Guanidine

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Guanidine
Skeletal formula of guanidineSkeletal formula of guanidine with the implicit carbon shown, and all explicit hydrogens added.
Ball and stick model of guanidineSpacefill model of guanidine
Identifiers
CAS number113-00-8 YesY
PubChem3520
ChemSpider3400 YesY
UNIIJU58VJ6Y3B YesY
EC number204-021-8
DrugBankDB00536
MeSHGuanidine
ChEBICHEBI:42820 YesY
ChEMBLCHEMBL821 YesY
Beilstein Reference506044
Gmelin Reference100679
Jmol-3D imagesImage 1
Image 2
Properties
Molecular formulaCH5N3
Molar mass59.07 g mol−1
Melting point50 °C (122 °F; 323 K)
log P−1.251
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−57–−55 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−1.0511–−1.0531 MJ mol−1
Pharmacology
Elimination
half-life
7–8 hours
Hazards
LD50475 mg/kg (oral, rat)[2]
Related compounds
Related compounds
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references
 
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Not to be confused with Guanine, Guanosine, or Guanfacine.
Guanidine
Skeletal formula of guanidineSkeletal formula of guanidine with the implicit carbon shown, and all explicit hydrogens added.
Ball and stick model of guanidineSpacefill model of guanidine
Identifiers
CAS number113-00-8 YesY
PubChem3520
ChemSpider3400 YesY
UNIIJU58VJ6Y3B YesY
EC number204-021-8
DrugBankDB00536
MeSHGuanidine
ChEBICHEBI:42820 YesY
ChEMBLCHEMBL821 YesY
Beilstein Reference506044
Gmelin Reference100679
Jmol-3D imagesImage 1
Image 2
Properties
Molecular formulaCH5N3
Molar mass59.07 g mol−1
Melting point50 °C (122 °F; 323 K)
log P−1.251
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−57–−55 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−1.0511–−1.0531 MJ mol−1
Pharmacology
Elimination
half-life
7–8 hours
Hazards
LD50475 mg/kg (oral, rat)[2]
Related compounds
Related compounds
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

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[edit]

Guanidine can be thought of as a nitrogenous analogue of 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.[3] A detailed crystallographic analysis of guanidine was elucidated 148 years after its first synthesis, despite the simplicity of the molecule.[4] In the year 2013, the positions of the hydrogen atoms and their displacement parameters were accurately determined using single-crystal neutron diffraction.[5]

Production[edit]

Guanidine can be obtained from natural sources, being formed by the oxidation of guanine.

The molecule was first synthesized in 1861 by the oxidative degradation of an aromatic natural product, guanine, isolated from Peruvian guano.[6] 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. In the second step, the salt is treated with base, such as sodium methoxide.[7]

Guanidinium cation[edit]

Guanidine is protonated in physiological conditions. This conjugate acid is called the guanidinium cation, [CH6N3]+. The guanidinium cation has a charge of +1. It is a highly stable cation in aqueous solution due to the efficient resonance stabilization of the charge and efficient solvation by water molecules. As a result, its pKa is 13.6[8] meaning that guanidine is a very strong base in water.

Notable guanidinium salts include guanidinium chloride (GndCl), which has chaotropic properties and is used to denature proteins. Guanidine hydrochloride is known to denature proteins with a linear relationship between concentration and free energy of unfolding. Another such salt is guanidinium thiocyanate; creatine is a derivative of the guanidinium cation.

Guanidine derivatives[edit]

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, and the group is related structurally to amidines and ureas. Examples of guanidines are arginine, triazabicyclodecene, and saxitoxin. Another derivative is guanidinium hydroxide, the active ingredient in some non-lye hair relaxers. Guanidinium salts are well known for their denaturing action on proteins; guanidinium chloride is one of the most effective denaturants. In 6 M aqueous GndHCl, almost all proteins lose their ordered "secondary structure" (that results from intramolecular noncovalent interactions) and become "randomly coiled"; that is, their secondary structure interactions are disrupted by the dissolved guanidinium, leaving only the primary covalent structure of their polyamide backbones. Guanidine hydrochloride[9] is used as an adjuvant in treatment of botulism, introduced in 1968,[10] but now its role is considered controversial[11] - because in some patients there was no improvement after this drug administration.

See also[edit]

References[edit]

  1. ^ "Guanidine - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification. Retrieved 29 February 2012. 
  2. ^ http://chem.sis.nlm.nih.gov/chemidplus/rn/50-01-1
  3. ^ M. Goebel, T.M. Klapoetke (2007). "First structural characterization of guanidine". Chem. Commun. 43 (30): 3180–2. doi:10.1039/B705100J. 
  4. ^ T. Yamada, X. Liu, U. Englert, H. Yamane, R. Dronskowski (2009). "Solid-state structure of free base guanidine achieved at last". Chem. Eur. J. 15 (23): 5651–5. doi:10.1002/chem.200900508. PMID 19388036. 
  5. ^ P. K. Sawinski, M. Meven, U. Englert, R. Dronskowski (2013). "Single-Crystal Neutron Diffraction Study on Guanidine, CN3H5". Cryst. Growth Des. 13: 1730–5. doi:10.1021/cg400054k. 
  6. ^ A. Strecker (1861). Liebigs Ann. Chem. 118: 151. 
  7. ^ Thomas Güthner, Bernd Mertschenk and Bernd Schulz "Guanidine and Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a12_545.pub2
  8. ^ Perrin, D.D., Dissociation Constants of Organic Bases in Aqueous Solution, Butterworths, London, 1965; Supplement, 1972.
  9. ^ http://www.ncbi.nlm.nih.gov/pubmed/389150
  10. ^ http://jama.ama-assn.org/content/240/21/2276.abstract
  11. ^ Pediatric anaerobic infections: diagnosis and management, p.529