EPOXIDATION OF ISOBUTYLENE 251

(Isobutylene Oxide Production)

Isobutylene oxide is produced in a way similar to propylene oxide and butylene oxide by a chlorohydrination route followed by reaction with Ca(OH)₂. Direct catalytic liquid-phase oxidation using stoichiometric amounts of thallium acetate catalyst in aqueous acetic acid solution has been reported. An isobutylene oxide yield of 82% could be obtained. Direct non-catalytic liquid-phase oxidation of isobutylene to isobutylene oxide gave low yield (28.7%) plus a variety of oxidation products such as acetone, ter-butyl alcohol, and isobutylene glycol:

Hydrolysis of isobutylene oxide in the presence of an acid produces isobutylene glycol:

Isobutylene glycol may also be produced by a direct catalyzed liquid phase oxidation of isobutylene with oxygen in presence of water. The catalyst is similar to the Wacker-catalyst system used for the oxidation of ethylene to acetaldehyde. Instead of PdCl₂/CuCl₂ used with ethylene, a TlCl₃/CuCl₂ catalyst is employed:

Liquid-phase oxidation of isobutylene glycol produces othydroxyisobutyric acid. The reaction conditions are 70–80°C at pH 2–7 in presence of a catalyst (5% pt/C):

Dehydration of the acid produces 95% yield of methacrylic acid: