scholarly journals Predicting Partition Coefficients of Short-Chain Chlorinated Paraffin Congeners by COSMO-RS-Trained Fragment Contribution Models

2020 ◽  
Vol 54 (23) ◽  
pp. 15162-15169
Author(s):  
Satoshi Endo ◽  
Jort Hammer
2020 ◽  
Author(s):  
Satoshi Endo ◽  
Jort Hammer

Chlorinated paraffins (CPs) are highly complex mixtures of polychlorinated <i>n</i>-alkanes with differing chain lengths and chlorination patterns. Knowledge on physicochemical properties of individual congeners is limited but needed to understand their environmental fate and potential risks. This work uses a sophisticated but time-demanding quantum chemically based method COSMO-RS and a fast-running fragment contribution approach to enable prediction of partition coefficients for a large number of short-chain chlorinated paraffin (SCCP) congeners. Fragment contribution models (FCMs) were developed using molecular fragments with a length of up to C<sub>4</sub> in CP molecules as explanatory variables and COSMO-RS-calculated partition coefficients as training data. The resulting FCMs can quickly provide COSMO-RS predictions for octanol–water (<i>K</i><sub>ow</sub>), air–water (<i>K</i><sub>aw</sub>), and octanol–air (<i>K</i><sub>oa</sub>) partition coefficients of SCCP congeners with an accuracy of 0.1–0.3 log units root mean squared errors. The FCM predictions for <i>K</i><sub>ow</sub> agree with experimental values for individual constitutional isomers within 1 log unit. The distribution of partition coefficients for each SCCP congener group was computed, which successfully reproduced experimental log <i>K</i><sub>ow</sub> ranges of industrial CP mixtures. As an application of the developed FCMs, the predicted <i>K</i><sub>aw</sub> and <i>K</i><sub>oa</sub> were plotted to evaluate the bioaccumulation potential of each SCCP congener group.<br>


2020 ◽  
Author(s):  
Satoshi Endo ◽  
Jort Hammer

Chlorinated paraffins (CPs) are highly complex mixtures of polychlorinated <i>n</i>-alkanes with differing chain lengths and chlorination patterns. Knowledge on physicochemical properties of individual congeners is limited but needed to understand their environmental fate and potential risks. This work combines a sophisticated but time-demanding quantum chemically based method COSMO-RS and a fast-running fragment contribution approach to establish models to predict partition coefficients of a large number of short-chain chlorinated paraffin (SCCP) congeners. Molecular fragments of a length of up to C<sub>4</sub> in CP molecules were counted and used as explanatory variables to develop linear regression models for predicting COSMO-RS-calculated values. The resulting models can quickly provide COSMO-RS predictions for octanol–water (<i>K</i><sub>ow</sub>), air–water (<i>K</i><sub>aw</sub>), and octanol–air (<i>K</i><sub>oa</sub>) partition coefficients of SCCP congeners with an accuracy of 0.1–0.3 log units root mean squared errors (RMSE). The model predictions for <i>K</i><sub>ow</sub> agree with experimental values for individual constitutional isomers within 1 log unit. The ranges of partition coefficients for each SCCP congener group were computed, which successfully reproduced experimental log <i>K</i><sub>ow</sub> ranges of industrial CP mixtures. As an application of the developed approach, the predicted <i>K</i><sub>aw</sub> and <i>K</i><sub>oa</sub> were plotted to evaluate the bioaccumulation potential of each SCCP congener group.


2020 ◽  
Author(s):  
Satoshi Endo ◽  
Jort Hammer

Chlorinated paraffins (CPs) are highly complex mixtures of polychlorinated <i>n</i>-alkanes with differing chain lengths and chlorination patterns. Knowledge on physicochemical properties of individual congeners is limited but needed to understand their environmental fate and potential risks. This work combines a sophisticated but time-demanding quantum chemically based method COSMO-RS and a fast-running fragment contribution approach to establish models to predict partition coefficients of a large number of short-chain chlorinated paraffin (SCCP) congeners. Molecular fragments of a length of up to C<sub>4</sub> in CP molecules were counted and used as explanatory variables to develop linear regression models for predicting COSMO-RS-calculated values. The resulting models can quickly provide COSMO-RS predictions for octanol–water (<i>K</i><sub>ow</sub>), air–water (<i>K</i><sub>aw</sub>), and octanol–air (<i>K</i><sub>oa</sub>) partition coefficients of SCCP congeners with an accuracy of 0.1–0.3 log units root mean squared errors (RMSE). The model predictions for <i>K</i><sub>ow</sub> agree with experimental values for individual constitutional isomers within 1 log unit. The ranges of partition coefficients for each SCCP congener group were computed, which successfully reproduced experimental log <i>K</i><sub>ow</sub> ranges of industrial CP mixtures. As an application of the developed approach, the predicted <i>K</i><sub>aw</sub> and <i>K</i><sub>oa</sub> were plotted to evaluate the bioaccumulation potential of each SCCP congener group.


2020 ◽  
Author(s):  
Satoshi Endo ◽  
Jort Hammer

Chlorinated paraffins (CPs) are highly complex mixtures of polychlorinated <i>n</i>-alkanes with differing chain lengths and chlorination patterns. Knowledge on physicochemical properties of individual congeners is limited but needed to understand their environmental fate and potential risks. This work uses a sophisticated but time-demanding quantum chemically based method COSMO-RS and a fast-running fragment contribution approach to enable prediction of partition coefficients for a large number of short-chain chlorinated paraffin (SCCP) congeners. Fragment contribution models (FCMs) were developed using molecular fragments with a length of up to C<sub>4</sub> in CP molecules as explanatory variables and COSMO-RS-calculated partition coefficients as training data. The resulting FCMs can quickly provide COSMO-RS predictions for octanol–water (<i>K</i><sub>ow</sub>), air–water (<i>K</i><sub>aw</sub>), and octanol–air (<i>K</i><sub>oa</sub>) partition coefficients of SCCP congeners with an accuracy of 0.1–0.3 log units root mean squared errors. The FCM predictions for <i>K</i><sub>ow</sub> agree with experimental values for individual constitutional isomers within 1 log unit. The distribution of partition coefficients for each SCCP congener group was computed, which successfully reproduced experimental log <i>K</i><sub>ow</sub> ranges of industrial CP mixtures. As an application of the developed FCMs, the predicted <i>K</i><sub>aw</sub> and <i>K</i><sub>oa</sub> were plotted to evaluate the bioaccumulation potential of each SCCP congener group.<br>


2021 ◽  
Author(s):  
Satoshi Endo

COSMO-RS-trained fragment contribution models (FCMs) to predict partition properties of chlorinated paraffin (CP) congeners were refined and extended. The improvement includes (i) the use of an improved conformer generation method for COSMO-RS, (ii) extension of training and validation sets for FCMs up to C<sub>20</sub> congeners covering short-chain (SCCPs), medium-chain (MCCPs) and long-chain CPs (LCCPs), and (iii) more realistic simulation of industrial CP mixture compositions by using a stochastic algorithm. Extension of the training set markedly improved the accuracy of model predictions for MCCPs and LCCPs, as compared to the previous study. The predicted values of the log octanol/water partition coefficients (<i>K</i><sub>ow</sub>) for CP mixtures agreed well with experimentally determined values from the literature. Using the established FCMs, this study provided a set of quantum chemically based predictions for 193 congener groups (C<sub>10–20</sub>, Cl<sub>0–21</sub>) regarding <i>K</i><sub>ow</sub>, air/water (<i>K</i><sub>aw</sub>), and octanol/air (<i>K</i><sub>oa</sub>) partition coefficients, subcooled liquid vapor pressure (VP) and aqueous solubility (<i>S</i><sub>w</sub>) in a temperature range of 5–45 °C as well as the respective enthalpy and internal energy changes.<br><br>This is a preprint version and has not yet been peer reviewed.


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