What is "methanediol"

Methanediol, also known as formaldehyde monohydrate or methylene glycol, is an organic compound with chemical formula CH(OH). It is the simplest geminal diol, and formally the second simplest carbohydrate (after formaldehyde).

Methanediol is a product of the hydration of formaldehyde HC=O, and predominates in water solution: the equilibrium constant being about 10, and in a 5% by weight solution of formaldehyde in water, 80% is in the methanediol form.

The compound is of some relevance to astrochemistry.

Methanediol is listed as one of the main ingredients of " Brazilian blowout", a hair-straightening formula marketed in the US. The equilibrium with formaldehyde may cause some concern as formaldehyde in hair straighteners is a health hazard.