13C solid-state NMR analysis of heterogeneous structure of beeswax in native state

I investigated the molecular structure of natural wax from Japanese bees ( Apis cerana japonica ) in its native state (neither purified nor recrystallized) by 13 C and 1 H solid-state NMR. Two strong 13 C peaks at 32.9 and 34.0 ppm were attributed to signals from internal-chain methylene carbons [int-(CH 2 )] in two types of crystal form. The peak at 32.9 ppm was assigned to an orthorhombic crystal form, and that at 34.0 ppm was assigned to a triclinic or monoclinic form. In both crystalline regions, bi-exponential decay of 13 C spin-lattice relaxation [ T 1 (C)] for the crystalline peaks due to chain diffusion was observed. 1 H spin-lattice relaxation [ T 1 (H)] values for protons of the CH 3 group and for int-(CH 2 ) in the crystalline and amorphous regions were identical; this was interpreted as being due to averaging of the T 1 (H) relaxation rates via spin diffusion. In contrast, although the decay curves for protons of the CH 3 group and for int-(CH 2 ) in the amorphous and orthorhombic forms were almost identical, those of the triclinic or monoclinic forms were different. This unhomogeneous character of was interpreted as resulting from differences in the molecular composition of each crystal form. Moreover, two components with long and short 1 H spin–spin relaxation [ T 2 (H)] values, arising from the mobile and rigid phases, respectively, were observed at above about −30 °C.