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Review | Regular issue | Vol 32, No. 10, 1991, pp.2023-2041
Published online, 1st January, 1970
DOI: 10.3987/REV-91-435
The Relationship between Bond Type, Bond Order and Bond Lengths. A Re-evalution of the Aromaticity of Some Heterocyclic Molecules

Vernon G. S. Box

*Department of Chemistry, City College of the City University of New York, Convent Avenue @ 138th Street, New York, NY 10031, USA.


Traditionally, we have described the type of a bond in terms of its location along a continuum from single to triple bond. A review of the bond lengths of a variety of molecules (from the X-ray crystallographic data), along with VESCF calculations on some isoelectronic analogues of enamines, and their nmr spectroscopic data, indicated that bonds can only occur in integral units and that no bond can be of an intermediate type. This conclusion leads to a redifinition of aromaticity which definitively reveals the possible aromaticity of heterocyclic molecules.