NH2CO2H

Carbamic acid, with the chemical formula NH2CO2H and commonly written as H2N–CO2H, is the simplest member of the carbamate family and the amino derivative of carbonic acid. It is a small, highly reactive molecule that is typically described as transient or unstable under ordinary conditions, tending to decompose.

In terms of structure, carbamic acid can be viewed as a carboxylic acid whose hydroxyl group is replaced by an amino group. It readily decomposes to ammonia and carbon dioxide: NH2CO2H → NH3 + CO2. Because of its instability, isolated, free carbamic acid is rarely observed; it mainly exists in equilibrium with related species in solution or in the presence of amines.

Formation and equilibria: Carbamic acid can be formed by the direct reaction of carbon dioxide with ammonia: CO2 + NH3 ⇌ NH2CO2H. In aqueous or amine-rich environments, it is short-lived and rapidly converts to ammonium carbamate or other carbamate derivatives: NH2CO2H + NH3 ⇌ NH4+NH2COO−. This chemistry explains its role as a transient intermediate in several industrial and biological processes.

Industrial and synthetic relevance: Carbamic acid is an intermediate in the industrial synthesis of urea, where CO2 reacts with ammonia to form ammonium carbamate, which then dehydrates to give urea. Derivatives of carbamic acid, known as carbamates, are important in organic synthesis and in CO2 capture technologies, where amines trap CO2 as carbamate or ammonium carbamate species.

Safety and occurrence: Carbamic acid itself is not typically isolated and is not a natural stable substance. Reactions involving it evolve gases such as CO2 and, in some systems, ammonia; appropriate ventilation and standard chemical-handling precautions are advised.