Energy Of The Lowest Unoccupied Molecular Orbital Research Articles

Synthesis, characterization and theoretical determination of corrosion inhibitor activities of some new 4,5-dihydro-1H-1,2,4-Triazol-5-one derivatives

Nine novel {bis-4-[(3-alkyl-5-oxo-1H-1,2,4-triazol-4(5H)-yl)-iminomethyl]-phenyl} [1,1′-biphenyl]-4,4′-disulfonates were synthesized and their structures were determined with spectral methods. Corrosion inhibitor activities of the title compounds were investigated using quantum mechanical methods. The parameters such as the Energy of the Highest Occupied Molecular Orbital (EHOMO), Energy of the Lowest Unoccupied Molecular Orbital (ELUMO), energy gap (ΔE = ELUMO - EHOMO) and dipole moment (μ) which are related to the corrosion effectivity of the organic compounds whose the molecular geometry and electronic properties are especially studied, were determined by using the density function theory method. Using these calculation results, properties such as hardness (ɳ), softness (σ), electronegativity (χ) values were calculated. Also quantum chemical parameters such as the fraction of transferred electrons (ΔN) between the iron surface and the 4,5-dihydro-1H-1,2,4-triazole-5-one derivative compounds were calculated. It has been discussed that which parameters have a good linear relationship with inhibition efficiency.The results of the calculations show that there is a close relationship between the activity of organic-based corrosion inhibitors showing good corrosion inhibitor activity and the calculated quantum chemical parameters of the process. Thus, corrosion inhibitor activity can be predicted without conducting an experimental study.

QSAR modelling for predicting the toxic effects of traditional and derived biomass solvents on a Danio rerio biomodel

The increasing interest in the development of ecofriendly solvents has led to the synthesis of benign alternative chemicals with minimized environmental impacts. These kinds of chemicals are known as Green solvents. In this work, we selected three families of solvents (furfural, lactate and levulinate families) derived from biomass that are structurally related. Most of the previous ecotoxicological studies of these solvents have focused on invertebrate models such as bacteria, algae and crustaceans. To complete this information, in this work, the acute toxicity of these solvents was studied in Danio rerio (D. rerio). Sublethal and lethal effects were also observed, and the LC50 was obtained. The LC50 values ranged from 13.21 to 12073 mg L−1, with furfural being the most toxic compound and tetrahydrofurfuryl alcohol the least toxic. Furthermore, the results indicated that a frequent sublethal effect was heart oedema or malformation, even in some cases at concentrations lower than the LC50.A QSAR analysis was also performed to model the toxicological effect towards D. rerio for the studied solvents obtained from biomass and traditional solvents. A total of 15 molecular descriptors of the solvents were obtained using Gaussian 03 software. Finally, we also used the physicochemical property Log P, calculated from ACD/LogP, for QSAR modelling. Multivariable regression analysis showed that the minimum set of independent variables that leads to the best regression is Log P, the energy of the lowest unoccupied molecular orbital (ELUMO) and the heat capacity (CV). The proposed model was validated using several internal and external methods.

Computational Evaluation of Corrosion Inhibition of Four Quinoline Derivatives on Carbon Steel in Aqueous Phase

Molecular Dynamics (MD) simulation and Density Functional Theory (DFT) methods have been used to evaluate the efficiency of four quinoline derivatives on corrosion inhibition in the aqueous phase. Some quantum chemical parameters such as hardness (η), electrophilicity (w), polarizability (a), energy of the highest occupied molecular orbital (EHOMO), energy of the lowest unoccupied molecular orbital (ELUMO), electronegativity (c), total amount of electronic charge transferred (ΔN), Total Negative Charges (TNC) on the whole of the molecule, Molecular Volume (MV), surface area and Fukui index were calculated. Molecular dynamics simulation showed a view of the dynamic evolution of the interaction energy between surface of metal and inhibitors. Results of two methods showed QUIN4 inhibitor has higher negative interactions and efficiency as compared to the other inhibitors, which was consistent with the experimental report.

Quantitative structure-activity relationship models for predicting reaction rate constants of organic contaminants with hydrated electrons and their mechanistic pathways

The hydrated electron (eaq−)-based reduction processes are promising for removing organic pollutants in water engineering systems. The reductive kinetics, especially the second order rate constants (keaq−) of eaq− with organic compounds, is important for evaluating and modeling the advanced reduction processes. In this study, the keaq−values for aliphatic compounds and phenyl-based compounds are, for the first time, modeled by the quantitative structure-activity relationship (QSAR) method. The structural features governing the reactivity of two classes of organic compounds toward eaq− were revealed, and the energy of the lowest unoccupied molecular orbital (ELUMO), one-electron reduction potential (ERED) and polarizability (α) were found to be the important molecular parameters in both two models. The built QSAR models provide robust predictive tools for estimating the removal of emerging pollutants using eaq− during wastewater treatment processes. Additionally, quantum chemical calculations were employed to probe into the mechanism and feasibility of the single electron transfer (SET) pathway in the eaq−-based reduction process. The thermodynamic investigation suggests that the compounds with electron-withdrawing groups tend to possess higher keaq− and lower Gibbs free energy (ΔGSET) and Gibbs free energies of activation (∆‡GSET∘) than the ones with electron-donating groups, indicating the SET process occurs more readily. It is also found that the refractory halogenated compounds can achieve dehalogenation via the SET pathway.

Toxicity of some prevalent organic chemicals to tadpoles and comparison with toxicity to fish based on mode of toxic action

Although mode of action (MOA) plays a key role in the understanding of the toxic mechanism of chemicals, the MOAs of class-based compounds to tadpoles have not been investigated. To explore the MOAs, acute toxicity (expressed as log 1/LC50) to Rana chensinensis tadpoles were determined and molecular descriptors were calculated. Quantitative structure-activity relationship (QSAR) showed that toxicity to tadpoles is closely related to the chemical octanol/water partition coefficient (log KOW), energy of the lowest unoccupied molecular orbital (ELUMO), and number of hydrogen bond donors and acceptors (NHDA), representing the bio-uptake potential in tadpoles, the electrophilicity and hydrogen bonding capacity with target site(s), respectively. Comparison of the toxicity values between tadpoles and fish revealed that there were no significant differences for the overlapping compounds (average residual = 0.29 between tadpole and fish toxicity) with P values of interspecies correlation substantially less than 0.001. Classification of MOAs for the class-based compounds based on the excess toxicity calculated from toxicity ratio suggested that baseline, less inert compounds and some reactive or specifically-acting compounds share same MOAs between tadpoles and fish. Fish and tadpoles can serve as surrogates for each other in the safety evaluation of organic pollutants.

Corrosion Inhibition of Copper in 2M Nitric Acid Solution by 2-(Thiobenzyl)-5-Nitro-1H-Benzimidazole

Pickling with nitric acid is commonly practiced in industry for finishing metal surfaces. The use of inhibitors during the pickling operation is of very recent origin. The TBNBI inhibition effect on copper corrosion in 2M nitric acid solution was investigated by weight loss method in relation to the temperature (25 to 40°C) and inhibitor concentration range 10-4 to 5.10-3 M. The results show that TBNBI is a good inhibitor for copper and the inhibition efficiency increases with concentration of TBNBI but decreases with increase in temperature. The adsorption parameters (ΔGa0ds ,ΔHa0ds ,ΔSa0ds ) and the activation ones * * a a a (E ,ΔH ,ΔS ) for the corrosion process in inhibited and uninhibited nitric acid solution were also calculated using Arrhenius equations. It can be concluded that the adsorption of the compound is spontaneous and found to occur through both physisorption and chemisorption processes. The adsorbed film on copper surface was characterized using optic microscopy and Raman spectroscopy. The surface analysis confirmed the inhibition action of TBNBI. Quantum chemical calculations using Gaussian 09 at B3LYP level with 6-31G (d,p) basis set lead to obtain molecular descriptors such as EHOMO (energy of the highest occupied molecular orbital), ELUMO (energy of the lowest unoccupied molecular orbital), ΔE (energy gap) and μ (dipole moment). The global reactivity descriptors such as χ (electronegativity), η (hardness), S (softness) and ω (electrophilicity index) were derived using Koopman’s theorem and analyzed. We used the condensed Fukui function and softness indices, Mulliken population analysis for local reactivity study. The calculated results are consistent with the experimental data.

A Quantitative-Structure-Activity-Relationship (QSAR) model for the reaction rate constants of organic compounds during the ozonation process at different temperatures

The ozonation process is an effective method for removing hazardous wastes in water. To better characterize and understand the factors influencing the reaction rate constants of organic compounds during the ozonation process, a quantitative-structure–activity-relationship (QSAR) model was developed using the principal component analysis and multiple linear regression (PCA-MLR) method. In principal component analysis, five of the seven components were found to mechanistically and statistically affect the reaction rate constants. Component 1 was represented by the number of oxygen atoms (nO) and minimum value of bond order (BOn), component 2 was represented by the energy of the highest occupied molecular orbital (EHOMO), and component 3 and 4 were dominated by the largest change in the charge of each atom during nucleophilic attack (f(+)x) and the energy of the lowest unoccupied molecular orbital (ELUMO), respectively. The temperature (T) was the most important factor for component 7. The optimal model was lnkO3=4.102+0.007T-3.419BOn+1.765f(+)x+5.698ELUMO-4.016EHOMO-0.241nO, with the following evaluation index values: squared correlation coefficient (R2) = 0.916, internal validation (q2) = 0.895 and external validation (Qext2) = 0.962. Based on these evaluation indices, Y-randomization validation and the definition of the applicability domain, the optimal model was stable, robust and predictive. We anticipate that our work will provide a credible theoretical foundation for estimating the reaction rate constants for degradation of high-molecular weight organic compounds during ozonation over a temperature range from 25 to 60 °C.

IR study on the electrochemical generation of a nitro radical anion by a hepatotoxic N,N′-disubstituted benzimidazole-2-thione

In the course of our study on the hepatotoxicity of 1,3-disubstituted-1H-benzo[d]imidazole-2(3H)-thiones, we generated and characterized the radical anion of methyl 3-[3-(3-methoxy-3-oxopropyl)-5-nitro-2-thioxo-2,3-dihydro-1H-benzimidazol-1-yl]propanoate which shows the highest toxicity within the studied series. The reduction of the title compound was carried out electrochemically and the spectral and structural changes arising from the conversion were described based on IR spectra and DFT calculations. Repeated monitoring of IR spectra over time demonstrated successful generation of the radical anion accompanied by strong frequency decrease of NO stretching vibrations and increase of CN stretching vibration. The neutral compounds and the radical anion are characterized by coplanar orientation of the nitro group towards the aromatic system which most likely contributes to the observed toxicity. The structure of the radical anion shows extended electronic conjugation compared to the neutral compound. The NBO spin population analysis of the radical anion indicated that 0.707 of the odd electron is localized over the nitro group, while 0.293 is spread over the benzimidazole-2-thione fragment. Based on calculated energy of the lowest unoccupied molecular orbital (ELUMO) for the neutral compound, energy difference between the lowest unoccupied and the highest occupied molecular orbital (ΔEL−H), and adiabatic electron affinity (EA), it was estimated that the propensity of methyl 3-[3-(3-methoxy-3-oxopropyl)-5-nitro-2-thioxo-2,3-dihydro-1H-benzimidazol-1-yl]propanoate to generate a radical anion in biological systems would be comparable to that of nitrobenzene and nimesulide and much lower than those of nitrofurantoin.

Energy of the Lowest Unoccupied Molecular Orbital, Thiol Reactivity, and Toxicity of Three Monobrominated Water Disinfection Byproducts.

Disinfection of drinking water protects public health against waterborne pathogens. However, during disinfection, toxic disinfection byproducts (DBPs) are formed. Exposure to DBPs was associated with increased risk of bladder cancer in humans. DBPs are generated at concentrations below their carcinogenic potencies; it is unclear how exposure leads to adverse health outcomes. We used computational estimates of the energy of the lowest unoccupied molecular orbital (ELUMO) to predict thiol reactivity and additive toxicity among soft electrophile DBPs. Bromoacetic acid (BAA) was identified as non-thiol-reactive, which was supported by in chemico and in vitro data. Bromoacetonitrile (BAN) and bromoacetamide (BAM) were thiol-reactive. Genotoxicity induced by these compounds was reduced by increasing the thiol pool with N-acetyl L-cysteine (NAC), while NAC had little effect on BAA. BAN and BAM shared depletion of glutathione (GSH) or cellular thiols as a molecular initiating event (MIE), whereas BAA induces toxicity through another pathway. Binary mixtures of BAM and BAN expressed a potentiating effect in genotoxicity. We found that soft electrophile DBPs could be an important predictor of common mechanism groups that demonstrated additive toxicity. In silico estimates of ELUMO could be used to identify the most relevant DBPs that are the forcing factors of the toxicity of finished drinking waters.

Prediction of Log P of Halogenated Alkanes by Their ELUMO and Number of Chlorine and Carbon

Hydrophobicity, as measured by Log P, is an important molecular property in assessing toxicity and carcinogenicity of disinfection by-products (DBPs). With increasing public health concerns of DPBs, there are considerable benefits in developing Quantitative Structure Activity Relationship (QSAR) models, capable of accurately predicting Log P, which could be used in health risk assessment of DBPs. In this research, Log P values of 46 halogenated alkanes, as one class of DBP compounds, were used to develop QSAR models for this class. Three molecular descriptors, namely, Energy of the Lowest Unoccupied Molecular Orbital (ELUMO), Number of Chlorine (NCl) and Number of Carbon (NC) were used in Multiple Linear Regression (MLR) analysis. The QSAR models developed were validated according to the principles set up by the Organization for Economic Co-operation and Development (OECD). Model Applicability Domain (AD) of the developed QSAR models was defined and mechanisms were interpreted. Considering large number of halogenated alkane compounds, the established QSAR models performed very well in terms of goodness-of-fit, robustness and predictability. The predicted values of Log P of DBPs by the QSAR models have correlation coefficient R2 from 81 % to 98 % with the observed Log P. The leverage approach by Williams plot was applied to detect and remove outliers. As a result, the correlation coefficient, R2, of the QSAR models increased by approximately 2 % to 13 %, before and after removing the outliers, respectively. The developed QSAR model was statistically validated for its predictive power of Log P by the Leave-One-Out (LOO) and Leave-Many-Out (LMO) cross validation methods.

Quantitative Structure-Activity Relationships Study on the Rate Constants of Polychlorinated Dibenzo-p-Dioxins with OH Radical.

The OH-initiated reaction rate constants (kOH) are of great importance to measure atmospheric behaviors of polychlorinated dibenzo-p-dioxins (PCDDs) in the environment. The rate constants of 75 PCDDs with the OH radical at 298.15 K have been calculated using high level molecular orbital theory, and the rate constants (kα, kβ, kγ and kOH) were further analyzed by the quantitative structure-activity relationships (QSAR) study. According to the QSAR models, the relations between rate constants and the numbers and positions of Cl atoms, the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), the difference ΔEHOMO-LUMO between EHOMO and ELUMO, and the dipole of oxidizing agents (D) were discussed. It was found that EHOMO is the main factor in the kOH. The number of Cl atoms is more effective than the number of relative position of these Cl atoms in the kOH. The kOH decreases with the increase of the substitute number of Cl atoms.

Reduction of nitroaromatics sorbed to black carbon by direct reaction with sorbed sulfides.

Sorption to black carbons is an important sink for organic contaminants in sediments. Previous research has suggested that black carbons (graphite, activated carbon, and biochar) mediate the degradation of nitrated compounds by sulfides by at least two different pathways: reduction involving electron transfer from sulfides through conductive carbon regions to the target contaminant (nitroglycerin) and degradation by sulfur-based intermediates formed by sulfide oxidation (RDX). In this study, we evaluated the applicability of black carbon-mediated reactions to a wider variety of contaminant structures, including nitrated and halogenated aromatic compounds, halogenated heterocyclic aromatic compounds, and halogenated alkanes. Among these compounds, black carbon-mediated transformation by sulfides over a 3-day time scale was limited to nitroaromatic compounds. The reaction for a series of substituted nitroaromatics proceeded by reduction, as indicated by formation of 3-bromoaniline from 3-bromonitrobenzene, and inverse correlation of log kobs with energy of the lowest unoccupied molecular orbital (ELUMO). The log kobs was correlated with sorbed sulfide concentration, but no reduction of 3-bromonitrobenzene was observed in the presence of graphite and sulfite, thiosulfate, or polysulfides. Whereas nitroglycerin reduction occurred in an electrochemical cell containing sheet graphite electrodes in which the reagents were placed in separate compartments, nitroaromatic reduction only occurred when sulfides were present in the same compartment. The results suggest that black carbon-mediated reduction of sorbed nitroaromatics by sulfides involves electron transfer directly from sorbed sulfides rather than transfer of electrons through conductive carbon regions. The existence of three different reaction pathways suggests a complexity to the sulfide-carbon system compared to the iron-carbon system, where contaminants are reduced by electron transfer through conductive carbon regions.

New mediators for biosensors based on PQQ-dependent alcohol dehydrogenases

A set of 10 quinoidal compounds synthesized enzymatically using laccase from Coriolopsis byrsina GRB13 have been examined as redox mediators applicable for bioelectrocatalytic systems using two types of pyrroloquinoline quinone-dependent alcohol dehydrogenases – periplasmic (s-PQQ-ADH) and membrane-bound (m-PQQ-ADH). The efficiency of the biosensors have been evaluated for both types of enzymes and varied in range from 2×10−7A for Phenazine-2,3-diamine to 26×10−7A for 2-(3-Nitroanilino)-1,4-benzoquinone. Experimental data correlated with the molecular properties of mediators using results of ab initio quantum chemical calculations. The oxidation potential of mediators as well as the maximum current (Imax) of biosensors correlated with the calculated energy of the lowest unoccupied molecular orbital (ELUMO) of mediators. In the case of Imax, this result indicates the rate-limiting character of enzymatic mediator reduction in the overall process of biosensor response. The proposed approach demonstrates that the advance determination of molecular properties of potential mediators by ab initio quantum chemical calculations might be a useful instrument in the development process of the redox enzymes based biosensors.

The kinetics and QSAR of abiotic reduction of mononitro aromatic compounds catalyzed by activated carbon

The kinetics of abiotic reduction of mono-nitro aromatic compounds (mono-NACs) catalyzed by activated carbon (AC) in an anaerobic system were examined. There were 6 types of substituent groups on nitrobenzene, including methyl, chlorine, amino, carboxyl, hydroxyl and cyanogen groups, at the ortho, meta or para positions. Our results showed that reduction followed pseudo-first order reaction kinetics, and that the rate constant (logkSA) varied widely, ranging between −4.77 and −2.82, depending upon the type and position of the substituent. A quantitative structure–activity relationship (QSAR) model using 15 theoretical molecular descriptors and partial-least-squares (PLS) regression was developed for the reduction rates of mono-NACs catalyzed by AC. The cross-validated regression coefficient (Qcum2, 0.861) and correlation coefficient (R2, 0.898) indicated significantly high robustness of the model. The VIP (variable importance in the projection) values of energy of the lowest unoccupied molecular orbital (ELUMO) and the maximum net atomic charge on the aromatic carbon bound to the nitro group (QC-) were 1.15 and 1.01, respectively. These values indicated that the molecular orbital energies and the atomic net charges might play important roles in the reduction of mono-NACs catalyzed by AC in anaerobic systems.

Prediction of the Fate of Organic Compounds in the Environment From Their Molecular Properties: A Review

A comprehensive review of quantitative structure-activity relationships (QSAR) allowing the prediction of the fate of organic compounds in the environment from their molecular properties was done. The considered processes were water dissolution, dissociation, volatilization, retention on soils and sediments (mainly adsorption and desorption), degradation (biotic and abiotic), and absorption by plants. A total of 790 equations involving 686 structural molecular descriptors are reported to estimate 90 environmental parameters related to these processes. A significant number of equations was found for dissociation process (pKa), water dissolution or hydrophobic behavior (especially through the KOW parameter), adsorption to soils and biodegradation. A lack of QSAR was observed to estimate desorption or potential of transfer to water. Among the 686 molecular descriptors, five were found to be dominant in the 790 collected equations and the most generic ones: four quantum-chemical descriptors, the energy of the highest occupied molecular orbital (EHOMO) and the energy of the lowest unoccupied molecular orbital (ELUMO), polarizability (α) and dipole moment (μ), and one constitutional descriptor, the molecular weight. Keeping in mind that the combination of descriptors belonging to different categories (constitutional, topological, quantum-chemical) led to improve QSAR performances, these descriptors should be considered for the development of new QSAR, for further predictions of environmental parameters. This review also allows finding of the relevant QSAR equations to predict the fate of a wide diversity of compounds in the environment.

Evaluation on joint toxicity of chlorinated anilines and cadmium to Photobacterium phosphoreum and QSAR analysis

The individual IC50 (the concentrations causing a 50% inhibition of bioluminescence after 15min exposure) of cadmium ion (Cd) and nine chlorinated anilines to Photobacterium phosphoreum (P. phosphoreum) were determined. In order to evaluate the combined effects of the nine chlorinated anilines and Cd, the toxicities of chlorinated anilines combined with different concentrations of Cd were determined, respectively. The results showed that the number of chlorinated anilines manifesting synergy with Cd decreased with the increasing Cd concentration, and the number manifesting antagonism decreased firstly and then increased. The joint toxicity of mixtures at low Cd concentration was weaker than that of most binary mixtures when combined with Cd at medium and high concentrations as indicated by TUTotal. QSAR analysis showed that the single toxicity of chlorinated anilines was related to the energy of the lowest unoccupied molecular orbital (ELUMO). When combined with different concentrations of Cd, the toxicity was related to the energy difference (EHOMO−ELUMO) with different coefficients. Van der Waals’ force or the complexation between chlorinated anilines and Cd had an impact on the toxicity of combined systems, which could account for QSAR models with different physico-chemical descriptors.

Inhibitory Activity of Carbonyl Compounds on Alcoholic Fermentation by Saccharomyces cerevisiae

Aldehydes and acids play important roles in the fermentation inhibition of biomass hydrolysates. A series of carbonyl compounds (vanillin, syringaldehyde, 4-hydroxybenzaldehyde, pyrogallol aldehyde, and o-phthalaldehyde) were used to examine the quantitative structure-inhibitory activity relationship of carbonyl compounds on alcoholic fermentation, based on the glucose consumption rate and the final ethanol yield. It was observed that pyrogallol aldehyde and o-phthalaldehyde (5.0 mM) reduced the initial glucose consumption rate by 60 and 89%, respectively, and also decreased the final ethanol yield by 60 and 99%, respectively. Correlating the molecular descriptors to inhibition efficiency in yeast fermentation revealed a strong relationship between the energy of the lowest unoccupied molecular orbital (ELUMO) of aldehydes and their inhibitory efficiency in fermentation. On the other hand, vanillin, syringaldehyde, and 4-hydroxybenzaldehyde (5.0 mM) increased the final ethanol yields by 11, 4, and 1%, respectively. Addition of vanillin appeared to favor ethanol formation over glycerol formation and decreased the glycerol yield in yeast fermentation. Furthermore, alcohol dehydrogenase (ADH) activity dropped significantly from 3.85 to 2.72, 1.83, 0.46, and 0.11 U/mg at 6 h of fermentation at vanillin concentrations of 0, 2.5, 5.0, 10.0, and 25.0 mM correspondingly. In addition, fermentation inhibition by acetic acid and benzoic acid was pH-dependent. Addition of acetate, benzoate, and potassium chloride increased the glucose consumption rate, likely because the salts enhanced membrane permeability, thus increasing glucose consumption.

Toxicity profile of aromatic compounds towards Scenedesmus obliquus: a QSAR study

The parameterization of molecular hydrophobicity and electrophilicity, contributing to the overall toxicity of aromatic compounds, has been the subject of many quantitative structure−activity relationship (QSAR) studies. So far, hydrophobicity has been largely described in terms of the logarithm of the octanol−water partition coefficient (log P) and the molecular electrophilicity in terms of the energy of the lowest unoccupied molecular orbital (ELUMO), the maximum acceptor superdeocalizability (Amax), and the electrophilicity index (ω). Here, we report for the first time the parameterization of these properties in terms of cumulative interplay of multiple descriptors. The toxicity data of 68 compounds were compiled in terms of 50% population growth inhibition (pIGC50) of Scenedesmus obliquus. The comparison of the two QSARs (pIGC50 = 0.175ELUMO + 0.057log P + 0.363ω + 0.019V – 3.292, R2adj = 0.761 and pIGC50 = 0.368ELUMO + 0.146α + 0.258ω + 0.021V − 1.170, R2adj = 0.776) reveals that polarizability (α) is a superior descriptor to log P for parameterization of hydrophobicity, when used in conjunction with ELUMO, ω, and V, for profiling of the toxicity of the test compounds. The overall results indicate that ω and α are better descriptors of electrophilicity and hydrophobicity, respectively, for mapping the toxicity profile of aromatic derivatives towards the target organism.

A computational approach to the free radical polymerization kinetics of alkyl α‐hydroxymethacrylate monomers: A structure–reactivity relationship

ABSTRACTDensity functional theory calculations at the B3LYP/6–31+G(d) level were carried out for 16 alkyl α‐hydroxymethacrylate (RHMA) monomers, and the calculated quantum chemical descriptors were used to construct a quantitative structure–activity relationship model of the reactivity parameters of those monomers. A multiple regression analysis was adopted to predict the polymerization kinetics. The molecular descriptors used in this study are the Mulliken and APT charges of the backbone C atoms in proximity of the reactive center, the total dipole moment (µ), the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), the isotropic polarizability (α), the Mulliken atomic spin density (ρs), the ionization energy (IE), the electron affinity (EA), the resonance parameter (Res), the natural atomic orbital occupancies, and the bond distances of the bonds in the proximity to the reactive center of the RHMA monomers and their corresponding radicals. Among the various descriptors considered, the IE and EA of the monomers, the bond order of carbonyl double bond of monomer (BOCO), the resonance stabilization parameter of the monomeric radical, and the Mulliken atomic spin density (ρs) of C5 of the radical were found to be correlated (R2 = 0.9416) with the experimental rates of photopolymerization. The correlation with experiment is also satisfactory when additional monomers are included in the data set; a new correlation is thus generated (R2 = 0.9186). This study is expected to shed light on predicting the reactivities of RHMA monomers prior to their synthesis and to rank their photopolymerization rates based on their quantitative structural properties. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2375–2384

QSAR Analyzes for the Predictive Toxicity of Substituted Phenols and Anilines to Fish (<i>carp</i>)

A quantitative structure-activity relationship (QSAR) study for predicting the acute toxicity 96h - LC50 values of substituted anilines and phenols to carp is presented in this work. For this, the descriptors were obtained with DFT method at the B3LYP/6-311G** level using the Gaussian 03 software package. Afterwards the obtained parameters were taken as theoretical descriptors to establish a QSAR model for predicting -lgLC50. The model contains two variables, energy of the highest occupied molecular orbital (EHOMO) and energy of the lowest unoccupied molecular orbital (ELUMO), which suggest that the main effect on biological toxicity of phenols and anilines is the interaction of electrons between the molecules of organic chemicals. Besides, the model was further validated by variance inflation factors (VIF) and t-test, and show fine stabilities and predictive abilities, which can be used to predict -lgLC50 of these kinds of compounds.