Prediction of the auto-ignition temperature of binary liquid mixtures based on the quantitative structure–property relationship approach

Journal of Thermal Analysis and Calorimetry - The auto-ignition temperature (AIT) is one of the most important parameters in flammability risk assessment and management in the chemical process....     

Prediction of lower flammability limits of blended gases based on quantitative structure–property relationship

Journal of Thermal Analysis and Calorimetry - The main goal of this research was to improve a carbonate-type foaming agent for the production of Al foams. Various systematic treatments, i.e....     

A quantitative structure–mobility relationship of organic acids using solvation parameters

A quantitative structure–mobility relationship (QSMR) is proposed to estimate the electrophoretic mobility of diverse sets of analyses in capillary zone electrophoresis using Abraham solvation parameters of analyses, such as the excess molar refraction, polarizability, hydrogen bond acidity, basicity, and molar volume. QSMR was developed for prediction the electrophoretic mobility of 231 organic acids using the solvation parameters calculated by Abraham. Multiple linear regression (MLR) as a linear model and artificial neural network (ANN) methods were used to evaluate the nonlinear behavior of the involved parameters. The prediction results are obtained by nonlinear model, ANN, seem to be superior over MLR and were in good agreement with experimental data. In the proposed ANN–QSMR model, the overall mean percentage deviation values were 5.6, 5.4, and 5.3% and the coefficients of determinations (R²) were 0.84, 0.84, and 0.84 for training, test, and verification set, respectively. To investigate the robustness of the model, cross-validation methods have been established, i.e., leave-one-out and leave-N-out (N?=?5 and 10) and model is showed good predictive ability against data variation in cross-validation process. This model is not only able to accurately predict the migration order of a diverse set of organic acids but also model finds that solvation parameters are responsible in separation mechanism.     

New approach to unravel the structure–property relationship of methylcellulose

In the present paper we suggest a new concept to overcome some of the so far unsolved problems of the structure–property relationship of methylcellulose, the most important nonionic cellulose ether industrially produced in large scale. Not only from the viewpoint of scientific understanding, but also from that of the peculiar and application-determining behavior, the aggregation in aqueous solution and phase separation on heating are the most important questions. As a part of the concept, we had prepared amphiphilic block co-oligomers of tri-O-methylated and unmodified cello-oligosaccharides as structural models of typical sequences in methylcellulose chains. Now static and dynamic light scattering measurements and transmission electron microscopy (TEM) were carried out using solutions of the oligomers in water. Ellipsoidal particles with dimensions of about 50 nm for the semi-major axis and of circa 25 nm for the semi-minor one could be detected. These findings agree with the radii of gyration and the hydrodynamic radii, determined by static and dynamic light scattering. The data preliminary obtained demonstrate the strong aggregation tendency of block-like methylated cello-oligosaccharides.     

Thermal hazard assessment and ranking for organic peroxides using quantitative structure–property relationship approaches

Journal of Thermal Analysis and Calorimetry - Chemical reactivity hazards of organic peroxides are major concerns of the chemical industry due to many serious incidents every year. Thermal hazard...     

Quantum chemical investigations on the structure–property relationship of aminopolynitrotriazoles

Density functional theory (DFT) has been employed to study the geometric and electronic structures, band gap, thermodynamic properties, density, and performance properties of a series of polynitrotriazoles at the B3LYP/aug-cc-pVDZ level. The detonation performances were evaluated by the Kamlet–Jacobs semi-empirical equations based on the calculated densities and heats of reaction. It has been found that the model compounds with the predicted densities of 1.8 g/cm³, detonation velocities of 8.8 km/s, and detonation pressures of 35 GPa may be novel potential candidates of high energy density materials. The discrepancies in the performance properties, stabilities or sensitivities among isomers are caused by the relative position of NH₂ and NO₂ groups.     

How not to develop a quantitative structure–activity or structure–property relationship (QSAR/QSPR)

Although thousands of quantitative structure–activity and structure–property relationships (QSARs/QSPRs) have been published, as well as numerous papers on the correct procedures for QSAR/QSPR analysis, many analyses are still carried out incorrectly, or in a less than satisfactory manner. We have identified 21 types of error that continue to be perpetrated in the QSAR/QSPR literature, and each of these is discussed, with examples (including some of our own). Where appropriate, we make recommendations for avoiding errors and for improving and enhancing QSAR/QSPR analyses.     

A DFT study on the structure–property relationship of amino-, nitro- and nitrosotetrazoles, and their N-oxides: new high energy density molecules

We explore herein the structure, stability, heat of explosion, density, and the performance properties of amino, nitro, and nitroso substituted tetrazoles and their N-oxides using the density functional theory calculations at the B3LYP/aug-cc-pVDZ level. N-Nitro compounds have lower densities compared with those of C-nitrotetrazoles. Kamlet-Jacob semi-empirical equations were used to calculate the performance properties of designed compounds. The higher performance of tetrazole-N-oxides is due to their higher densities (2.110–2.287 g/cm³). Heat of explosion, stability, density and performance properties are related to the number and relative positions of NO₂, NH₂, and NO groups of the tetrazole ring. The designed molecules satisfy the criteria of high energy materials.     

A new P-heterocyclic type of phosphonium–iodonium ylides based on dibenzophosphole

A novel mixed phosphonium–iodonium ylide was synthesized by alkylation of 5-phenyl-5H-dibenzophosphole with phenacyl bromide followed by deprotonation and oxidation of the resulting phosphonium ylide with (diacetoxyiodo)- benzene. The influence of the cyclic nature of the phosphonium moiety on the dynamic E/Z isomerism in the mixed ylide is discussed.     

Visual exploration of structure–activity relationship using maximum common framework

To help tracking all molecules made in a typical medicinal chemistry project, we have developed an algorithm to generate a maximum common framework (MCF) hierarchy and an interactive tool for its visualization and analysis. By identifying all unique frameworks for a set of molecules and all molecules containing each framework, we were able to simplify the MCF hierarchy build up steps and, as a result, speed up the entire process significantly. By allowing compounds to be assigned to multiple MCFs, users can easily remove bad branching nodes and concentrate on interesting ones. MCF hierarchies provide an effective and intuitive visualization for tracking medicinal chemistry lead optimization projects. We will provide examples to illustrate its usefulness.