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The l H n.m.r. spectra of optically active (but optically impure) samples of methylphenylphosphinic amide (3) and its N-phenyl (1) and N-p-nitrophenyl (2) analogues exhibit distinct signals for the P-methyl groups in the R-and S-enantiomers. The two enantiomers in a racemic sample of ( I ) , (2). or (3) give rise to only one Pmethyl resonance, but this separates into two distinct signals when a foreign optically active phosphinic amide is added. Similar enantiomer non-equivalence can be induced in racemic samples of phenyl-t-butylphosphinic amide ( 6) and (N-pheny1)phenyl-t-butylphosphinic amide (7). while the enantiotopic methyl groups in (N-pheny1)dimethylphosphinic amide (8) or dimethylphosphinic amide (9) become non-equivalent in the presence of optically active (1). The observed spectra can all be rationalised in terms of molecular association through hydrogen bonding. However, as UskokoviC and his colleaguesRES WLTS AND DISCUSSION Nixtwes of Optically Active and Racemic Phosplzircic Amides of Like Strwture.-The lH n.m.r. spectrum of enantiomerically pure (S)-( 1) in CDC1, ( 0 . 2 3 ~ solution) includes a doublet (IPH 13.6 Hz) at 6 1.74 attributable to the P-methyl group. Addition of racemic ( l ) , as a solution ( 0 . 2 3 ~) in CDCl,, in the amount t We are grateful to Professor H. Wynberg for bringing this work to our notice.

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