Inequivalence Magnetique Due a la Presence d'un Atome de Phosphore Asymetrique ou Pseudo-Asymetrique

In phosphinous esters of general formula R? PH(O)OR', the asymmetric phosphorus atom induces magnetic non-equivalence in geminal protons and methyl groups. When alkoxy groups also possess an asymmetric carbon, the presence of the two possible diastereoisomers in equal amounts is proven by ³¹P and ¹H NMR. ³¹P NMR reveals that the phosphorus atom in phosphonous esters R? P(O·C₄H₉-s)₂ of racemic sec. butyl alcohol, is a centre of pseudo-asymmetry.