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Gamma irradiation of alpha -pinene at 30 deg results in formation of hydrogen, isomers of alpha -pinene, and polymeric material corresponding to a number-average molecular weight given by (C/sub 10/H?sub 16/)/sub 3.1 plus or minus 0.1/. Initial G yields of hydrogen and monomer conversion into polymer are 0.5 and 5.2 molecules per 100 ev, respectively. Isolation of the individual isomerization products by gas-liquid chromatography and their identification by infrared and ultraviolet spectroscopy reveal dipentene and ocimene as the major constituents with initial G values of 0.9 and 2.6, respectively. Spectrophotometric determination of ocimene by the absorption peak at 237 m mu gives a G value of 2.8. (+)- alpha Pinene is partly racemized on irradiation, with a G yield of 1.6. Formation of ocimene is attributed to release of excess vibrational energy in an alpha -pinene molecule subjected to excitation. The racemization implies formation of an intermediate which can revert to either the (+)- or the (--)-form. It is suggested that an internal ion pair intermediate could result from the primary processes of ionization and electron capture within a rearranged alpha -pinene molecule; the subsequent diverse reactions of the proposed internal ion pair are depicted as leading to dipentene, polymer,more » or optically inactive alpha -pinene. (auth)« less |
