CHEMICAL SHIFT NON-EQUIVALENCE IN THE NMR SPECTROSCOPY OF DIALKYL<i>α</i>-HYDROXYBENZYL-AND DIALKYL<i>α</i>-METHOXYBENZYLPHOSPHONATES AND THE CRYSTAL STRUCTURE OF DIMETHYL<i>α</i>-CHLOROMETHYL-<i>α</i>HYDROXYBENZYLPHOSPHONATE

Abstract

Abstract Single crystal X-ray diffraction of dimethyl α-chloromethyl-α-hydroxybenzylphosphonate shows the compound to exist as hydrogen-bonded dimers in the solid state. In solution, 1H and 13C nmr spectroscopy reveal chemical shift non-equivalence of the corresponding nuclei in the two alkoxy groups of dialkyl α-hydroxybenzyl-and dialkyl α-methoxybenzylphosphonates, an effect that is attributed primarily to the presence of the chiral α-carbon atom, although restriction of rotation about the P—C α bond by intermolecular hydrogen-bonding may also be a factor in the α-hydroxy compounds. Chemical shift non-equivalence of the α-halogenomethyl protons in dimethyl α-halogenomethyl-α-hydroxyben-zylphosphonates is significantly greater for the chloro-than for the bromo-compound.