Title: Guanidine
CAS Registry Number: 113-00-8
Additional Names: Aminomethanamidine; carbamamidine; carbamidine; aminoformamidine; iminourea
Molecular Formula: CH5N3
Molecular Weight: 59.07
Percent Composition: C 20.33%, H 8.53%, N 71.14%
Line Formula: (NH2)2C=NH
Literature References: Strong organic base existing primarily as guanidinium ion at physiological pH. Found in turnip juice, mushrooms, corn germ, rice hulls, mussels, earthworms. Prepn of nitrate from dicyanodiamide + ammonium nitrate: Smith et al., Ind. Eng. Chem. 23, 1124 (1931); Davis, Org. Synth. coll. vol. I (2nd ed., 1941) p 302; from SO2, CO2, + NH3: Boivin, US 2762843 (1956); from urea: Mackay, US 2590257 (1952 to Am. Cyanamid); Craig, Minor, US 3009949 (1961 to Deere); Shaver, US 3108999 (1963 to Monsanto); from ammonium thiocyanate or thiourea + ammonia: Watt, Makosky, Ind. Eng. Chem. 46, 2599 (1954). Pharmacology as muscle stimulant: A. I. Podlesnaya, Bull. Exp. Biol. Med. 61, 291 (1966). Clinical evaluation with pyridostigmine in Lambert-Eaton myasthenic syndrome: S. J. Oh et al., Muscle Nerve 20, 1146 (1997). Review of mode of action: D. R. Tershak et al., "Guanidine" in Handbook of Experimental Pharmacology Vol. 61, G. V. R. Born et al., Eds. entitled "Chemotherapy of Viral Infections" P. E. Came, L. A. Caliguiri, Eds. (Springer-Verlag, New York, 1982) pp 343-375. Review of structure activity studies: F. Davidoff, N. Engl. J. Med. 289, 141-146 (1973). General reviews: M. Schenck, Pharmazie 3, 5 (1948); G. Schaefer, "Guanidines and Biguanidines" in International Encyclopedia of Pharmacology and Therapeutics 107, M. Erecinska, Ed. (Pergamon, Oxford 1981) pp 165-185.
Properties: Deliquescent, cryst mass, mp ~50°. pKa ~12.5. Absorbs CO2 from air. Very sol in water, alcohol. On heating to 160° it is converted to melamine and NH3. Keep well closed. LD50 i.p. in mice: 350 mg/kg (Podlesnaya).
Melting point: mp ~50°
pKa: pKa ~12.5
Toxicity data: LD50 i.p. in mice: 350 mg/kg (Podlesnaya)
Derivative Type: Hydrochloride
CAS Registry Number: 50-01-1
Molecular Formula: CH5N3.HCl
Molecular Weight: 95.53
Percent Composition: C 12.57%, H 6.33%, N 43.99%, Cl 37.11%
Properties: Cryst powder. Freely sol in water, alcohol. Aq soln is neutral.
Derivative Type: Nitrate
CAS Registry Number: 506-93-4
Molecular Formula: CH5N3.HNO3
Molecular Weight: 122.08
Percent Composition: C 9.84%, H 4.95%, N 45.89%, O 39.32%
Properties: Cryst powder, mp 214°. Soluble in 10 parts water; in alcohol. Aq soln is neutral.
Melting point: mp 214°
Therap-Cat: Cholinergic.
Keywords: Cholinergic.
Guanidinium Aluminum Sulfate Hexahydrate Guano Guanochlor Guanosine Guanoxabenz

Skeletal formula of guanidine Skeletal formula of guanidine with the implicit carbon shown, and all explicit hydrogens added.
Ball and stick model of guanidine Spacefill model of guanidine
CAS number 113-00-8 YesY
PubChem 3520
ChemSpider 3400 YesY
EC number 204-021-8
DrugBank DB00536
MeSH Guanidine
ChEBI CHEBI:42820 YesY
Beilstein Reference 506044
Gmelin Reference 100679
Jmol-3D images Image 1
Image 2
Molecular formula CH5N3
Molar mass 59.07 g mol−1
Melting point 50 °C; 122 °F; 323 K
log P −1.251
Std enthalpy of
formation ΔfHo298
−57–−55 kJ mol−1
Std enthalpy of
combustion ΔcHo298
−1.0511–−1.0531 MJ mol−1
7–8 hours
LD50 475 mg kg−1 (oral, rat)
Related compounds
Related compounds
  • Urea
  • Biguanide
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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.