HOMOMOLECULAR ESTERIFICATION OF ALDEHYDES CATALYZED BY HYDRIDOTETRAKIS(TRIPHENYLPHOSPHINE)RHODIUM(I)

Article abstract of DOI:10.1016/0022-328X(83)87185-X

Homomolecular esterification of benzaldehyde has been carried out under mild conditions using RhH(PPh3)4 as catalyst.A kinetic study of the reaction has revealed a law rate of the form r=k².The rate-limiting step in the mechanism is the complexation of the second aldehyde molecule with the catalyst.As expected from this result, the lactonisation of ortho-phthalaldehyde is instantaneous at 19 deg C.In this homomolecular esterification RhH(PPh3)3 is the catalytic species and slowly transfers its hydrogen ligand to benzaldehyde to form benzyl alcohol in concentration less than half of that of the catalyst.The complex Rh(PPh3)3 which is formed also catalyses the homomolecular esterification, but 1.6 times less readily than RhH(PPH3s)3.