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COMMUNICATIONS TO THE EDITOR
transfer agent in the vital transition state, probably in a general acid catalyzed detachment of the alkoxy “group” from the carbonyl-hydrate (>C(OH)*) of the lactone. For methyl phosphate hydrolysis (w = 6)’ an analogous mechanism, involving an intermediate with 5-coordinate phosphorus, is implied. As an empirical criterion of mechanism the above rules promise to succeed the Zucker-Hammett h y p o t h e s i ~ , ~which ,~ recently has been sharply criticized. Much of the difficulty stems from the fact that reactions with w values of about - 3 to $ 3 all give reasonably straight plots of log k+ against -Ho, with slope > 1.00 when w is negative and
