R. Pestman et al., THE FORMATION OF KETONES AND ALDEHYDES FROM CARBOXYLIC-ACIDS, STRUCTURE-ACTIVITY RELATIONSHIP FOR 2 COMPETITIVE REACTIONS, Journal of molecular catalysis. A, Chemical, 103(3), 1995, pp. 175-180
Four carboxylic acids with a number of alpha-hydrogen atoms ranging fr
om three to zero were tested in the selective hydrogenation to aldehyd
e. The acids used were acetic, propanoic, isobutyric, and pivalic acid
. The oxides of iron, vanadium, zirconium, and titanium were used as c
atalysts. It was found that by decreasing the number of alpha-hydrogen
atoms the selectivity to the aldehyde increased, while the formation
of the main by-product, ketone, was suppressed. It is suggested that t
his is due to the fact that the ketonisation proceeds via a ketene-lik
e intermediate, the formation of which needs the presence of alpha-hyd
rogen. Furthermore, the reactions to aldehyde and ketone seem to be in
competition with each other.