Formation of Benzene and Toluene from Acetylene-14c in the Avocado.

In previous communications from this laboratory on the fate of ethylene in avocados, it was shown that approximately 127, of the radioactivity of metabolized ethylene-3H appeared in the methyl group of toluene (1) whereas only approximately 0.2% of the radioactivity of metabolized ethylene-14C appeared in toluene (2). On the other hand, benzene produced by the metabolism of ethylene-3H and ethylene-14C contained similar amounts of the total incorporated, 1% and 4%, respectively (2). These results suggest that, in the metabolism of ethylene, a considerable port,ion of the hydrogen is removed by some dehydrogenation process, and this hydrogen proceeds along a pathway different from that followed by the carbon, as is illustrated by the labeling of toluene. Nevertheless, part of the hydrogen and carbon of ethylene is metabolized along the same pathway, as illustrated by the labeling of benzene. This postulate suggests that acetylene may be metabolized more directly to some of the same metabolit.es as ethylene. Further, acetylene is known to produce some of t.he same physiological effects as ethylene, e.g. acetylene induces flowering in pineapple plants (3) and epinasty in plants (4). The concentration of acetylene required for the latter effect is 500 times greater than that with ethylene (4). The present report is concerned with the metabolism of acetylene-% by avocado fruit. Under the same conditions used with labeled ethylene (1, 2), approximately 9 times as much acetylene-r4C as ethylene was metabolized in a 4-hour period. Two-fifths of the metabolized acetylene was found in the respiratory COZ. Approximately three-fourths of the remainder in the fruit was volatile. The benzene and toluene were concentrated and derivatives were made therefrom as in the ethylener4C experiments (2). The benzene isolated from fruit treated with acetylene contained approximately 25 times as much 14C as the benzene from ethylene-treated fruit, whereas the 14C in toluene was the same for the two treatments.