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为了解决D-和L-缬氨酸单晶在～270 K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0.18 J·mol-1.本文以Mo-Kα(λ=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～270 K,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(trans)和B(gauche I).温度为293、270、223、173 K的X衍射精细结构数据表明:在～270 K,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-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270-290 K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.
In order to resolve the mechanism and the bifurcation of D-and L-valine single crystals at ~ 270 K phase transitions, single-crystal, polycrystalline powders and Sigma polycrystalline products were determined by the specific heat method. Only D- and L-valine The phase transition of single crystal and its endothermic reaction, with a difference of 0.18 J · mol-1.The accurate determination of X-ray diffraction with Mo-Kα (λ = 0.071073nm) The crystals belong to the group of monoclinic space points P21 and Z = 4. The lattice constants at a phase transition temperature of ~ 270 K are: a = 0.96706 (5) /0.96737 (5) nm and b = 0.52680 (3) /0.52664 3) nm, c = 1.20256 (7) /1.20196 (6) nm, β = 90.724 (2) ° / 90.722 (3) ° In the unit cell of the crystal structure, two kinds of rotamers are contained: A ) And B (gauche I). The X-ray diffraction fine structure data at 293, 270, 223 and 173 K show that in the N-H ... O hydrogen bond of D-valine mono- -H, H ... O bond length and bond angle ∠N-H ... O fluctuations are unpredictable, but the N-H ... O total bond length change is stable and can be measured .There is no configuration phase transition to L- Valine According to the clockwise and counterclockwise opposite directions of NH3 → CO2 and the determination of the rotation angles of D-, L- and DL-valine crystals in D- and L-valine single crystals, K To observe the interstitial molecules N + H ... electron spin current superconducting Cooper pairs O- hydrogen phase transition.