Conversion in the solid state of the yellow to the red form of 2-(4'-methoxyphenyl)-1,4-benzoquinone. X-ray crystal structures and anisotropy of the rearrangement
Conversion in the solid state of the yellow to the red form of 2-(4'-methoxyphenyl)-1,4-benzoquinone. X-ray crystal structures and anisotropy of the rearrangement
复制标题
黄色固态转化为红色形式的 2-(4-甲氧基苯基)-1,4-苯醌。
DOI：
10.1021/ja00447a051
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发表时间：
1977
影响因子：
15
通讯作者：
D. Curtin
中科院分区：
文献类型：
--
作者：
G. Desiraju;I. Paul;D. Curtin
本文研究了2-（4′-甲氧基苯基）- 1,4 -苯醌在固体状态下由黄色（la）晶体向红色（lb）晶体的热重排。单晶通过一个过程重新排列，该过程从晶体中有限数量的成核位置开始，并通过明确定义的前沿迁移而扩散。测定了la和lb的x射线晶体结构。la的黄色晶体为正交晶型，a= 6.719 (2), b= 7.168 (3), c= 44.206 (18) a；空间群为Pbca，在1473次非零反射上，结构被细化到R因子为0.043。红色形式lb是正交的，a= 12.783 (2), b= 6.969 (2), c= 23.369 (5) a；空间群为Pbca，在1530次非零反射下，该结构的R因子为0.052。这些结构都是由外消旋对分子组成的，由于两个六元环的非平面排列，一个特殊的分子是手性的。黄色和红色组成分子作为非对映异构体相互关联。颜色上的差异是由相邻醌环之间重叠的黄色形式的分子堆叠造成的，而在红色形式中，醌和反基环之间存在rr络合。正如所预料的那样，这种络合会导致红色形式中键距的一些改变。
The thermal rearrangement in the solid state of the yellow (la) to the red (lb) crystalline form of 2-(4'-methoxyphenyl)-l, 4-benzoquinone has been studied. Single crystals rearrange by a process which begins at a limited number of nuclea-tion sites in the crystal and spreads by migration of well-defined fronts. X-ray crystalstructures of la and lb have been determined. The yellow crystals of la are orthorhombic, a= 6.719 (2), b= 7.168 (3), c= 44.206 (18) A; the space group is Pbca, and the structure has been refined to an R factor of 0.043 on 1473 nonzero reflections. The red form lb is orthorhombic, a= 12.783 (2), b= 6.969 (2), c= 23.369 (5) A; the space group is Pbca, and the structure has been refined to an R factorof 0.052 on 1530 nonzero reflections. The structures are each composed of racemicpairs of molecules, a particular moleculebeing chir-al by virtue of the nonplanar arrangement of the two six-membered rings. Theyellow and the red constituent molecules are re-lated to each other as diastereoisomers. The difference in the color is accounted for by the stacking of the molecules in the yellow formwith overlapbetween adjacent quinone rings, whereas in the red form there is rr complexing between quinone and ani-syl rings. As might have been anticipated, this complexing leads to some alteration of bond distances in the red form.