Multivariate QSARs to model the hydroxyl radical rate constant for halogenated aliphatic hydrocarbons

Abstract

SUMMARYMultivariate quantitative structure-activity relationships (QSARs) are applied to model the atmospheric persistence of halogenated aliphatic hydrocarbons. The objective is to forecast the rate of reaction between the haloalkanes and the hydroxyl radical in the gas phase. The QSARs are developed in the light of a recently proposed strategy for risk assessment of environmental chemicals, based on multivariate data analysis and statistical experimental design. The QSARs are calibrated using a training set consisting of ten chemicals and different sets of descriptors, namely empirical and qualitative indicator variables and quantum-chemical descriptors. The predictabilities of the QSARs are investigated by making predictions for 13 additional compounds for which experimental observations exist. Finally, the best obtained set of descriptors is used as a basis for making predictions for 35 non-tested haloalkanes.

“Anticonnectivity”: A Challenge for Structure−Property−Activity Studies

“…[36][37][38] To reduce the analysis time and costs of such measurements, it would be useful to develop a theoretical prediction model to estimate these values. Several QSPR models based on the fragment contribution technique, 39 the bond dissociation energy, 40,41 the ionization potentials, 42 the molecular orbital calculations, [43][44][45][46] and various molecular descriptors [47][48][49][50][51] are already available. The comprehensive overviews of these methods together with their partial evaluations were recently published.…”

“…Up to now, experimental reaction rate constants are available only for around 500 VOCs. − To reduce the analysis time and costs of such measurements, it would be useful to develop a theoretical prediction model to estimate these values. Several QSPR models based on the fragment contribution technique, the bond dissociation energy, , the ionization potentials, the molecular orbital calculations, − and various molecular descriptors − are already available. The comprehensive overviews of these methods together with their partial evaluations were recently published. , Although the present modeling techniques offer moderate prediction capabilities, the development of a simple prediction model, which enables a good structural interpretation, continues to be of interest and would be beneficial.…”

Correlations between experimental and theoretical adiabatic ionization energies for organic compounds and rate constants for atmospheric reactions with hydroxyl radicals

“…In addition to experimental approaches, theoretical methods for predicting the rate constants for reaction of organic compounds with the hydroxyl radical (k OH ) have been the focus of a number of studies. In general, these predictive investigations have taken one of three general tactics [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]: (1) rigorous and time-intensive medium-through high-level computational studies (e.g., density functional theory, composite methods) on all possible mechanistic pathways for the reaction of a particular compound with the hydroxyl radical (i.e., addition to unsaturated groups, hydrogen abstractions, etc. ); (2) regression based quantitative structure-activity relationship (QSAR) models employing a range of two-and threedimensional molecular descriptors; and (3) univariate correlations with physicochemical properties (e.g., ionization energies [IEs], bond dissociation enthalpies [BDEs]).…”

Using Variable and Fixed Topological Indices for the Prediction of Reaction Rate Constants of Volatile Unsaturated Hydrocarbons with OH Radicals

“…Recently, several quantitative structure property relationship (QSPR) prediction models were developed to predict reaction rate constants for the reaction of OH radicals with different organic species. These models estimated reaction rate constants based on empirical fragment contribution technique [4][5][6], bond dissociation energy [7][8][9], NMR chemical shift data [10], ionization potentials [11][12][13], molecular orbital calculations [14][15][16][17][18][19][20][21] and various structural descriptors [22][23][24][25][26][27]. A comprehensive overview [28] of these method and their partial evaluations were recently published [29].…”