PMR spin lattice relaxation by reorientational motions of NH3 and CH3 groups in some organic compounds

The spin-lattice relaxation times, T₁, of protons in o, m, p-phenylene-diamine dihydrochlorides C₆H₄(NH₂)₂·2HCl, phenylhydrazinium chloride C₆H₅NHNH₃Cl, hexaethylbenzene C₆(CH₂CH₃)₆, tetrabutylammonium bromide CH₃(CH₂)₃]₄NBr, iodide CH₃(CH₂)₃]₄NI, tetraheptylammonium bromide CH₃(CH₂)₆]₄NBr and iodide CH₃(CH₂)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 ?NH₃⁺ and ?CH₃ groups about C₃ 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 T₁, 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 ?NH₃⁺ or ?CH₃ protons. Therefore it has been concluded that the T₁, minima of ?NH₃⁺ and ?CH₃ groups, when obtainable can indicate their number present in a solid sample.