Abstract
Rate constants are reported for the reaction of a series of 19 ring- substituted benzaldehydes with propylamine in methanol and in O-d-me- thanol at different temperatures and of three of them with 2-methoxy- ethylamine and 2,2-dimethoxyethylamine. The large direct solvent kinetic isotope effects (KSIE) (2.1-2.9), as well as the ΔH * (4.7-7.6 kcal mol -1 ) values vary smoothly with substituent. ΔS * (ca. -45 cal mol -1 K -1 ) is almost independent of substituent. These data indicate that there in no change in the rate-limiting step, and since the large KSIE and |ΔS * | can be related to significant solvation of the leading OH - group at the transition state, they agree with a mechanism invol- ving α-amino alcohol formation in a fast preequilibrium followed by rate-limiting OH - detachment yielding iminium ions
Published Version
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