Structural and spectroscopic characterisation of C4 oxygenates relevant to structure/activity relationships of the hydrogenation of α,β-unsaturated carbonyls

Abstract

Supported palladium catalysts are widely used in selective hydrogenation reactions, thus it is desirable to correlate product yields with catalyst performance, so as to optimize catalyst productivity. One method to achieve this goal is to use gas phase infrared spectroscopy to follow the evolution of the gas phase composition as a catalytic reaction progresses and hence determine the kinetics of the reaction. The method is critically dependent on reliable identification and assignment of the modes of each of the species that may be present. We plan to use the same method to investigate how the morphology of Pd crystallites can influence selectivity branching in gas phase hydrogenation reactions of α,β-unsaturated carbonyl compounds, specifically by following the hydrogenation of 3-butyne-2-one to 3-butene-2-one to 2-butanone and finally to 2-butanol. In the present work, we have investigated the conformational isomerism and calculated the vibrational spectra of the C4 oxygenates using density functional theory. The calculations are validated by comparison to the inelastic neutron scattering and infrared spectra of the compounds. KeywordsInelastic neutron scattering spectroscopy; Infrared spectroscopy; Density functional theory; Conformational isomerism Highlights• The conformational isomerism in 3-butyne-2-one, 3-butene-2-one, 2-butanone and 2-butanol oxygenates has been investigated.• Complete vibrational assignments for 3-butyne-2-one, 3-butene-2-one, 2-butanone and 2-butanol are obtained from density functional theory.• The assignments have been tested by comparison to inelastic neutron scattering spectra. Graphical abstract3