Abstract
There is demand for safer and bio-based solvents, brought on by legislation and sustainability objectives. The prediction of physical properties is highly desirable to help design new molecules. Here we present an in silico approach to obtain calculated Kamlet–Abboud–Taft solvatochromic parameters using virtual experiments. The tautomerisation equilibrium of methyl acetoacetate and dimedone was calculated in different solvents with COSMO-RS theory and converted into estimates of solvent dipolarity and hydrogen bond accepting ability, respectively. Hydrogen bond donating ability was calculated as a function of the electron deficient surface area on protic solvents. These polarity descriptors correlate with rate constants and equilibria, and so ability of calculated Kamlet–Abboud–Taft solvatochromic parameters to recreate experimental free energy relationships was tested with sixteen case studies taken from the literature. The accuracy of the calculated parameters was also satisfactory for solvent selection, as demonstrated with a 1,4-addition reaction and a multicomponent heterocycle synthesis.
Highlights
The rate of a reaction [1,2], and product selectivity [3,4,5], can be favourably tuned by the astute application of the most appropriate solvent
Simple and computationally fast group contribution methods are available to predict the physical properties of solvents. None of these properties reliably correlate with reaction kinetics, thermodynamics, or product yields, which determines the suitability of a solvent
Experimental data for nine solvents were used to validate the accuracy of the calculated equilibrium data for nine solvents to relationships validate the accuracy of the calculated constantsExperimental for the tautomerisation of 1 andwere
Summary
The rate of a reaction [1,2], and product selectivity [3,4,5], can be favourably tuned by the astute application of the most appropriate solvent. Following decades of research into catalyst optimisation [8,9], solvent selection and even the design of bespoke solvents for greater reaction performance has only recently reached prominence [10,11,12,13]. Simple and computationally fast group contribution methods are available to predict the physical properties of solvents (boiling point, density, viscosity, etc.). None of these properties reliably correlate with reaction kinetics, thermodynamics, or product yields, which determines the suitability of a solvent (assuming it is safe to use)
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