PMR spin lattice relaxation by reorientational motions of NH 3 and CH 3 groups in some organic compounds

Abstract

The spin-lattice relaxation times, T 1, of protons in o, m, p-phenylene-diamine dihydrochlorides C 6H 4(NH 2) 2·2HCl, phenylhydrazinium chloride C 6H 5NHNH 3Cl, hexaethylbenzene C 6(CH 2CH 3) 6, tetrabutylammonium bromide [CH 3(CH 2) 3] 4NBr, iodide [CH 3(CH 2) 3] 4NI, tetraheptylammonium bromide [CH 3(CH 2) 6] 4NBr and iodide [CH 3(CH 2) 6] 4NI powders have been measured between 400 and 100 K at 60MHz. The experimental results have been explained by considering the reorientational motions of −NH 3 + and −CH 3 groups about C 3 axes and their role of behaving as sinks to rapid spin diffusion of the ring protons of the phenylene and the methylene protons. The observed T 1, minima in all these substances turn out to be the measures of the ratios between the total number of protons and the number of reorienting −NH 3 + or −CH 3 protons. Therefore it has been concluded that the T 1, minima of −NH 3 + and −CH 3 groups, when obtainable can indicate their number present in a solid sample.