ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 6, pp. 957!966. + Pleiades Publishing, Inc., 2006.
Original Russian Text + A.A. Kotomin, A.S. Kozlov, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 6, pp. 966 ! 977.
AND INDUSTRIAL ORGANIC CHEMISTRY
Calculation of Densities of Organic Compounds
from Contributions of Molecular Fragments
A. A. Kotomin and A. S. Kozlov
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received October 28, 2005
Abstract-A method for calculating the densities of organic compounds from the contributions of molec-
ular fragments was suggested. A correlation between the densities of solid and liquid substances at 20oC
Density is one of the main characteristics of sub-
stances. It is connected with the fundamental phys-
icochemical properties of substances and performance
of materials produced from them. Along with per-
forming a molecular design, it is necessary to forecast
the properties of organic compounds to be synthesized,
including density, which is required to design the pro-
duction process. Therefore, the development of the
most general and precise methods of density calcula-
tions is an topical problem, especially for high-energy-
capacity substances whose density largely determines
the efficiency, detonation power, sensitivity, and ten-
dency for passing from combustion to detonation.
Density is used in calculations of the detonation rate,
explosion energy, burning rate, detonation critical
diameter, and parameters of the impact of the explo-
sion on the environment .
All the known methods of density calculation can
be divided into three groups.
Theoretical methods. Molecular mechanics meth-
ods of Stine and Keddy allow calculation of the den-
sity of a substance from the basic physical character-
istics of the molecules, such as van der Waals atomic
radius, interatomic distances and angles, etc. In so
doing, principles of simulation of the molecular struc-
ture of solids and molecular crystal packing for various
steric configurations are used .
Empirical methods. The Smirnov, Tarver, Im-
mirizi, and Perini methods are additive and allow cal-
culation of the molar volume and substance density
using atomic or group contributions, and also cor-
rection and other factors calculated directly from
the measured densities of various types of organic
compounds [13, 14].
Semiempirical methods. Piacenza, Jacob, Grain-
dorge, Blaive, and Gallo methods include both phys-
ical characteristics of molecules and empirical coef-
The majority of methods estimating the density
through the atomic and group contributions operate
with a limited set of these and hence are insufficiently
general or have poor accuracy. For solid substances,
the theoretical, semiempirical, and empirical methods
give average relative calculation errors of 5.036.0,
3.033.5, and 2.033.0%, respectively. Therefore,
studies of correlations between the density and chem-
ical structure of the compounds and the development
of modern calculation methods are of interest.
We suggested a calculation method based on con-
tributions of molecular fragments. A complex system
of contributions to the molar volume was developed
for solid substances: aliphatic, alicyclic, aromatic, and
heteroaromatic compounds, including annelated and
skeleton compounds, and for combined structures
consisting of alicyclic and aromatic (heteroaromatic)
rings. The corrections for fragment interaction, struc-
ture type, and bonding between rings, allowing finer
consideration of the structural features, were found.
The contributions and corrections were derived from
the experimental densities and, correspondingly, from
the molar volumes of more than 6000 organic sub-
stances . The molar volume of each fragment
was calculated for 15325 compounds containing this