A 19F NMR STUDY OF THE HYDROLYSIS OF ORGANOPHOSPHORUS FLUORIDATES IN AQUEOUS SOLUTION Doubling of the 19F nmr in Diastereoisomeric Mixtures

Abstract

¹H and ¹⁹F nmr spectra of two series of organophosphorus esters containing a P–F bond were studied. 2-Fluoro-4-methyl 1,3,2-dioxaphosphorinane 2-oxide (2) was found to be a mixture of two diastereoisomers in the ratio of trans/cis = 4.

Stereospecific catalysis of phosphate and maleate anions in the hydrolysis of 2 was observed, leading to enrichment of the non-hydrolysed fluoridates with the trans isomer.

The ¹⁹F nmr spectra of O-2-butyl methylphosphonofluoridate (7) and O-pinacolyl methylphosphonofluoridate (8), showed doubling of the ¹⁹F nmr spectra, giving rise to two sets of double quartets of equal intensity. 1:1 mixtures of diastereoisomers account for the doubling of the resonance rather than sterically hindered rotation. The applicability of nmr spectroscopy to the study of stereospecific displacement reactions at tetrahedral phosphorus is discussed.