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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >The unusual phases of anhydrous and hydrated pinacol
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The unusual phases of anhydrous and hydrated pinacol

机译：无水和水合频哪醇的不寻常相

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摘要

The structure of highly twinned pinacol (2,3-dimethyl-2,3-butanediol) monohydrate, the existence of which has been known since 1922, has been determined, and the structures of anhydrous pinacol and its two other known hydrates have been reinvestigated. All the phases are unusual. The anhydrous phase [Jeffrey & Robbins (1978). Acta Cryst. B34, 3817-3820] is exceptional among molecular crystals in having molecules located on three different symmetry sites (1, (1) over bar and 2). A hexagonal form of pinacol originally described as a second polymorph [Dahlqvist & Sillanpaa (2000). J. Mol. Struct. 524, 141-149] has been shown to be a solvate of uncertain composition that is very loosely packed. Pinacol hexahydrate, which was originally reported as tetragonal and highly disordered [Kim & Jeffrey (1970). J. Chem. Phys. 53, 3610-3615], appears to be described better as having an orthorhombic structure that is both disordered and twinned; the diffraction pattern at 90 K shows structured diffuse scattering that suggests short-range correlations of disordered molecules. The occurrence of this unusual set of structures is attributed to the combination of the hydrogen-bonding requirements of the pinacol molecule with its small size and limited conformational flexibility.
机译：自1922年以来就已知存在高度孪生的频哪醇（2,3-二甲基-2,3-丁二醇）一水合物的结构，并确定了无水频哪醇及其两种其他已知水合物的结构。 。所有阶段都不正常。无水相[Jeffrey＆Robbins（1978）。 Acta Cryst。 [B34，3817-3820]在分子晶体中是例外的，因为分子位于三个不同的对称位点上（条形上的1，（1）和2）。频哪醇的六边形形式最初描述为第二种多晶型物[Dahlqvist＆Sillanpaa（2000）。 J.摩尔结构。 [524，141-149]已证明是一种不确定的溶剂化物，其包装非常松散。六水合频哪醇，最初被报道为四方晶且高度无序[Kim＆Jeffrey（1970）。 J.化学物理53，3610-3615]，似乎被更好地描述为具有既无序又孪生的正交结构; 90 K时的衍射图显示出结构化的散射，表明无序分子的短程相关性。这种不寻常的结构集的出现归因于频哪醇分子的氢键结合要求以及其小尺寸和有限的构象柔韧性。

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