Manganese(III) tetraphenylporphyrin acetate (Mn(III)(TPP)OAc) has been synthesized and characterised by C, H, N analysis, IR and electronic spectra. The electrochemical studies of the complex show a single quasireversible electron transfer process at E-p(c)=0.620 V. Polyisoprene and polychloroprene were epoxidized using Mn(TPP)OAc complex as catalyst and NaOCl or PhIO as oxygen donor. Both polyisoprene and polychloroprene were epoxidized completely within 7 h using NaOCl as oxygen donors and in 12 h using PhIO as the oxygen donor. The reaction was monitored by IR spectroscopy. The peak at 1020 cm(-1) due to -CH=CH- disappears completely and a peak has been observed at 970 cm(-1), characteristic of oxiranes, indicating the complete conversion of the polyene to polyepoxide. Cyclohexene and styrene were epoxidised using Mn(TPP)OAc complex as catalyst and NaOCl and PhIO as oxygen donors. Epoxidation of styrene is complete in 30 min with 100% yield of styrene epoxide using PhIO, whereas it takes 1 h for the completion of the reaction using NaOCl and gives mixed products with 59.71% styrene epoxide, 21.89% benzaldehyde and 18.40% phenylacetaldehyde. Epoxidation of cyclohexene is complete in 1 h using NaOCl with 33.57% cyclohexeneoxide, 13.01% of cyclohex-2-ene-1-ol and 53.42% of cyclohex-2-ene-1-one, whereas the reaction was only 31.22% completed in 1 h using PhIO with 22.06% yield of 2-cyclohexeneoxide, 4.23% of cyclohex-2-ene-1-ol and 4.93% of cyclohex-2-ene-1-one. The reaction was monitored by using gas chromatography.