Isomerization of linoleic acid hydroperoxides under argon and under degassed conditions.

Abstract

The rearrangement of linoleic acid hydroperoxides, (9Z, 11E)-13-hydroperoxy-9, 11-and (9E, 11E)-13-hydroperoxy-9, 11-octadecadienoic acids (13-Z, E-LOOH and 13-E, E-LOOH, respectively), occurred under argon and under degassed conditions, as well as under aerobic conditions. In argon-saturated benzene, 13-Z, E-LOOH isomerized to 9-E, E-and 13-E, E-LOOHs, and 13-E, E-LOOH to 9-E, E-LOOH ; the E, E-isomers hardly isomerized to E, Z-isomers. The hydroperoxides isomerized rapidly in benzene and chloroform, but slowly in n-propyl ether and methanol. However, they decomposed extensively in chloroform, and moderately in benzene and methanol. Decomposition was very slight in n-propyl ether. The isomerization rate of the 9Z, 11E-isomer was much higher than that of the 9E, 11E-isomer. Since the rate was found to be slow under degassed conditions, traces of dissolved molecular oxygen may be responsible for the isomerization.