Authors: Sivani Baskaran | Akshay Podagatlapalli | Alessandro Sangion | Frank Wania
Source: Journal of Solution Chemistry (article, 2022-11-08)
Field: Chemistry — Organic Chemistry

Predicting the Temperature Dependence of the Octanol–Air Partition Ratio: A New Model for Estimating $$\Delta {U^{ \circ}_{\text{OA}}}$$ Abstract The octanol–air partition ratio ( K OA ) describes the partitioning of a chemical between air and octanol and is often used to approximate other partitioning phenomena in environmental chemistry (e.g., blood–air, atmospheric particulate matter–air, polyurethane foam-air). Such partitioning processes often occur at environmental temperatures other than 25 °C. Enthalpies $$\Delta {H^{ \circ}_{\text{OA}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mtext>OA</mml:mtext> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> or internal energies $$\Delta {U^{ \circ}_{\text{OA}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>U</mml:mi> <mml:mtext>OA</mml:mtext> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> of phase transfer are used to express the temperature dependence of the K OA . Existing poly-parameter linear free energy relationships (ppLFERs) for predicting $$\Delta {H^{ \circ}_{\text{OA}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mtext>OA</mml:mtext> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> were developed using a relatively small dataset. In this work we utilize a recently developed comprehensive K OA database to create and curate a $$\Delta {U^{ \circ}_{\text{OA}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>U</mml:mi> <mml:mtext>OA</mml:mtext> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> dataset containing 195 chemicals and use this dataset in the development of new predictive equations. Using the QSAR development platform QSARINS we evaluate the use of Abraham descriptors, other molecular descriptors, and the log 10 K OA at 25 °C as variables in different multilinear regression equations for $$\Delta {U^{ \circ}_{\text{OA}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>U</mml:mi> <mml:mtext>OA</mml:mtext> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> . The $$\Delta {U^{ \circ}_{\text{OA}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>U</mml:mi> <mml:mtext>OA</mml:mtext> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> of neutral organic chemicals can be reliably predicted using only the log 10 K OA (RMSE EXT = 6.86 kJ·mol −1 , $${\text{R}^{2} _{\text{adj}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mtext>R</mml:mtext> <mml:mtext>adj</mml:mtext> <mml:mn>2</mml:mn> </mml:msubsup> </mml:math> = 0.94), only the solute’s hydrogen acidity A and the logarithm of the hexadecane–air partition ratio L (RMSE EXT = 7.23 kJ·mol −1 , $${\text{R}^{2} _{\text{adj}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mtext>R</mml:mtext> <mml:mtext>adj</mml:mtext> <mml:mn>2</mml:mn> </mml:msubsup> </mml:math> = 0.93), or A and log 10 K OA (RMSE EXT = 6.76 kJ·mol −1 , $${\text{R}^{2} _{\text{adj}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mtext>R</mml:mtext> <mml:mtext>adj</mml:mtext> <mml:mn>2</mml:mn> </mml:msubsup> </mml:math> = 0.95). Algorithm ; Partition coefficient ; Chemistry ; Artificial intelligence ; Computer science ; Chromatography Chemical Thermodynamics and Molecular Structure ; Phase Equilibria and Thermodynamics ; Analytical Chemistry and Chromatography