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Guanidine: Wikis

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Guanidine
Skeletal formula of guanidine
Ball-and-stick model of guanidine
IUPAC name
Identifiers
CAS number 113-00-8 Yes check.svgY
SMILES
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
 Yes check.svgY (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].

Contents

Guanidinium cation

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

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-R 5. 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

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
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1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

GUANIDINE, CN 3 H 5 or HN: C(NH 2) 2j the amidine of amidocarbonic acid. It occurs in beet juice. It was first prepared in 1861 by A. Strecker, who oxidized guanine with hydrochloric acid and potassium chlorate. It may be obtained synthetically by the action of ammonium iodide on cyanamide, CN NH2+ NH 4 I=CN 3 H 5 HI

by heating ortho-carbonic esters with ammonia to 150 C.; but best by heating ammonium thiocyanate to 180 -190° C., when the thiourea first formed is converted into guanidine thiocyanate, 2CS(NH2)2=HN
C(NH2)2

[[Hcns+H2s]]. It is a colourless crystalline solid, readily soluble in water and alcohol; it deliquesces on exposure to air. It has strong basic properties, absorbs carbon dioxide readily, and forms welldefined crystalline salts. Baryta water hydrolyses it to urea. By direct union with glycocoll acid, it yields glycocyamine, NH2 (HN): C NH CH 2 CO 2 H, whilst with methyl glycocoll (sarcosine) it forms creatine, NH2 (NH): C N(CH3) CH2 C02H.

Many derivatives of guanidine were obtained by J. Thiele (Ann., 1892, 270, p. 1; 18 93, 2 73, p. 1 33; Ber., 1893, 26, pp. 2598, 2645). By the action of nitric acid on guanidine in the presence of sulphuric acid, nitroguanidine, HN: C(NH 2) NH NO 2 (a substance possessing acid properties) is obtained; from which, by reduction with zinc dust, amidoguanidine, HN :C(NH 2) NH NH 2, is formed. This amidoguanidine decomposes on hydrolysis with the formation of semicarbazide, NH 2 CO NH NH 21 which, in its turn, breaks down into carbon dioxide, ammonia and hydrazine. Amidoguanidine is a body of hydrazine type, for it reduces gold and silver salts and yields a benzylidine derivative. On oxidation with potassium permanganate, it gives azodicarbondiamidine nitrate, NH 2 (HN) C N: N C:(NH) NH 2 2HNO 3, which, when reduced by sulphuretted hydrogen, is converted into the corresponding hydrazodicarbondiamidine, NH 2 (HN):C NH NH C:(NH) NH 2. By the action of nitrous acid on a nitric acid solution of amidoguanidine, diazoguanidine nitrate, NH 2 (HN): C NH N 2 NO 3, is obtained. This diazo compound is decomposed by caustic alkalis with the formation of cyanamide and hydrazoic acid, CH4N3 N03=N3H+CN NH2+ HN03, whilst acetates and carbonates convert it into amidotetra zotic acid, H2N C?NH - N. Amidotetrazotic acid yields addition compounds with amines, and by the further action of nitrous acid yields a very explosive derivative, diazotetrazol, CN 3. By fusing guanidine with urea, dicyandiamidineH 2 N (HN): C NH CO NH 21 is formed.


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