Temperature‐Dependent Prediction of the Liquid Entropy of Ionic Liquids

Modeling of the temperature‐dependent liquid entropy of ionic liquids (ILs) with great accuracy using COSMO‐RS is demonstrated. The minimum structures of eight IL ion pairs are investigated and the entropy, calculated from ion pairs, is found to differ on average only 2 % from the available experimental values (119 data points). For calculations with single ions, the average error amounts to 2.6 % and stronger‐coordinating ions tend to give higher deviations. Additionally, the first parameterization of the standard liquid entropy for ILs is presented in the context of traditional volume‐based thermodynamics (S_l⁰=1.585 kJ mol^?1 K^?1 nm^?3?r_m³+14.09 J mol^?1 K^?1), which sheds light on the statistical treatment of ionic interactions. The findings provide the first direct access to accurate predictions of liquid entropies of ILs, which are tedious and time‐consuming to measure.     

Structure-Toxicity Relationships for Aliphatic Compounds Encompassing a Variety of Mechanisms of Toxic Action to Vibrio fischeri

Abstract

QSARs based upon the logarithm of the octanol-water partition coefficient, logP, and energy of the lowest unoccupied molecular orbital, E_LUMO were developed to model the toxicity of aliphatic compounds to the marine bacterium Vibrio fischeri. Statistically robust, hydrophobic-dependent QSARs were found for chloroalcohols and haloacetonitriles. Modelling of the toxicity of the haloesters and the diones required the use of terms to describe both hydrophobicity and electrophilicity. The differences in intercepts, slopes, and fit of these models suggest different electrophilic mechanisms occur between classes, as well as within the diones and haloesters. In order to model globally the toxicity of aliphatic compounds to V. fischeri, all the data determined in this study were combined with those determined previously for alkanones, alkanals, and alkenals. A highly predictive two-parameter QSAR [pT₁₅ = 0.760(log P) ?0.625(E _LUMO) ?0.466; n = 63, s = 0.462, r ² = 0.846, F = 171, Pr > F = 0.0001] was developed for the combined data that models across classes and is independent of mechanisms of action. The toxicity of these compounds to V. fischeri compares well to the toxicity (50% population growth inhibition) to the ciliate Tetrahymena pyriformis (r ² = 0.850).     

Temperature Dependence of the Viscosity and Conductivity of Mildly Functionalized and Non‐Functionalized [Tf2N]− Ionic Liquids

A series of bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) with classical as well as mildly functionalized cations was prepared and their viscosities and conductivities were determined as a function of the temperature. Both were analyzed with respect to Arrhenius, Litovitz and Vogel–Fulcher–Tammann (VFT) behaviors, as well as in the context of their molecular volume (V_m). Their viscosity and conductivity are highly correlated with V_m/T or related expressions (R²≥0.94). With the knowledge of V_m of new cations, these correlations allow the temperature‐dependent prediction of the viscosity and conductivity of hitherto unknown, non‐ or mildly functionalized ILs with low error bars (0.05 and 0.04 log units, respectively). The influence of the cation structure and mild functionalization on the physical properties was studied with systematically altered cations, in which V_m remained similar. The T_o parameter obtained from the VFT fits was compared to the experimental glass temperature (T_g) and the T_g/T_o ratio for each IL was calculated using both experimental values and Angell’s relationship. With Walden plots we investigated the IL ionicity and interpreted it in relation to the cation effects on the physical IL properties. We checked the validity of these V_m/T relations by also including the recently published variable temperature viscosity and conductivity data of the [Al(OR^F)₄]^? ILs with R^F=C(H)(CF₃)₂ (error bars for the prediction: 0.09 and 0.10 log units, respectively).     

COMFA of the acute toxicity of phenylsulfonyl carboxylates to Vibrio fischeri

From the Comparative Molecular Field Analysis (CoMFA) method, the paper describes a three-dimentional quantitative structure–activity relationship (3D-QSAR) model for the acute toxicity log EC₅₀ (15min-EC₅₀ in μmoll^-l) of 56 phenylsulfonyl carboxylates on Vibrio fischeri. The achievement of a high leave-one-out (LOO) cross-validated correlation coefficient q² of 0.790 with four optimum components indicates the significance of the correlation of the steric and electrostatic fields with the biological activities. The key features in the CoMFA contour maps are critical to trace the important properties and gain insight into the toxic mechanism of the tested phenylsulfonyl carboxylates.