Computational experiment on hydroformylation and hydrogenation of ethyne catalyzed by Rh complex: a competitive study

A comprehensive theoretical investigation on the mechanism of hydroformylation and hydrogenation of ethyne by the rhodium catalyst at employing a nonlocal density functional method (B3LYP) and Møller-Plesset correlation energy correction at second-order, MP2 level independently. We have explored all critical elementary steps for the whole catalytic cycle, namely, the hydrogenation and hydroformylation of ethyne. There were a number of possible pathways for this catalytic cycle, originating from the ethyne association with catalyst. It came to the conclusion from computation that the acetenyl insertion into Rh-H bond was irreversible and the rate-limiting step for the whole catalytic cycle. It indicated that the energy barrier for hydrogenation of ethyne was obviously lower than that for hydroformylation so hydrogenation of ethyne could be easier than ethyne hydroformylation. The main product was olefin from hydrogenation that can be further hydroformylation to give birth to propanaldehyde at last. The other product was acrolein from hydroformylation.