A detailed NMR investigation, supported by DSC and X-ray diffraction measurements, of the combwax of the African bee apis mellifera adansonii is reported. Proton spin-lattice relaxation times in the laboratory and rotating frames, as well as the proton spin-spin relaxation time, have been measured as a function of temperature (333 K>T>110 K). The liquid content of the wax has also been determined as a function of temperature by employing a simple pulse technique. The motional parameters associated with the reorientations of the methyl groups and the chains have been isolated and compared with these parameters for similar motions in Fischer-Tropsch waxes. The T1 rho results revealed a minimum which is associated with the dangling motion of chain ends in the amorphous zone of the wax. The relaxation results strongly suggest that beeswax is branched to a much higher degree than Fischer-Tropsch waxes, including oxidised waxes. The high-resolution 13C spectrum of beeswax in the solid state shows that it resembles oxidised Fischer-Tropsch hard wax closely. The major difference is that a higher percentage of carbon atoms are involved in ester groups in beeswax. Oxidised hard wax contains a higher fraction of carbon atoms with double carbon-carbon bonds. The average chain length in beeswax, determined by ebullioscopic methods, is 40 carbon atoms.
For pt.I see ibid., vol.21, p.1421 (1988). Structural aspects and the molecular dynamics of carnauba wax are reported. X-ray diffraction results show that it crystallises in an orthorhombic unit cell. DSC and proton spin-lattice measurements as a function of temperature revealed a premelting solid-solid transition at 335 K. The percentage of carbon atoms in methyl and methylene groups is approximately 12% less than in beeswax, whereas it has a much higher ester and carbonyl content. The average chain length in carnauba wax is 50 carbon atoms. Spin-spin relaxation measurements revealed that the reorientational-translational motion of the chains is much more hindered than in beeswax. The motional parameters associated with the reorientations of the methyl groups have been isolated and compared with these parameters for similar motions in Fischer-Tropsch waxes and beeswax. Spin-lattice relaxation measurements in the rotation frame showed that the activation energy for the dangling motion of the chain ends is approximately 20% higher than in beeswax. The liquid content of the wax has also been determined as a function of temperature by employing a simple pulse technique.
The crystal structures and molecular dynamics of solution-grown and melt-grown polycrystalline samples of n-hexatriacontane have been investigated by employing NMR, DSC and X-ray powder diffraction techniques. All solution-grown samples have the same orthorhombic structure, while the melt-grown samples are mixtures of a monoclinic and two orthorhombic structures. Defect motions of chain ends between all-trans and defect orientations are present in all crystal modifications at room temperature, but defect orientations have significantly higher populations in the orthorhombic structure which occurs only in the melt-grown sample.
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