Guanidine

Guanidine is the compound with the formula HNC(NH₂)₂. It is a colourless solid that dissolves in polar solvents. It is a strong base that is used in the production of plastics and explosives. It is found in urine as a normal product of protein metabolism. Guanidine is the functional group on the side chain of arginine.

Structure

Guanidine can be thought of as a nitrogenous analogue of the carbonic acid functional group. That is, the C=O group in carbonic acid is replaced by a C=NH group, and each OH is replaced by a NH₂ group. A detailed crystallographic analysis of guanidine was elucidated 148 years after its first synthesis, despite the simplicity of the molecule. In the year 2013, the positions of the hydrogen atoms and their displacement parameters were accurately determined using single-crystal neutron diffraction.

Production

Guanidine can be obtained from natural sources, being first isolated by Adolph Strecker via the degradation of guanine.

The compound was first synthesized in 1861 by the oxidative degradation of an aromatic natural product, guanine, isolated from Peruvian guano. The commercial route involves a two step process starting with the reaction of dicyandiamide with ammonium salts. Via the intermediacy of biguanidine, this ammonolysis step affords salts of the guanidinium cation (see below). In the second step, the salt is treated with base, such as sodium methoxide.