STANDARD CHEMICAL THERMODYNAMIC PROPERTIES OF MULTICHLORO ALKANES ANDALKENES - A MODIFIED GROUP ADDITIVITY SCHEME

Chlorinated hydrocarbon groups plus non-next-nearest-neighbor interact ion terms, which combine with the Benson group additivity method for e stimation of thermodynamic properties (Delta H-f(o), S-o and C-p(T)(30 0-1500 K) on multichloro alkanes and alkenes, are developed. New chlor ocarbon alkane and alkene Benson-type group values are derived from mo lecule systems where no chlorines are on the carbon adjacent to the ca rbon atom bonded to chlorine(s). A set of interaction terms for Delta H-f(o), S-o, and C-p(T)(300-1500 K) is derived to account for non-next -nearest-neighbor chlorine-chlorine interactions. These are derived fr om the experimental thermodynamic property data on 28 chlorinated hydr ocarbons species and current hydrocarbon groups. Thermodynamic propert ies for representative multichloro alkanes and alkenes determined usin g this modified group additivity scheme are compared with literature d ata and show good agreement (Delta H-o,298(f) = +/-0.29 kcal/ mol, S-2 98(o) = +/-0.68 cal/mol.K, and C-p(T) = +/-0.23 cal/mol.K). The use of a limited number of interaction groups provides improved accuracy in calculation of thermodynamic properties for multichloro alkanes and al kenes when chlorines are on adjacent carbon atoms. We develop three mu ltichloro Benson groups plus five interaction groups for chloroalkanes , and two groups plus five interaction groups for chloroalkenes. This non-next-nearest-neighbor interaction group approach accounts for 13.6 kcal/mol in standard enthalpy for hexachloroethane and 2.7 cal/mol.K in standard entropy for tetrachloroethylene. The multichloro groups co mbined with the interaction groups allow estimation of thermodynamic p roperties (Delta H-f(o), S-o, and C-p(T)-(300-1500 K)) on larger multi chlorocarbon species, where no thermodynamic property data or accurate estimation techniques are available.