SIMPOL.1: A simple group contribution method for predicting vapor pressures and enthalpies of vaporization of multifunctional organic compounds

J. F. Pankow (1) , W. E. Asher (1, 2)

1 Department of Environmental and Biomolecular Systems
2 Air-Sea Interaction and Remote Sensing Department

The SIMPOL.1 group contribution method is developed for predicting the liquid vapor pressure p_L^o (atm) and enthalpy of vaporization ?H_vap (kJ mol^-1) of organic compounds as functions of temperature (T). For each compound i, the method assumes log₁₀p_L,i^o(T)=?_k?_k,ib_k(T) where ?_k,i is the number of groups of type k, and b_k(T) is the contribution to log₁₀ p_L,i^o(T) by each group of type k. A zeroeth group is included that uses b₀(T) with ?_0,i=1 for all i. A total of 30 structural groups are considered: molecular carbon, alkyl hydroxyl, aromatic hydroxyl, alkyl ether, alkyl ring ether, aromatic ether, aldehyde, ketone, carboxylic acid, ester, nitrate, nitro, alkyl amine (primary, secondary, and tertiary), aromatic amine, amide (primary, secondary, and tertiary), peroxide, hydroperoxide, peroxy acid, C=C, carbonylperoxynitrate, nitro-phenol, nitro-ester, aromatic rings, non-aromatic rings, C=C?C=O in a non-aromatic ring, and carbon on the acid-side of an amide. The T dependence in each of the b_k(T) is assumed to follow b(T)=B₁/T+B₂+B₃T+B₄lnT. Values of the B coefficients are fit using an initial basis set of 272 compounds for which experimentally based functions p_L,i^o=f_i(T) are available. The range of vapor pressure considered spans fourteen orders of magnitude. The ability of the initially fitted B coefficients to predict p_L^o values is examined using a test set of 161 compounds and a T range that is as wide as 273.15 to 393.15 K for some compounds. ?_FIT is defined as the average over all points of the absolute value of the difference between experimental and predicted values of log₁₀p_L,i^o(T). After consideration of ?_FIT for the test set, the initial basis set and test set compounds are combined, and the B coefficients re-optimized. For all compounds and temperatures, ?_FIT=0.34: on average, p_L,i^o(T) values are predicted to within a factor of 2. Because d(log₁₀p_L,i^o(T))/d(1/T) is related to the enthalpy of vaporization ?H_vap,i, the fitted B provide predictions of ?H_vap,i based on structure.

Domaines: Océan, Atmosphère

J. F. Pankow, W. E. Asher. SIMPOL.1: A simple group contribution method for predicting vapor pressures and enthalpies of vaporization of multifunctional organic compounds. Atmospheric Chemistry and Physics Discussions, 2007, 7 (4), pp.11839-11894. ⟨hal-00303048⟩