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单词 Axial chirality
释义

Axial chirality

中文百科

轴手性

R and S 标记根据轴向观察时四个基团的排布按照串行法则决定
P helicityM helicity螺旋命名示意(以七螺苯为例,其中P表示右旋,M表示左旋

轴手性是手性的一种特殊情形。一般情况下,有机分子的手性是由于手性中心而产生的,但在轴手性的情况下,分子内没有手性中心而是有一根手性轴。多个基团围绕轴排布,其排布方式使得分子无法与其镜像重合。轴手性最常见于旋转受限的不对称联芳环(如联苯)类化合物中,如 1,1'-联(2-萘酚)。 一些丙二烯类化合物也会显示出轴手性。轴手性化合物的对映异构体通常用立体化学的标记 Ra 与 Sa.表示。具体规则与含有手性中心的化合物类似。在确定立体化学的具体字母时,视线从手性轴的一端沿手性轴的方向观察,定出两个靠近观察者的基团和两个远离观察者的集团,再依照串行法则比较各基团的大小。下面给出了一些例子。

英语百科

Axial chirality 轴手性

R and S configurations are determined by precedences of the groups attached to the axial section of the molecule when viewed along that axis.
P helicityM helicityConfigurations of heptahelicene

Axial chirality is a special case of chirality in which a molecule does not possess a stereogenic center (the most common form of chirality in organic compounds) but an axis of chirality – an axis about which a set of substituents is held in a spatial arrangement that is not superposable on its mirror image. Axial chirality is most commonly observed in atropisomeric biaryl compounds wherein the rotation about the aryl-aryl bond is restricted, for example, biphenyl, binaphthyls, e.g., 1,1'-bi-2-naphthol, and certain dihydroanthracenone compounds. Certain allene compounds and spirans also display axial chirality. The enantiomers of axially chiral compounds are usually given the stereochemical labels Ra and Sa. The designations are based on the same Cahn-Ingold-Prelog priority rules used for tetrahedral stereocenters. The chiral axis is viewed end-on and the two "near" and two "far" substituents on the axial unit are ranked.

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更新时间:2025/6/18 10:45:17