July 20, 2020
Explosives? COVID-19? I’m connected to both.
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Image of Guanidine 3D Image of Guanidine

Guanidine is a small, nitrogen-rich organic compound found in nature in plants (e.g., rice hulls and turnip juice) and animals (e.g., mussels and earthworms). Unlike its oxygen analogue, carbonic acid, it exists at ambient conditions (i.e., not in solution nor at cryogenic temperatures). Guanidine should not be confused with guanine, a purine derivative that is found in bat and bird feces.

Many literature sources state that guanine is very soluble in water; but, as shown in the fast facts table, it is only slightly soluble. It is, however, very hygroscopic. Its hydrochloride salt is highly water-soluble and is the usual article of commerce. The free base is extremely toxic, as shown in the hazard information table. 

Guanidine was discovered in nature in the late 19th century. In 1907, a German patent was awarded to Italian chemist Celso Ulpiani for the reaction of dicyanamide with strong acid to produce guanidine (actually, guanidinium) nitrate. Twenty-four years later, G.B.L. Smith, V. J. Sabetta, and O. F. Steinbach, Jr., at the Polytechnic Institute of Brooklyn (now New York University Tandon School of Engineering) published a comprehensive study of the conversion of dicyandiamide (aka 2-cyanoguanidine) to guanidinium nitrate and then to nitroguanidine, a powerful explosive.

Guanidine’s hydrothiocyanate salt has an interesting connection to the current COVID-19 pandemic. This past June, the US Food and Drug Administration warned laboratories not to use media that contain the thiocyanate salt or other guanidine-based chemicals to transport COVID-19 samples. The reason: Guanidine compounds can decompose to highly toxic hydrogen cyanide (HCN) gas. The FDA also advised that when personnel do not know the ingredients of a transport medium, they should handle it as though it contained a guanidine product. As of the date of FDA’s warning, no HCN-related injuries had been reported to the agency.

Guanidine hazard information

Hazard class*Hazard statement
Flammable liquids**, category 2H225—Highly flammable liquid and vaporChemical Safety Warning
Acute toxicity, oral, category 3H301—Toxic if swallowedChemical Safety Warning
Acute toxicity, dermal, category 3H311—Toxic in contact with skinChemical Safety Warning
Skin corrosion/irritation, category 1H314—Causes severe skin burns Chemical Safety Warning
Serious eye damage/eye irritation, category 1H318—Causes serious eye damageChemical Safety Warning
Acute toxicity, inhalation, category 3H331—Toxic if inhaledChemical Safety Warning
Specific target organ toxicity, single exposure, category 1H370—Causes damage to organsChemical Safety Warning

 *Globally Harmonized System of Classification and Labeling of Chemicals.
Explanation of pictograms.
**The low melting point of guanidine qualifies it as a hazardous liquid.

Guanidine fast facts

CAS Reg. No.113-00-8
Empirical formulaCH5N3
Molar mass59.07 g/mol
AppearanceHygroscopic white crystals
Melting point50 ºC
Water solubility1.84 g/L
Chemical Abstract Service - a division of ACS

Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

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