Vinyl alcohol

Tautomerization of acetaldehyde to vinyl alcohol

Under normal conditions, vinyl alcohol converts (tautomerizes) to acetaldehyde:

At room temperature, acetaldehyde (H₃CC(O)H) is more stable than vinyl alcohol (H₂C=CHOH) by 42.7 kJ/mol:

H₂C=CHOH → H₃CC(O)H                 ΔH_298,g = −42.7 kJ/mol

This keto-enol tautomerization has a high barrier and does therefore not occur near room temperature. This tautomerization can be catalyzed via photochemical process. These findings suggest that the keto-enol tautomerization is a viable route under atmospheric and stratospheric conditions, relevant to a role for vinyl alcohol in the production of organic acids in the atmosphere.

Relationship to polyvinylalcohol

Because of the instability of vinyl alcohol, the thermoplastic polyvinyl alcohol (PVA or PVOH) is made indirectly by polymerization of vinyl acetate followed by hydrolysis of the ester bonds (Ac = acetyl, HOAc = acetic acid):

n CH₂=CHOAc → (CH₂−CHOAc)_n(CH₂−CHOAc)_n + n H₂O → (CH₂−CHOH)_n + n HOAc

As a ligand

Several metal complexes are known that contain vinyl alcohol as a ligand. One example is Pt(acac)(η²-C₂H₃OH)Cl.

Occurrence in interstellar medium

Vinyl alcohol was discovered in the molecular cloud Sagittarius B using the 12-meter radio telescope at the Kitt Peak National Observatory. This vinyl alcohol being stable in the (dilute) interstellar medium shows that its tautomerization is not unimolecular.