分子手性的温度效应：D-丙氨酸的变温X衍射与中子衍射研究.pdf

物理化学学报( 怎造蚤 匀怎葬曾怎藻 载怎藻遭葬燥) 774 粤糟贼葬孕澡赠泽援鄄悦澡蚤皂援杂蚤灶援熏 园园缘, 圆员(7) 774耀781 July Temperature Effect on Molecular Chirality X鄄ray Diffraction * and Neutron Diffraction Studies of D鄄alanine WANG, Wen Qing GONG, Yan YAO, Nan (Department of App lied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beiji ng 100871) Abstract The results of X ray diffraction of single crystal D and L alanine at 300, 270, 250 K and neutron diffraction of D alanine at 300, 260, 250, 240 K were presented to look for the static and dynamical structure feature of Salam phase transition. No change in the space group P2 2 2 symmetry was observed. The data rule out the hy 1 1 1 pothesis of a conventional structural phase transition and reveal a subtle and continuous symmetry breaking that oc curs below ~250 K. A vibrationally generated electronic ring current model was exp lained the temperature effect on magnetic susceptibilities and opposite optical rotation phenomena related to the bond lengths of C-H(2), N(1)-H(1), N (1)-H (4), and N (1)-H (6) lengthening (or contraction). A picture of dynamic disorder due to the protonic motion was presented in the intermolecular hydrogen bonds between the NH + group and the CO- group. Salam predicted the 3 2 enhancement of parity violating e