Proton NMR in nematic liquid crystalline solvents: The use of deuterium decoupling

Nuclear magnetic resonance spectra of molecules dissolved in an oriented (nematic) solvent become exceedingly complex when the solute molecules contain more than about eight magnetic nuclei. In this paper a technique for greatly simplifying the proton spectra by partial deuterium substitution is described. The deuterium is decoupled by irradiation at a frequency corresponding to a double quantum deuteron transition. Experimental details are presented, as well as results obtained on partially deuterated cyclohexane. The behavior of the spectra as a function of deuterium irradiation intensity and frequency offset is shown in a series of experimental spectra, and compared with computer simulated spectra calculated with a theory presented in a companion paper. It is shown that the spectrum behavior under frequency offset of the irradiation can be a tool in the assignment of spectrum peaks.