The role of carboxylic acids on a Na2WO4/H2WO4-based biphasic homogeneous alkene epoxidation, using H2O2 as oxidant

The role of various carboxylic acids (substituted/unsubstituted acetic, benzoic and salicylic acids) with various electron donating and/or withdrawing substituents on the Na2WO4/H2WO4-catalysed, biphasic epoxidations of cyclooctene and 1-octene, using H2O2 as terminal oxidant has been investigated. The presence of the different acids in catalytic amounts widely affects the catalytic activity of the above system depending on the nature of their substituents. The results obtained have been discussed in the light of the stereo/electronic effects of these substituents. It has been observed that the added substituted/unsubstituted acetic and benzoic acids generally enhance the rate of the epoxidation while salicylic acids significantly decrease the catalyst activity, under the same conditions, most likely due to the additional deactivating hydroxy moiety.

Screening of various carboxylic acids as acid additives with different substitutents with the catalyst system below towards alkene epoxidation, leads to the observation that the substituted/unsubstituted acetic and benzoic acids generally enhance the rate of the epoxidation while salicylic acids significantly decrease the catalyst activity and chloroacetic acid as the best additive to enhance the rate of epoxidation. Figure optionsDownload as PowerPoint slide