The simplest approach for the hand calculation of pseudo-first order rate constants for abiotic reduction of organic compounds

Abstract

Abstract A new method is introduced to predict pseudo-first order rate constants (kobs) for abiotic reduction of organic compounds with diverse reducible functional groups, including aliphatic nitro-compounds (ANCs), nitroaromatic compounds (NACs), aromatic N-oxides (ANOs), polyhalogenated alkanes (PHAs), isoxazoles (ISXs), sulfoxides and sulfones (SOs), and others. The largest experimental data of -logkobs for 59 organic compounds are used to derive and test the new model. In comparison to available quantitative structure-activity relationship (QSAR) methods where need computer codes, complex descriptors, and expert users, the novel method requires experimental conditions and structural parameters of the desired organic compounds. The calculated outputs of the new method are compared with the results of one of the best QSARs methods, which requires energy of the lowest-unoccupied molecular orbital. The values of statistical factors comprising average absolute deviation (AAD), mean error (ME), absolute maximum deviation (ADmax), average absolute relative deviation (AARD%), and R-squared (R2) of the estimated outputs for 54/5 training/test data sets of the new method are 0.663/1.311, -0.056/-0.165, 1.788/1.215, 19.10/74.07, and 0.796/0.958, respectively. Meanwhile, AAD, ME, ADmax, AAD%, and R2 for comparative QSAR method are 0.731/2.301, 0.601/1.126, 3.795/3.732, 641/821, and 0.003/0.447, respectively. Thus, the new model provides the simplest approach for the hand calculation of -logkobs with great goodness-of-fit, reliability, precision, and accuracy.