Addition compounds of methyl substituted cyclic ethers with boron trifluoride

Abstract

A manometric method was used to study the addition compounds of boron trifluoride with 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2-methyltetrahydropyran and 2,6-dimethyltetrahydropyran. Physical characteristics are given. Methyl substitution in both tetrahydrofuran and tetrahydropyran causes the addition compound to be more highly dissociated, with the effect being much more pronounced for the latter. In spite of the increased dissociation, the addition compounds formed with the substituted five-membered ring ethers have higher enthalpies and entropies of dissociation than does that formed with the unsubstituted ether. In the six-membered ring system, however, all the thermodynamic values for the dissociation process are largest for the unsubstituted case.