Molecular structure and molar volume of organic compounds and complexes with special reference to coal

Determination of molar volume of coal, more particularly of its hydrocarbon analogue, is the key parameter of a revised densimetric approach for precise estimates of aromaticity (f(a)). This has been rendered much simpler by two recent correlations, one for He-density (d(4)(20)), and the other for molar volume of the coal itself, directly from its elemental composition, thus eliminating the need for density determination and the elaborate volume corrections for hetero-atom groups (O, N and S). The accuracy of the correlations is further substantiated in the present work vis-a-vis the system of atom and group contributions presented by D.W. van Krevelen for molar volume computations. Studies of some coal models have not only borne out the claims, but have also led to the development of a modified system, more accurate and comprehensive in its applicability to organic compounds and complexes. The scope and limitations of the new system are also discussed in this article. (C) 1999 Elsevier Science Ltd. All rights reserved.