AN ELIMINATION REACTION WITH KINETICS CHARACTERISTIC OF ELCB MECHANISM

The dehydrochlorination of erythro-4,4′-dichlorochalcone dichloride, in absolute ethanol at 25°, is subject to general base catalysis. The rate is a nonlinear function of the buffer concentration. The reaction is inhibited by acid. The trans-elimination product is predominantly formed from the erythro as well as from the more reactive threo substrate. A two-step mechanism, involving ionization followed by uncatalyzed cleavage of the carbanion, is consistent with the kinetics. Unless the carbanion is extremely short lived, however, some other explanation of the observed acid inhibition is required, since extensive deuterium exchange in the substrate does not take place. © 1968, American Chemical Society. All rights reserved.