THE MECHANISMS OF OXYMERCURATION

Abstract

The oxymercuration of norbornenes has been found to be acid-catalyzed, and to give oxymercurials which have a higher dipole moment and greater stability toward deoxymercuration than do their diastereomers in which the configuration of the mercuri linkage has been inverted. Since these properties can be correlated with those of the oxymercurials from norbornenedicarboxylic acids (partly published heretofore and elaborated in the present report) the configurations of which are known, it follows that the configurations of the oxymercurials from norbornene are ↑↓ (trans). But these configurations must be opposite to those of the oxymercurials from cyclohexene, cyclopentene, α-terpineol, and the geoisomeric stilbenes, the formations of which are not acid-catalyzed and the dipole moments of which are lower than those of the diastereomers inverted with respect to the mercuri linkage. The configuration of these oxymercurials must be ↓↓ (cis) and the mechanism of their formation must be different from the acid-catalyzed oxymercuration of norbornene. The mechanism for cis (↓↓) addition has previously been suggested as non-ionic. Calculation of the electric moments of these ↓↓ diastereomers shows that hindrance to group rotation must prevail. It is reasonable to attribute the relative ease with which they may be deoxymercurated to this hindrance.