CARBON-14 ISOTOPE EFFECTS IN THE ADDITION OF 2,4-DINITROBENZENESULFENYL CHLORIDE TO STYRENE-1-14C AND STYRENE-2-14C

The carbon-isotope effect reported here represents the first step in a general study of the mechanisms of simple electrophilic addition reactions by isotope effect techniques using the successive labeling approach. The addition of 2,4-dinitrobenzenesulfenyl chloride to styrene was chosen as a ''calibration case'' for the cyclic mechanism. The observed isotope effects at /sup ..cap alpha../C and /sup ..beta../C are fully consistent with the cyclic mechanism and probably inconsistent with the open carbenium ion mechanisms. The values of /sup 12/k//sup 14/k indicated in this report are averages (and standard deviations) of values for five different fractions of reaction ranging from 20% to 70% with the calculations being made by all four of the Tong and Yankwich equations for each fraction of reaction. Results indicated that there were no trends in the /sup 12/k//sup 14/k values as the fraction of reaction varied, and as can be seen by the low standard deviations, there was good agreement among the values calculated by the four equations. These two facts to indicate that the starting materials were of high chemical and radiochemical purity and that the procedures used in the isotope effect experiments were accurate and properly controlled.