Kier L B, Hall L H
J Pharm Sci. 1976 Dec;65(12):1806-9. doi: 10.1002/jps.2600651228.
The molecular connective index, chi, initially designed for hydrocarbons, has been formally extended to molecules containing heteroatoms. The sigma value of the heteroatom is modified to take account of its number of attached hydrogen atoma, sigmaiv = Zv - hi. These values were successfully tested on boiling points and molar refractions. A table of sigmav values is presented for nitrogen, oxygen, fluorine, chlorine, bromine, and iodine in various bonding situations.
最初为碳氢化合物设计的分子连接性指数χ，已正式扩展到含杂原子的分子。杂原子的σ值经修改以考虑其连接氢原子的数量，即σiv = Zv - hi。这些值在沸点和摩尔折射度方面得到了成功验证。文中给出了氮、氧、氟、氯、溴和碘在各种键合情况下的σv值表。
