<unk> s or urethanes are a group of organic compounds sharing a common functional group with the general structure -NH(CO)O-.<unk> s are esters of carbamic acid, NH2COOH, an unstable compound. Since carbamic acid contains a nitrogen attached to a carboxyl group it is also an amide. Therefore,<unk>  esters may have alkyl or aryl groups substituted on the nitrogen, or the amide function. For example, urethane or ethyl<unk> , is unsubstituted, while ethyl N–methylcarbamate has a methyl group attached to the nitrogen (see methyl isocyanate for formation of N-methylcarbamates).
Carbamate
Aniline
Ketone
Methyldopate
Propionic acid
Amphetamine
Alkane
Pyrovalerone