The crystal and molecular structure of biphenyl
The crystal and molecular structure of biphenyl
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联苯的晶体和分子结构
DOI：
10.1107/s0365110x62000894
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发表时间：
1962
期刊：
影响因子：
--
通讯作者：
S. H. Rizvi
中科院分区：
文献类型：
--
作者：
A. Hargreaves;S. H. Rizvi
用二维（@ o-@ c）图测定了联苯的晶体结构。在实验结果的误差范围内，整个分子是完美的平面。连接两个苯环的键长很长（1.506/~，估计标准偏差为0.017 A），表明环之间没有共轭;这表明分子间力是环占据共面构型的原因。有迹象表明，邻位氢原子之间的空间相互作用导致这些原子从它们在具有120个键角的理想平面分子中占据的位置移位。联苯分子的立体化学（图5（a））一直是许多实验和理论研究的主题（Wheland，1955），但许多结果仍然需要澄清。一般认为，该分子在固相中是平面的，在气相中是非平面的（Coulson，1958）;液相和溶液中的分子构型并不确定（参见，例如，Dale，1957; Katon & Lippincott，1959）。电子衍射研究（Brockway & Karle，1944; Bastiansen，1949; Almenningen & Bastiansen，1958）提供了两个苯环在气相中不共面的证据，最新数据表明，两个苯环以约42 °的角度相互倾斜。认为分子在固相中是平面的观点主要基于X射线证据（Hengsten-berg & Mark，1929; Clark & Pickett，1931;达尔，1932，1949; Kitaigorodsky，1946），这表明晶体是单斜晶系，空间群P21/a，并且晶胞包含两个分子。如果这个证据被接受，那么分子必须位于对称中心上，并且每个分子中的两个苯环必须是共面的，或者非常接近共面的（氢原子He和H~之间的空间相互作用可能会产生小的分子扭曲，而不会破坏分子的对称中心，导致偏离完美的平面性）。只有达尔和Kitaigorodsky尝试了详细的结构分析，他们的结果支持联苯分子在固相中是平面的观点。但是Kitaigorodsky没有发表任何证据来证明他的结果，而达尔的结果是基于试错法，并且非常不准确-唯一的投影的差异因子R是43%，[010]，他使用精确的X射线数据进行了检查。目前的研究联苯已进行，以审查比以前更严格的X射线证据的平面性的分子在结晶相，并获得更准确的
The crystal structure of biphenyl has been determined using two-dimensional (@ o-@ c) maps. The whole molecule is perfectly planar within the limits of error of the experimental results. The great length of the bond linking the two phenyl rings (1.506/~ with estimated standard deviation 0.017 A) indicates that there is no conjugation between the rings; it is suggested that intermolecular forces are responsible for the rings taking up the coplanar configuration. There are indications that steric interactions between the ortho-hydrogen atoms lead to displacements of these atoms from the positions they would occupy in an ideal planar molecule with 120 bond angles.1. Introduction The stereochemistry of the biphenyl molecule (Fig. 5 (a)) has been the subject of numerous experimental and theoretical studies (Wheland, 1955) but many of the results still require clarification. It is generally believed that the molecule is planar in the solid phase and non-planar in the vapour phase (Coulson, 1958); the molecular configurations in the liquid phase and in solution are not known with certainty (see, for example, Dale, 1957; Katon & Lippincott, 1959). Evidence that the two phenyl rings are not coplanar in the vapour phase is provided by electron-diffraction studies (Brockway & Karle, 1944; Bastianssen, 1949; Almenningen & Bastianssen, 1958) with the most recent data indicating that the rings are mutually inclined at an angle of about 42. The belief that the molecule is planar in the solid phase is based largely on X-ray evidence (Hengsten-berg & Mark, 1929; Clark & Pickett, 1931; Dhar, 1932, 1949; Kitaigorodsky, 1946), which indicates that the crystals are monoclinic, space group P21/a, and that the unit cell contains two molecules. If this evidence is accepted then the molecules must lie on symmetry centres and the two phenyl rings in each molecule must be coplanar, or very nearly coplanar (steric interactions between the hydrogen atoms He and H~ may possibly produce small molecular distortions which, without destroying the molecular centre of symmetry, cause deviations from perfect planarity). Only Dhar & Kitaigorodsky have attempted detailed structural analyses and their results support the view that the biphenyl molecule is planar in the solid phase. But Kitaigorodsky has not published any evidence for his results whilst Dhar's results are based on trial-and-error methods and are very inaccurate--the discrepancy factor R is 43% for the only projection,[010], which he examined using accurate X-ray data. The present study of biphenyl has been undertaken in order to examine more critically than previously the X-ray evidence for the planarity of the molecule in the crystalline phase and to obtain more accurate