Keto-enol Tautomerism - Erlenmeyer Rule

One of the early investigators into keto-enol tautomerism was Richard August Carl Emil Erlenmeyer. His Erlenmeyer rule (developed in 1880) states that all alcohols in which the hydroxyl group is attached directly to a double-bonded carbon atom become aldehydes or ketones. This occurs because the keto form is, in general, more stable than its enol tautomer. As the lower energy form, the keto form is favored at equilibrium.