, and VICTOR MARK. Can. J. Chem. 56.1261Chem. 56. (1978.A high resolution proton magnetic resonance investigation of the hindered rotation of the dichloromethyl groups as a function of temperature in a,a,a1,a',3,4,6-heptachloro-o-xylene (HCOX) has been conducted using dynamic nuclear magnetic resonance line shape analysis, supplemented with a homonuclear double resonance saturation transfer technique. The rate process in HCOX involves a coupled rotation of the two substituted methyl groups and the nonmutual exchange of the three pairs of protons between two equally populated conformers. The Arrhenius and transition state parameters were determined from the rate constants obtained over a temperature range of -5°C to 93°C for a 5 mol% solution of HCOX in methyl- On a effectut, en faisant appel a une analyse de la forme des raies en resonance magnttique nucltaire dynamique complCmentte par une technique de transfert de saturation de double rtsonance homonucltaire, une etude par resonance rnagnttique nucltaire du proton a haute rtsolution de la rotation empechte des groupes dichlororntthyles en fonction de la temperature dans des a,a,a',a',3,4 (7) have previously studied the hindered rotation in a series of o-bis(dich1oromethyl) benzenes, including HCOX in tetradecane, using the variation of the line width of the coalescing resonances as a function of temperature (7). Because the results for H C O X were somewhat ambiguous using this technique the activation parameters were not

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