Question

What is a stepwise mechanism for the hydroxide ion base catalyzed tautomerization of acetone to the enol form?

Answer 1

`H_3C-C(=O)CH_3 + HO^(-) rightleftharpoons H_2C=C(O^-)(Na^+)CH_3`

Explanation:

Acetones can form equilibrium quantities of the enol:

`H_3C-C(=O)CH_3 rightleftharpoons H_2C=C(-OH)CH_3`

Of course, the equilibrium lies to the left as written, but given a strong base, the enolic hydrogen may be deporotonated to form the enolate:

`H_2C=C(-OH)CH_3 + ""^(-)OH rarr H_2C=C(-O^-)CH_3 + H_2O`

The enolate is itself in equilibrium with the carbanion:

`H_2C=C(-O^-)CH_3 rarr H_2^(-)C-C(=O)CH_3`

And the carbanion is used to make `C-C` bonds.