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信源：https://journals.iucr.org/c/services/cif/hbonds.html | Descriptions and discussion of weak and non-conventional hydrogen bonds (C-H...X, X-H...C and C-H...C) need not always parallel what is accepted for the stronger and more conventional types of hydrogen-bond interactions (X-H...X). The following may be noted: | 弱氢键和非常规氢键（C-H...X、X-H...C和C-H...C）的描述和讨论不必总是平行于更强和更常规类型的氢键相互作用（X-H...X）所接受的内容。可能要注意以下几点： |
| (1) The van der Waals criterion for a weak hydrogen bond can sometimes be unnecessarily restrictive. This criterion is without real scientific basis because hydrogen bonds and van der Waals interactions have different distance dependence characteristics. In practical terms this means that a short hydrogen bond formed by an activated C-H donor (chloroform, alkyne or more acidic C-H group) would usually be correctly identified. The problem arises for longer contacts formed by donors of moderate activity. Here, a more detailed look is often necessary and useful. In general, statements like `the contact is shorter than the van der Waals limit and is therefore a hydrogen bond' should be avoided. | （1）弱氢键的范德华判据有时可能具有不必要的限制性。这个标准没有真正的科学依据，因为氢键和范德华相互作用具有不同的距离依赖特性。实际上，这意味着由活化的C-H供体（氯仿、炔烃或酸性更强的C-H基团）形成的短氢键通常会被正确识别。问题出现在由中等活性的供体建立的长接触作用上。在这里，更详细的查看通常是必要和有用的。一般来说，应该避免诸如“接触比范德华极限短，因此是氢键”之类的说法。 |
| (2) Unlike strong hydrogen bonds, the weaker varieties are easily distorted by the crystal environment. Therefore, it is useful to discuss hydrogen-bond lengths and angles jointly. A longer C-H...O contact (D > 3.6 Å) may be acceptable as a hydrogen bond if the angle tends towards linearity (θ > 150°). Very short C-H...O contacts (D < 3.2 Å) with very bent angles (90-110°) should be viewed with some scepticism. In cases of doubt, angular considerations should take precedence over length considerations. | （2）与强氢键不同，较弱的种类很容易被晶体环境扭曲。因此，共同讨论氢键的长度和角度是有用的。如果角度趋于线性（θ > 150°），则较长的C-H...O接触（D > 3.6 Å）可以作为氢键接受。对于具有非常弯曲的角度（90-110°）的非常短的C-H...O接触（D < 3.2 Å），应持怀疑态度。在有疑问的情况下，角度考虑应优先于长度考虑。 |
| (3) Unactivated methyl groups could pose special problems. These are known to sometimes form very short hydrogen-bond-like contacts (perhaps even tending to linearity) but these contacts are most likely repulsive and possibly even destabilising. This situation is, however, uncommon. Methyl groups also form genuine hydrogen bonds. | （3）未活化的甲基可能会带来特殊问题。已知这些有时会形成非常短的类氢键接触（甚至可能趋于线性），但这些接触很可能是排斥性的，甚至可能是不稳定的。然而，这种情况并不常见。甲基也形成真正的氢键。 |
| In summary, the results of commonly used geometry programs should not be transferred directly and routinely into tables without adequate inspection of the molecular and crystal structure. Unqualified statements like `the structure is stabilized by C-H...O hydrogen bonds' should be avoided. The study of weak hydrogen bonds is still evolving. Factors like donor acidity, acceptor basicity, hydrogen-bond length, hydrogen-bond angle and possible co-operativity effects should be assessed (even if they are not commented upon explicitly in the paper). For further information, authors could refer to some of the following: | 总之，在没有对分子和晶体结构进行充分检查的情况下，不应将常用几何程序的结果直接和常规地转移到表格中。应避免诸如“结构由C-H...O氢键稳定”之类的不合格陈述。弱氢键的研究仍在发展中。应评估供体酸性、受体碱性、氢键长度、氢键角和可能的协同效应等因素（即使论文中没有明确评论）。有关更多信息，作者可以参考以下内容： |
(a)Desiraju, G. R. (1991). Acc. Chem. Res.24, 290. (b)Desiraju, G. R. (1996). Acc. Chem. Res.29, 441. (c)Steiner, T. (1996). Crystallogr. Rev.6, 1. (d)Steiner, T. (1997). Chem. Commun.727. (e)Desiraju, G. R. & Steiner, T. (1999). In The Weak Hydrogen Bond in Structural Chemistry and Biology, OxfordUniversity Press. 如需本文文档，请在以下链接下载： （1） 链接：https://pan.quark.cn/s/0040053c66f8 提取码：sF71 （2） 提取码: idpx
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发表于 2025-3-16 07:32:21
