Nuclear Magnetic Resonance Studies of Some 1,1-Difluoro-3-Phenylcyclobutane Derivatives

Citation

Takahashi, Masaaki (1962) Nuclear Magnetic Resonance Studies of Some 1,1-Difluoro-3-Phenylcyclobutane Derivatives. Master's thesis, California Institute of Technology. doi:10.7907/481A-5Q94. https://resolver.caltech.edu/CaltechTHESIS:05062010-112117806

Abstract

1-Difluoro-2, 2-dichloro-3-methy1-3-phenylcyclobutane has been prepared by the cycloacidition of a-methylstyrene to 1,1-difluoro2, 2-dichloroethylene. A 2 cps long-range H-F spin-spin coupling has been observed over five consecutive saturated bonds in 1,1-difluoro2, 2-dichloro-3-methyl-3-phenylcyclobutane, involving one of the fluorines at the 1-position and the protons of the 3-methyl group. Analysis of the spectrum and that of the stereospecifically labeled 4-deutero derivatives suggest that the fluorine involved is the one cis to the methyl group. The n. m. r. studies of 1,1-difluoro-3-bromo-3-phenylcyclobutane which was obtained by bromination of 1,1-difluoro-3-phenylcyclobutane with N-bromosuccinimide indicate that this molecule has on the average a more nearly planar cyclobutane ring than that of 1,1- difluoro-2, 2-dichloro-3-methyl-3-phenylcyclobutane. The four protons of the 2- Etna 4-positions are nearly magnetically equivalent, so that the spectrum of this compound is almost that of an ABX_4 system rather than an ABX_2Y_2 system. The theoretical calculations suggest that the chemical shift difference between X and Y is on the order of 1-2 cps. The chemical shift difference between the fluorines decreases in 1,1-difluoro-2, 2-dichloro-3-methy1-3-phenylcyclobutane and 1,1- difluoro-3-bromo-3-phenylcyclobutane with increasing temperature, suggesting that rapid ring-inversion is taking place.

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