Rotational Motions in n-Hexane Phosphonic Acid Diethyl Ester Studied Combining 2H, 13C, and 31P NMR. Analysis of the Phosphorus-31 Spin-Lattice Relaxation

Article abstract of DOI:10.1016/0022-2364(86)90431-2

Spin-lattice relaxation of 13C and 31P in neat H3C(CH2)5P(O)(OC2H5)2 and of 2H and 31P in H3C(CH2)4C 2H2P(O)(OC2H5)2 and H3C(CH2)5P(O)(OC2 2H5)2 have been measured in the temperature range from - 70 to 160 deg C and at different fields.By using the NOE and the selectivity deuterated compounds the contributions of different segments to the total proton-phosphorus dipole-dipole relaxation were determined.Quantitative analysis of the 31P relaxation yields the result that, at the phosphorus resonance frequencies of 36.44 and 145.76 MHz and at all temperatures studied, at least two interaction mechanisms contribute.Further, the α-CH2 segment, the ester groups, and the hexyl residue without the α-CH2 segment, each gives approximately one-third of the total proton-phosphorus dipole-dipole contribution.The spin-lattice relaxation of 2H, 13C, and 31P is described on the basis of the Woessner model in the whole temperature range studied with one set of motional parameters.The relaxations of the spins in the H2CP(O)O2 and 2H2CP(O)O2 segments are mainly determined by the overall reorientation whereas this motion has at most a small effect on the 13C relaxation of the other segments and on the 2H relaxation of the ester groups.