|dc.description.abstract||This research was focussed on the effects of light, solvent and
substituents in the molybdenum-catalyzed oxidation of phenylmethyl sulfides
with t-Bu02H and on the effect of light in the molybdenum-catalyzed
epoxidation of l-octene with t-Bu02H.
It was shown that the Mo(CO)6-catalyzed oxidation of phenylmethyl
sulfide with t-Bu02H~ at 35°C, proceeds 278 times faster underUV light than
under laboratory lighting, whereas the Mo02(acac)2-catalyzed oxidation
proceeds only 1.7 times faster under UV light than under normal laboratory
lighting. The difference between the activities of both catalysts was
explained by the formation of the catalytically active species, Mo(VI).
The formation of the Mo(VI) species, from Mo(CO)6 was observed from
the IR spectrum of Mo(CO)6 in the carbonyl region.
The Mo(CO)6-catalyzed epoxidation of l-octene with t-Bu02H showed that
the reaction proceeded 4.6 times faster under UV light than in the dark or
under normal laboratory lighting; the rates of epoxidations were found to
be the same in the dark and under normal laboratory lighting.
The kinetics of the epoxidations of l-octene with t-Bu02H, catalyzed
by Mo02(acac)2 were found to be complicated; after fast initial rates, the
epoxidation rates decreased with time.
The effect of phenylmethyl sulfide on the Mo(CO)6-catalyzed epoxidation
of l-octene waS studied. It was shown that instead of phenylmethyl sulfide,
phenylmethyl sulfone, which formed rapidly at 85°C, lowered the reaction rate. The epoxidation of l-octene was found to be 2.5 times faster in
benzene than in ethanol.
The substituent effect on the Mo02(acac)2-catalyzed oxidations of p-OH,
p-CHgO, P-CH3' p-H, p-Cl, p-Br, p-CHgCO, p-HCO and P-N02 substituted
phenylmethyl sulfides were studied. The oxidations followed second order
kinetics for each case; first order dependency on catalyst concentration was
also observed in the oxidation of p-CHgOPhSMeand PhSMe.
It was found that electron-donating groups on the para position of
phenylmethyl sulfide increased the rate of reaction, while electronwithdrawing
groups caused the reaction rate to decrease. The reaction
constants 0 were determined by using 0, 0- and 0* constants. The rate
effects were paralleled by the activation energies for oxidation.
The decomposition of t-Bu02H in the presence of M.o (CO)6, Mo02 (acac)2
and VO(acac)2 was studied. The rates of decomposition were found to be very
small compared to the oxidation rates at high concentration of catalysis.
The relative rates of the Mo02(acac)2-catalyzed oxidation of
p-N02PhSMe by t-Bu02H in the presence of either p-CH30PhSMe or PhSMe clearly
show that PhSMe and p-CHgOPhSMe act as co-catalysts in the oxidation of
Benzene, mesity1ene and cyclohexane were used to determine the effect
of solvent in the Mo02 (acac)2 and Mo(CO)6-catalyzed oxidation of phenylmethyl
sulfide. The results showed that in the absence of hydroxylic solvent, a
second molecule of t-Bu02H was involved in the transition state. The
complexation of the solvent with the catalyst could not be explained.The oxidations of diphenyl sulfoxide catalyzed by VO(acac)2,
Mo(CO)6 and Mo02(acac)2 showed that VO(acac)2 catalyzed the oxidation
faster than Mo(CO)6 and Mo02 (acac)2_ Moreover, the Mo(CO)6-catalyzed
oxidation of diphenyl sulfoxide proceeded under UV light at 35°C.||en_US