Migration of hydroxyl in secondary systems during solvolysis in acid solution

Abstract

Can. J. Chem. 55,3774 (1977). A system of compounds has been prepared which is well adapted for displaying the role of trans vicinal, secondary hydroxyl in solvolysis. On methanolysis in acid solution, compounds 5, 7a, and 8a all gave the same products, 9a and 10a, and in practically the same proportions, suggesting that at least one intermediate was common to all three reactions. These intermediates were such that 7a and 8u were not interconverted during the solvolysis, a fact in support of 6 as a common intermediate. Several alternative explanations were shown to be untenable, largely by taking advantage of the remarkable differences between hydroxyl and methoxyl. The work provides the most decisive evidence available for the covalent participation of hydroxyl as a neighbor group in the solvolysis of secondary systems, and contributes also to the study of the reverse reaction, the acid-catalyzed scission of epoxides. On prepare un systeme de composes lequel est bien adapte pour mettre en evidence le r61e du groupe hydroxyle trans vicinal dans des reactions de solvolyse. La mkthanolyse en solution acide des composks 5, 7a et 8a conduit aux mCmes produits 9a et 10a et essentiellement aux m&mes proportions suggerant qu'au moins un intermediaire est commun aux trois reactions. Ces intermediaires sont de telle sorte que 7a et 8a ne sont pas convertis I'un dans I'autre pendant la solvolyse, ce qui est en accord avec l'hypothese que 6 soit un intermediaire commun. Plusieurs interprktations ne peuvent Ctre soutenues, essentiellement parce qu'elles ne tiennent pas compte des grandes differences entre un groupe hydroxyle et methoxyle. Ce travail apporte l'evidence tres nette de la participation covalente du groupe hydroxyle comme groupe voisin dans la solvolyse de systemes secondaires et contribut aussi a l'etude de la reaction inverse, la scission catalyske par un acide des Cpoxydes.[Traduit par le journal]

Kinetics and Mechanisms of Hydrothermal Dehydration of Cyclic 1,2- and 1,4-Diols

“…In a previous study of deoxygenation of trans-1,2-cyclohexanediol using an organometallic catalyst, it was suggested that dehydration might proceed via an epoxide intermediate. 38,51,52 No epoxide is detected in the products of the current reaction, but this does not rule out an epoxide intermediate because it could undergo rapid hydrolysis. 53 To test for the intermediacy of an epoxide, hydrothermal reaction was performed starting with 1,2-epoxycyclohexane under the same conditions as the diol reactions.…”

The competitive scissions of cycloalkane oxiranes by charged and neutral nucleophiles in acidic aqueous methanol

“…The preparation of compounds used in this work, when not reported here, can be found in earlier papers (7,8,10 and references cited therein). Epoxides 14 and 15 and 17 and 18 were each free of their respective isomers and had a purity of better than 99.9%.…”