guanidine

Guanidine
IUPAC name	Guanidine
Identifiers
CAS number	113-00-8 Y
SMILES	C(=N)(N)N
Properties
Molecular formula	CH5N3
Molar mass	59.07 g/mol
Melting point	50 °C
Basicity (pKb)	1.5
Hazards
EU Index	Not listed
Related compounds
Related compounds	Guanidinium chloride Nitroguanidine
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Guanidine is a crystalline compound of strong alkalinity formed by the oxidation of guanine. It is used in the manufacture of plastics and explosives. It is found in urine as a normal product of protein metabolism. The molecule was first synthesized in 1861 by the oxidative degradation of an aromatic natural product, guanine, isolated from Peruvian guano^[1]. Despite the provocative simplicity of the molecule, the crystal structure was first described 148 years later^[2].

Guanidinium cation

Guanidine is protonated in physiological conditions, giving it a charge of +1 and a pK_a of 12.5. This conjugate acid of guanidine is called the guanidinium cation, [CH₆N₃]⁺.

ball-and-stick model

resonance hybrid

canonical forms

Notable guanidinium salts include guanidine hydrochloride, which has chaotropic properties and is used to denature proteins. Empirically, guanidine hydrochloride is known to denature proteins with a linear relationship between concentration and free energy of unfolding. Another such salt is guanidinium thiocyanate.

Guanidine derivatives

The general structure of a guanidine

Guanidines are a group of organic compounds sharing a common functional group with the general structure (R¹R²N)(R³R⁴N)C=N-R⁵. The central bond within this group is that of an imine; the other recognizable motif within this group is an aminal. Examples of guanidines are arginine, triazabicyclodecene and saxitoxin. other derivatives could include guanidine hydroxide, the active ingredient in some non-lye relaxers. Guanidinium salts are well known for their denaturing action on proteins. Guanidinium chloride is one of the most effective denaturants. In 6 M GndHCl all proteins with an ordered structure lose their structure, and most of them become randomly coiled, that is, they do not contain any residual structure.

Use as an alternative fuel

Guanidine is currently being considered as an alternative fuel. ^[3] In the presence of a catalyst, a mole of free-base guanidine combines with 2 moles of water to form 3 moles of ammonia and 1 mole of carbon dioxide. The ammonia can be used directly as a fuel for internal combustion engines, or decomposed into nitrogen and hydrogen gas for use in fuel cells. The guanidine could be supplied as a fuel in solid form as pure guanidine (melting point ~ 50 C) or as a lower melting point eutectic mixture with urea.^[3] Guanidine could also be supplied as solutions in ethanol, as a replacement for the gasoline component in E85 fuel.

See also

• Guanidinium thiocyanate
• Guanidine nitrate

References

1. ^ A. Strecker, Liebigs Ann. Chem. 1861, 118, 151.
2. ^ T. Yamada, X. Liu, U. Englert, H. Yamane, R. Dronskowski, Chem. Eur. J. 2009, 15, 5651.
3. ^ ^{a b} European Patent Office application EP20050746871