Studies of chemical-shift anisotropy in liquid-crystal solvents. I. Experimental results for the methyl halides

Abstract

Analysis of the nuclear magnetic resonances of the methyl halides dissolved in nematic-liquid-crystal solutions has given measurements of the anisotropy of the proton chemical shift. The accurate determination of these anisotropies is made difficult by the effect of the liquid-crystal solvent on the chemical-shift measurements. The method was found to be unsuitable for the measurement of the methyl fluoride anisotropy, but the values for the other methyl halides have been determined to within ±1.5 ppm. Methyl chloride and methyl bromide are found to have small proton chemical-shift anisotropies indistinguishable from zero, and methyl iodide appears to have a small positive anisotropy.