title: Acid-catalyzed isomerization of pivalaldehyde to methyl isopropyl ketone via a reactive protosolvated carboxonium ion intermediate.
abstract: Quantitative rearrangement of pivalaldehyde to methyl isopropyl ketone is observed in acids such as trifluoromethanesulfonic acid, anhydrous HF, and trifluoroethyl alcohol-BF3 but not in trifluoroacetic acid. Studies in a mixture of trifluoroacetic acid and trifluoromethanesulfonic acid show that acids with H(o) < or = -11 are able to carry out complete isomerization. These results and density functional theory calculations at the B3LYP/6-31G level suggest that protonated pivalaldehyde undergoes further protosolvation at higher acidities to a reactive superelectrophilic species resulting in rearrangement. A mechanism for the pivalaldehyde rearrangement to methyl isopropyl ketone in strong protic acids involving a reactive protosolvated superelectrophilic intermediate is suggested. Aspects of the related mechanism of the reaction with isobutane with CO in HF/BF3 medium leading to methyl isopropyl ketone are also discussed.
authors.affiliation: Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Olah
authors.forename: T
authors.initials: T
authors.lastname: Mathew
authors.forename: E R
authors.initials: ER
authors.lastname: Marinez
authors.forename: P M
authors.initials: PM
authors.lastname: Esteves
authors.forename: M
authors.initials: M
authors.lastname: Etzkorn
authors.forename: G
authors.initials: G
authors.lastname: Rasul
authors.forename: G K
authors.initials: GK
authors.lastname: Prakash