Molecular structure of crude beeswax studied by solid-state 13C NMR

Abstract

13 C Solid-state NMR experiments were performed to investigate the structure of beeswax in the native state (crude beeswax) for the first time. From quantitative direct polarization 13 C MAS NMR spectrum, it was found that the fraction of internal-chain methylene (int-(CH 2)) component compared to other components of crude beeswax was over 95%. The line shape of the int-(CH 2) carbon resonance region was comprehensively analyzed in terms of NMR chemical shift. The 13 C broad peak component covering from 31 to 35ppm corresponds to int-(CH 2) carbons with trans conformation in crystalline domains, whereas the sharp signal at 30.3 ppm corresponds to gauche conformation in the non-crystalline domain. From peak deconvolution of the aliphatic region, it was found that over 85% of the int-(CH 2) has a crystal structure and several kinds of molecular packing for int-(CH 2), at least three, exist in the crystalline domain.