ACID-CATALYZED DEHYDRATION AND ACETOLYSIS OF TERTIARY METHYL-CARBINOLS AND TERT-BUTYLCARBINOLS - EMPIRICAL FORCE-FIELD TREATMENT OF TERT-BUTYL-METHYL REACTIVITY RATIOS IN SOLVOLYSIS REACTIONS OF ALCOHOLS AND PARA-NITROBENZOATES

Hate constants have been determined for the sulfuric acid catalyzed solvolysis in anhydrous acetic acid of 28 tertiary carbinols. 23 of which contain either a methyl or a tert-butyl substituent at the tertiary position. The kinetic effect of replacing Me by f-Bu ranges from 0.03 for alkyl(l-adamantyl)-fm-butylcarbinols to 103-3 for 2-alkyl-2-adamantanols. For five systems the l-Bu/Me values are smaller than those found in the solvolysis of the corresponding p-nitrobenzoates by factors ranging from 101 9 to 104-6, depending on the structure. Strain energy calculations by the empirical force field method (molecular mechanics) provide a coherent, interpretation of reactivity data for both alcohols and p-nitrobenzoates, provided that the hydrocarbon model employed for the ground state takes into account the greater steric requirements of the OPNB leaving group : OPNB is modeled by Me; OH by H. In this way self-consistent reactivity/Δ (strain) correlations are obtained for both the f-Bu/Me ratios and substituent effects in the 2-alkyl-2-adamantyl system. Nevertheless, the fact that the individual reactivities of disparate systems are poorly correlated by strain energy calculations limits their utility as a probe for detecting anomalous behavior in the solvolysis of exo-and endo-2-norbornyl derivatives, for example. Data for the 7-norbornyl system suggest that the carbonium ion force field, used as a model of the transition state, overestimates the importance of angle strain. © 1979, American Chemical Society. All rights reserved.