The 1 H spin lattice relaxation times of the proton bearing groups and the 31 P spin lattice relaxation times in C phosphorylated oximes R 1 C(=NOH)P(=O)R 2 R 3 (R 1 = Ph, R 2 = R 3 = OMe; R 1 = Ph, R 2 = OMe, R 3 = OCH 2 CH 2 Br; R 1 = PhCH 2 , R 2 = R 3 = OCHMe 2 ) and dioxime R 2 P(=O)C(=NOH)(CH 2 ) 4 C(=NOH)P(=O)R 2 (R = OMe) in DMSO d 6 were measured. The characteristic reorientation times of the whole molecules were estimated using the measured values of the 1 H relaxation times and the results of semiempirical PM3 quantum chemical calculations of the molecular geometries. The reorientation times were used to identify the contributions of different relaxation mechanisms to the rate of 31 P spin lattice relaxation. The anisotropy of the chemical shielding of 31 P nuclei was evaluated from the difference between the 31 P relaxation rates measured at 101.27 and 161.92 MHz.Oximes are widely used in synthetic, analytical, and coordination chemistry as pharmaceuticals and antidots, plant growth regulators, sources of iminoxyl free radicals, etc. 1-6 Among various groups of oximes, an important role is played by phosphorus containing oximes. Increas ing interest in these compounds is due to the extension of synthetic potential provided by phosphorus containing substituents (see, e.g., Ref. 5) and to the fact that many of them are biologically active (insecticides, phosphono cefems, etc.). 4 Phosphorylated oximes are of particular interest be cause the iminoxyl radicals generated from them show the interaction of the phosphorus atom with the radical cen ter, 6-8 which depends on their mutual arrangement. In this connection, considerable attention was paid to studies of the molecular and electronic structures of C phosphorylated oximes. 9-14 It was shown that these, like other types of oximes, can exist in solutions as E C=N and Z C=N isomers irrespective of the nature of substitu ents in the phosphorus containing and carbon fragments. Usually, Z C=N isomers of the α phosphorylated oximes are stabilized by the intramolecular hydrogen bond P=O ... HO. This results in flattening of the phosphoryl imine oxime fragment of the molecule and to an increase in the barrier to internal rotation about the =C-P= bond (an increase in the "rigidity" of the phosphoryl hydroxy imine fragment).Parameters of the 31 P, 13 C, and 1 H NMR spectra of the isomers are noticeably different. 9-14 The most stereo dependent are the direct ( 1 J P,C ), geminal ( 2 J P,C ), and vicinal ( 3 J P,C ) spin spin coupling constants.Application of nuclear magnetic relaxation spectro scopy to the solution of structural chemistry problems allows one to assess not only the molecular structure and conformations, but also the dynamics of the whole mol ecule and its fragments. In the present work, we report the results of a study on the mechanisms of 31 P and 1 H nuclear spin lattice relaxation and on the parameters of their mag E Isomer Z Isomer
