Studies on lactone stabilities

Abstract

The theories of Bucourt concerning the stabilities of mono-and polycyclic compounds have been critically exarnined and modified. Ring strain (as measured by heats of combustion in the literature) may be calculated with irnproved accuracy by the modified theory. The theory has been further tested by a deterrnination of the stabilities (relative to the hydroxy-acids) in SO mole % aqueous tetrahydrofuran of the series of mono- and polycyclic 8 -lactones: y. y, 8 -trirnethyl- 8 - valerolactone, ~ and trans - 1-oxadecal-2-one, cis- and trans - 1-oxa-l0-methyldecal-Z-one, 6a-.!.-butyl-l-oxa-9a, 10 (3 -decal-Z-one, 6a -t-butyl-l-oxa-9(3, 10(3 -decal-Z-o~e, 4-oxa-5 U -estran-3-one, 4-oxa-SU-cholestan-3-one, and 4-oxa-S{3 -cholestan-3-one. Good agreement was found between experimental and ca1culated values, when account was taken of a hitherto unrecognized deformation of the cyc10hexane ring caused by bulky equatorial substituents. The effect of solvent composition on the equilibrium between y -hydroxybutyric acid and y -butyrolactone was studied using the solvents 0-80 mole % aqueous tetrahydrofuran, dioxane, acetone and dimethylsulfoxide. Minima and maxima of the ratio hydroxy-acid/lactone were observed as the water content decreased from 100%; the ratio at the minima and maxima decreased with rising temperature. Thermodynamic parameters have been calculated and explained in terms of an extension of current theories of the structure of aqueous organic solutions.