-(Triisopropylsilyl)-5-(trimethylstannyl)thiazole
(4,8-Bis(5-(2-ethylhexyl)-4-octylthiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane)
5-(p-Tolyl)-1,3,4-thiadiazole-2(3H)-thione
2-Bromo-5-propylpyridine
N,N-Dimethylstearamide
3,7-Dibromo-10-(4-octylphenyl)-10H-phenothiazine
Bis(2-ethylhexyl) terephthalate
3-(tert-Butyl)-1-(p-tolyl)-1H-thieno[2,3-c]pyrazole-5-carboxylic acid
3-(4-Isopropyl-4H-1,2,4-triazol-3-yl)aniline
