Kolesov B A, Boldyreva E V
Institute of Inorganic Chemistry, SB RAS, Lavrent'eva 3, Novosibirsk 630090, Russia.
J Phys Chem B. 2007 Dec 27;111(51):14387-97. doi: 10.1021/jp076083o. Epub 2007 Dec 4.
Single-crystal polarized Raman spectra (60-4000 cm(-1) at 3 < or = T < or = 295 K) were measured for chiral L- and racemic DL-serine, alpha-amino-beta-hydroxypropionic acid, (NH3)+CH(CH2OH)(COO)-. The Raman spectra of dl-serine do not show any striking changes with temperature or on storage. In contrast to that, the dynamical properties of L-serine change at about 140 K. These changes can be interpreted as the reorientation of the side chain -CH2OH fragments of the zwitterions with respect to the backbone C-C bonds, resulting in the positional disorder of the O-H...O intermolecular H-bonds. The redistribution in the intensities of the Raman spectra of the crystals of L-serine stored for a long time (about a year) indicates the changes in the orientation of the molecular fragments in the direction normal to the axes of the head-to-tail chains. The difference in the thermodynamic functions of L- and DL-serine reported previously [Drebushchak, V. A.; Kovalevskaya, Yu. A.; Paukov, I. E.; Boldyreva, E. V. J. Therm. Anal. Calorim. 2007, 89 (2), 649-654] is explained by the difference in the spectra of external vibrations of the crystals.
对手性L-丝氨酸和外消旋DL-丝氨酸（α-氨基-β-羟基丙酸，(NH3)+CH(CH2OH)(COO)-）测量了单晶偏振拉曼光谱（在3≤T≤295K时为60 - 4000cm(-1)）。DL-丝氨酸的拉曼光谱在温度变化或储存时未显示出任何显著变化。与此相反，L-丝氨酸的动力学性质在约140K时发生变化。这些变化可解释为两性离子的侧链-CH2OH片段相对于主链C-C键的重新取向，导致O-H...O分子间氢键的位置无序。长时间（约一年）储存的L-丝氨酸晶体拉曼光谱强度的重新分布表明分子片段在垂直于头对头链轴方向上的取向发生了变化。先前报道的[Drebushchak, V. A.; Kovalevskaya, Yu. A.; Paukov, I. E.; Boldyreva, E. V. J. Therm. Anal. Calorim. 2007, 89 (2), 649 - 654]L-丝氨酸和DL-丝氨酸热力学函数的差异是由晶体外部振动光谱的差异所解释的。
