BASE-CATALYZED HYDROGEN-DEUTERIUM EXCHANGE IN BENZO DERIVATIVES OF FIVE-MEMBERED AROMATIC HETEROCYCLES. PART VII. PRIMARY HYDROGEN ISOTOPE EFFECTS IN SOME 5- AND 6-SUBSTITUTED BENZOTHIAZOLES

Abstract

The rates of the base-catalyzed hydrogen-deuterium exchange at position 2, and the reverse, in some 5-and 6-substituted benzothiazoles are reported. The plots of log k _sH, and log k _sD against the sgrave]_m + sgrave]_p values of the substituents, according to the Hammett-Jaffé equations, are slightly curved. The primary hydrogen isotope effect k _sH/k _sD varies between 0.7 and 2.3 and the plot of log k _sH/k _sD against the sgrave]_m + sgrave]_p values of the substituents is a more pronounced curve, showing a maximum near to the sgrave]_m + sgrave]_p value of ?0.3. By these investigations the simple utilization of the primary hydrogen isotope effect in the prediction of reaction mechanisms seems extremely hazardous.