Methyl
R-CH3
Ethyl
R-CH2CH3
Phenyl
R-C6H5
Carbonyl (aldehyde)
R-CHO
Carbonyl (ketone)
R-CO-R
Carboxyl
R-COO
Hydroxyl (alcohol)
R-OH
Enol
R-C(OH)=CH2
Ether
R-O-R
Ester
RCOOR
Acetyl
R-O-(C=O)-CH3
Anhydride (two carboxylic acids)
R-(C=O)-O-(C=O)-R
Amino (protonated)
R-NH3+
Amido
R-C=O-NH2
Imine
R2C=NR
N-substituted imine (Schiff base)
R-C(=N-R)-R
Guanidinium
R-NH-C(=NH2+)NH2
Imidazole
R-(C=CH-N=CH-NH-) 5 member ring
Sulfydryl
R-SH
Disulfide
R-S-S-R
Thioester
R-C(=O)-S-R
Phosphoryl
R-O-PO2-OH
Phosphoanhydride
R-O-P(O)O(-)-O-P(O)O(-)-O-R
mixed anhydride
Carboxylic acid and phosphoric acid; also called acyl phosphateR-C=O-O-P=O-O(-)-OH