Thermodynamical and quantum-chemical characterization and chemometrical selection of representative congeners oftrans-chloroazoxybenzene

Abstract

Polychlorinated trans-azoxybenzenes (PCt-AOBs) consist a group of 399 theoretically possible congeners, which are toxicologically and environmentally relevant compounds. Some of PCt-AOBs have been identified as by-side impurity in technical grade 3,4-dichloroaniline (3,4-DCA), and also in derived of this chemical pesticides such as Diuron, Linuron or Propanil. In this study 31 quantum-chemical descriptors were in silico generated and used to characterize all 399 PCt-AOBs. Further, the basic thermodynamic and quantum-chemical property data matrix of PCt-AOBs made was interpreted with an aid of the Principal Component Analysis (PCA). The PCA of these data matrix created a three-dimensional model that explained 77.31% (63.79% + 8.87% + 4.65%) of the total variance. Polarizability, molecular weight, logarithm of the n-octanol/water partition coefficient, molecular refraction, valence molecular index, kappa index, molecular connectivity index, thermal capacity and entropy were the best positively correlated descriptors, which all are connected with molecular shape and size of the molecules. They all are explained by the first principal component (PC1), while energy of the highest occupied molecular orbital, Gibbs free energy in gas phase, standard heat of formation, the total particle energy and thermal energy were negatively correlated. The PC2 depended on polarizability vector Z and energy of the lowest unoccupied molecular orbital, while the PC3 was negatively impacted by the most positive partial charge on atoms. The congeners of trans-PCAOBs substituted with chlorine at positions 2' (ortho position) are non-planar. 119 Congeners of trans-chloroazoxybenzene (Ct-AOB) could be classified amongst stereoisomers (analogues) to highly toxic and environmentally persistent 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). Data obtained after PCA were further used to create Fractional Factorial Design of PCt-AOBs and eight congeners, i.e., 2',3'-DiCt-AOB (no. 11), 2,2',5-TrCt-AOB (no. 32), 3',4'-DiCt-AOB (no. 24), 2,4,5-TrCt-AOB (no. 58), 2,2',3,4',5,5'-HeCt-AOB (no. 271), 2,2',3',4',5,5',6'-HpCt-AOB (no. 360), 2,3,3',4,4',5',6-HpCt-AOB (no. 364) and 2,2',3,3',4',5',6'-HpCt-AOB (no. 337), which probably are the best describers of the whole group, could be assigned.

N-octanol-water partition coefficients (log KOW) of 399 congeners of polychlorinated azoxybenzenes (PCAOBs) determined by QSPR- and ANN-based approach

“…399 Congeners of PCAOBs have cis conformation and 399 have trans, and in the case of PCABs is 209 of cis and 209 of trans configuration. [6][7] The trans forms of PCAOBs and PCABs are more stable thermo chemically and they are considered as environmentally more relevant compared to the cis forms. [8] 3,3 ,4,4 -TeCAOB and 3,3 ,4,4 -TeCAB, because of high toxicity are the best known compounds of PCAOBs and PCABs.…”

Use of quantitative-structure property relationship (QSPR) and artificial neural network (ANN) based approaches for estimating the octanol-water partition coefficients of the 209 chlorinatedtrans-azobenzene congeners

“…Amongs the Ct-ABs are compounds having a planar-like configuration and these Ct-ABs can be considered as analogues to highly toxic 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and having similar toxic and persistent nature. [5][6][11][12] There is a limited number of experimentally derived toxicity data existing on PCt-ABs, and most relates to 3,3 ,4,4 -TeCt-azobenzene (3,3 ,4,4 -TeCt-AB) toxicity. [5,11,[13][14] Also highly limited is the amount of data on physical and chemical properties of PCABs.…”

“…[1][2][3][4][5][6] The source of PCt-ABs in these contaminated herbicides is 3,4-dichloroaniline (3,4-DCA) that is a substrate used for synthesis of the herbicidal active agent. [1] Use of herbicides contaminated with PCt-ABs leads to pollution of the the soils and crops with these toxic compounds.…”

Multivariate analysis of toxicological and environmental properties of soil nematicides

“…PCA analyses have been extensively used to relate sets of variables and allocate observations on multidimensional spaces determined by independent axes. They make it possible, for example, to study the toxic effects of pesticides on animals,19 characterizing the chemical properties of pesticide families,20 or relating pesticide structural properties and toxicity 21. Although active substances included in this comparison present different structures and modes of action, and are used at different moments of the cropping cycle, they all may be used to control plant‐parasitic nematodes, and their toxicological and environmental attributes have been calculated by standardized methods.…”