中文摘要：

为了解决D-和L-缬氨酸单晶在-270K相变的机理和分岐，以比热法测定单晶、多晶粉末及Sigma多晶产品发现，只有D-和L-缬氨酸单晶发生相变，且为吸热反应，能差0．18J·mol^-1．本文以Mo-K.（A=0．071073nm）为光源的X衍射精确测定表明，D-/L-缬氨酸单晶属于单斜空间点群P21，Z=4．在相变温度-270K，其晶格常数分别为：a=0．96706（5）／0．96737（5）nm，b=0．52680（3）／0．52664（3）nm，c=1．20256（7）／1．20196（6）nm，β=90．724（2）°／90．722（3）°．在晶体结构的单元细胞中，含有两种转动异构体：A（frans）和B（gaucheI）．温度为293、270、223、173K的X衍射精细结构数据表明：在-270K，D＊缬氨酸单晶分子内N—H…O氢键中，N—H、H…O的键长及键角∠N—H…O都发生波动起伏而不可测，但N—H…O总键长变化稳定可测．说明没有发生构型相变为L一缬氨酸．根据D-和L-缬氨酸单晶中，NH3→CO2顺时针和逆时针的相反走向及D-，L-和DL-缬氨酸晶体旋光角的测定，在270—290K可以观察到晶格分子间N’H…O-氢键电子库珀对的自旋流超导相变．

英文摘要：

With a view to understanding the argument of the phase transition mechanisms of D- and L- valine around 270 K, the temperature dependences of the heat capacities of single crystals, ground powders, and polycrystalline products were investigated using differential scanning calorimetry. Endothermic transition peaks were observed at phase transition temperatures of 273.59 and 273.76 K for D- and L-valine single crystals, respectively with an energy difference of 0.18 J o mo1-1. The X-ray crystal fine structure of chiral valine was determined using Mo-Ko radiation （3 =0.071073 nm） on Nonius Kappa CCD diffractometer. D- and L-valine crystals were monoclinic, with the P21 space group, Z=4, lattice constants a= 0.96706（5）/0.96737（5） nm, b=0.52680（3）/0.52664（3） nm, and c=1.20256（7）/1.20196 （6） nm, and ,8=90.724（2）°/ 90.722（3）° at -270 K. Two crystallographically independent molecules A （trans form） and B （gauche I from） were observed in the unit cell, these were rotational isomers with two different conformations. X ray diffraction at 293, 270, 223, and 173 K showed that the N--H, H--O bond lengths and the N--H...O bond angle of D-valine fluctuated at 270 K, but the intramolecular N--H...O hydrogen bond was stable and measurable. No evidence was obtained for a configuration transformation from D-valine to L-valine. Based on the clockwise and counterclockwise rotations of NH3→CO2 in the chiral valine crystals and the optical rotatory angle measurements, the intermolecular N~H.--O- hydrogen bond was electronic Cooper pairing and exhibited the spin superfluidity onto D-, L-, and DL- valine crystal lattices from 270 to 290 K upon the transition to the superconducting state.