Nuclear Magnetic Resonance Spectroscopy. Analysis and Temperature Dependence of the Spectra of Cycloheptatriene and 7,7-Bistrifluoromethylcycloheptatriene

Abstract

Complete analyses of the room-temperature proton spectra of cycloheptatriene (I) and its 7,7-bistrifuoromethyl derivative (II) have been achieved. Whereas the methylene protons of I are nonequivalent below about -140º, the trifluoromethyl groups in II remain equivalent on the n.m.r. time scale down to -185º. An explanation for this behavior is sought in the differences in the magnitudes of the vicinal coupling constants (J_(23)) of I and II. There is no change in any of the coupling constants of I over the temperature range from -70 to +115º. The n.m.r. evidence therefore gives no indication of the presence of norcaradiene in equilibrium with cycloheptatriene.

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