Concerning in 2-methylphenol and its derivatives. A proximate coupling

Abstract

In 2-chloro-6-methylphenol in CCl4 solution, [Formula: see text] the spin–spin coupling between the hydroxyl and methyl protons, is + 68(3) mHz. In this compound, the hydroxyl group lies trans to the methyl group. If the coupling becomes −120 ± 60 mHz in a cis orientation of these two groups, then the apparent vanishing of [Formula: see text] in some derivatives of 2-methylphenol is understandable, as well as its presence in other derivatives. Computations of this coupling imply its proximate mechanism and can rationalize its value of −220 ± 20 mHz in 2-tert-butyl-6-methylphenol. Analogies are noted with [Formula: see text] in 2-trifluoromethyl phenol and with a coupling in styrene, which also appears to vanish in certain orientations of the vinyl group.