Vapor pressures of carboxylic acid esters including pyrethroids: measurement and estimation from molecular structure Original Research Article

We developed an accurate noncorrelative way of estimating vapor pressures of carboxylic acid esters, including pyrethroid insecticides, in the range 10−6–100 Pa, by altering the modified Watson method. The new thermodynamic method requires no data other than the chemical structure of the compound. It consists of the modified Watson method with the empirical parameter adjusting the temperature dependency of heat of vaporization changed to a function of boiling point. A comparison of this method with two correlative methods, using molecular connectivity indexes and molecular descriptors for the 20 esters of the training set, showed a similar level of accuracy for each method, but only the new method could predict vapor pressure within one log unit for esters not used in the statistical analysis.