Current Physical Chemistry - Volume 12, Issue 1, 2022

Finite-difference expressions for the chemical potential (negative electronegativity) and hardness (inverse softness) descriptors of molecular and donor-acceptor systems are summarized and chemically “biased” (informed) and “unbiased” (uninformed) estimates of charge-transfer (CT) descriptors in A(acid)-B(base) systems are reexamined. The former recognizes the chemical characteristics of reactants and the chemical-potential discontinuity, while in the latter no prior knowledge of such kind is used. The biased chemical potential and fragment hardness descriptors are interpreted in terms of the frontier-electron orbitals, and the equivalence of predictions in both treatments is demonstrated using the electronegativity- equalization principle. Two-state description of CT involves a statistical mixture of initial state |NCT = 0〉 = |A⁰, B⁰〉 of the polarized (mutually closed) reactants in R+ = (A+|B+), and one of admissible final states for the full electron transfer, |NCT| = 1, in the forward B⁰→A⁰ or reverse A⁰→B⁰ directions, leading to ion-pairs |B⁰→A⁰〉 = |NCT = 1〉 = |A−1, B⁺¹〉 and |A⁰→B⁰〉 = |NCT = −1〉 = |A+1, B−1〉. Parabolic interpolation between energies of the integral-N states identifies the process activation and reaction energies predicts the equilibrium amount of CT and stabilization energy it generates.

Background: Benzoyl thiourea derivatives linked to morpholine and piperidine have been reported to possess good antifungal activity. Objective: The aim of the study was to find the correlations between the quantum chemical calculations and the antifungal activity of the benzoyl thiourea derivatives linked to morpholine and piperidine. Methods: Optimization of six compounds BTP 1-3 and BTM 4-6 was carried out with DFT using B3LYP method utilizing 6-31G(d,p) basis set. The structural parameters of the compounds as molecular geometry, bond lengths, bond angles, atomic charges and HOMOLUMO energy gap have been investigated and compared with the reported experimental results. Results: A good correlation between the quantum chemical calculations and the antifungal activity of the benzoyl thiourea derivatives linked to morpholine and piperidine was found. Conclusion: The DFT study of benzoyl thiourea derivatives linked to morpholine and piperidine conducted with respect to their Quantum chemical parameters for evaluation of their antifungal activity showed good correlations between the antifungal activity and the quantum chemical parameters.

Aim: Corrosion of mild steel pipe line when exposed to dilute sulphuric acid is a very serious problem for people in the industry and they are in constant search of highly efficient corrosion inhibitors for acidic medium. For designing new corrosion inhibitors, a through knowledge of corrosion and adsorption mechanism is required. Background: Pitting, cracking and uniform types of corrosion are very common forms of corrosion in dilute sulphuric acid medium. A highly efficient acid corrosion inhibitor is required to minimize all these three forms of corrosion. Objective: The objective was to provide a solution for pitting, cracking, and uniform types of corrosion and to study corrosion and inhibition mechanisms so that highly efficient corrosion inhibitors can be designed. Methods: Polyvinyl pyrrolidone (PVP) was explored as a corrosion inhibitor for mild steel in 1.0 M H2SO4 by experimental and theoretical techniques. Experimental techniques used were impedance, weight loss, metallurgical microscopy, and polarization. Theoretical techniques used were DFT, MD simulation, Frontier molecular orbital, Langmuir, and Frumkin adsorption. Theoretical parameters like interaction energy, adsorption energy, Fukui function, chemical potential, electron density distribution, HOMO/LUMO eigenvalue, etc., help in understanding the mechanism of adsorption of PVP on the Fe (110) surface. Results: Experimental results were supported by theoretical studies. A linear relation was observed between PVP concentration and inhibition efficiency. A maximum of 85.92% inhibition efficiency was observed with a regression coefficient of 0.998. The pore length, the number of pits, and cracks intensity decrease with the concentration of PVP. The waste dilute H2SO4 after the weight loss study was investigated for its biocompatibility and was found to be within the acceptable limit. Conclusion: PVP was proved to be a highly efficient acid corrosion inhibitor for mild steel in 1.0 M H2SO4 medium.

Aims: This study aimed at determining the synthesis, DFT studies, and specific heat capacity (Cp) of azo dyes composed of derivatives of 2-aminothiazole and thymol. Background: To date, azo dyes have transitioned from the science of molecules to the science of materials very elegantly. 2-aminothiazole and thymol have a wide biological application window. Therefore, attempts have been made to couple these two biologically important organic frameworks via a diazotization strategy. Objective: The objective of this study was to explore thymol as a coupling partner for the synthesis of azo dyes via a diazotization strategy. Furthermore, the structures of the synthesized azo dyes have been confirmed using DFT calculations. In addition, thermal profiles (TGA-DSC) have been explored elegantly to calculate specific heat capacity (Cp) as a function of temperature for the synthesized azo dyes. Methods: A unit operation, i.e., diazotization, has been tuned very aptly for the formation of azodye framework based on 2-aminothymol and thymol. Thereafter, the thermal stability of the synthesized azo dyes has been addressed using TGA-DSC. Moreover, the Density Functional Theory has also been used to confirm vibrational frequencies of the synthesized azo dyes. Results: In the present work, the effect of electronic parameters on the melting temperature of the corresponding azo dyes has been comprehended with the help of DSC analysis. Specific heat capacity data as a function of temperature for the synthesized dyes have been reported for the first time. Conclusion: Melting behavior of the synthesized azo dyes is determined based on electronic effects with the help of thermal analysis. The specific heat capacity data can be helpful for the chemists, those engaged in chemical modelling, as well as for further docking studies. The structures of these synthesized azo dyes have been confirmed by performing DFT calculations, and to our delight, the comparison of both the experimental and calculated vibrational frequency data is found in good agreement with each other.

Aims: Kinetic study of iodination of propanone in different acidic medium by using colorimeter. Background: The kinetic experimentation of iodination of propanone has been done in presence of different acid such as sulphuric acid, hydrochloric acid and acetic acid. The rate law of the iodination of propanone in acidic medium is determined by observing the disappearance of the brownish yellow colour of iodine in aqueous solution. Objective: Preparation of standard solution, Determination of absorbance of iodine solution at λmax= 480 nm, Kinetic study of iodination of propanone at different acidic medium. Methods: The kinetic analysis of this reaction has been investigated by colorimetry. The extent of the reaction has been monitored by measuring the absorbance of reaction mixture after a suitable time interval. Results: The rate law expression has been determined to be rate = k [propanone]0^0.728 [acid]0. The rate of iodination of propanone in the presence of different acidic medium is in the order of H2SO4 > HCl > CH3COOH. Conclusion: The rate of the reaction has been found to be independent of the concentration of iodine, i.e., a zero-order reaction with respect to iodine; however, it depended upon the concentration of propanone and the acidic catalyst. In this experimental technique, the consumption of chemicals is minimal.

Background: The Fenton reaction is of growing interest due to its primary function in bodily processes and industrial waste disposal. However, the effects of alcohol on this reaction have not been addressed. Therefore, we analyze for the first time the role that catalytic concentrations of alcohols play in the Fenton reaction. Methods: The Fenton reaction was carried out by measuring oxidation-reduction potential and pH monitoring under dark conditions to avoid photochemical reactions. The reaction end point was established using the first derivative of plotting potential versus time. This point was also checked by the dichromate test for hydrogen peroxide detection. Gas-liquid chromatography was used to measure alcohol content. The Fenton reaction of glucose was performed first, and then each alcohol, including ethanol, methanol, iso-propanol, and terbutanol, was added separately in catalytic amounts, as well as the cyclic ether tetrahydrofuran. The reaction rate constants and the stability constants of each complex formed were measured. Results: Alcohols were shown to inhibit the Fenton reaction by forming iron-alcohol complexes. An iron-tetrahydrofuran complex was also formed. The crucial oxygen role in the functional group of alcohols and ethers is supported by a reaction with tetrahydrofuran. These results also explain the difficulties in the disposal of sugar-enriched alcoholic industrial effluents. Conclusion: Our findings show that alcohols, such as ethanol, methanol, iso-propanol, and ter-butanol at catalytic concentrations, slow down the Fenton reaction due to decreased iron availability by forming iron (II)-alcohol complexes. The method is also useful for calculating stability constants for iron-alcohol and iron-tetrahydrofuran complexes, which are not otherwise easy to assess.

Introduction: In January 1968, an Israeli submarine "Dakar" sank in the Mediterranean Sea. The Dakar’s wreckage was not found until May 1999, when it was located between the islands of Cyprus and Crete at depth more than 3,000 m by the Nauticos Corporation, the same company which found a British passenger liner "Titanic" that sank in the North Atlantic Ocean after it collided with an iceberg. The possibility to recover any existing remains of the crew members in the sunken submarine “Dakar” and to give them Jewish burial had been widely discussed in Israel. Background: The human bones consist of mineral and organic matrixes. Therefore, the solubility of the bones in seawater will depend on the behavior of these two matrixes. The main mineral component of human bones is a calcium phosphate mineral which is similar in composition and structure to minerals within the apatite group. Thus, the human bones are rigid body tissue consisting of biological cells embedded in an abundant, hard intercellular material. Objective: The main objective is to study the possibility of solubility of human bones after prolonged time in deep waters. Methods: The solubility of minerals in natural waters can be calculated from thermodynamic considerations provided that the equilibrium constants are known, and ionic activity coefficients can be obtained. Using the approaches developed by Pitzer's scientific school for ionic activity coefficients calculations it was demonstrated in this article that neither hydroxyapatite nor fluorapatite can be dissolved in seawater. Results: It is well known, according to various publications, that no skeleton remains were found in most cases of sunken ships wreckage in deep seawaters. The question is how this contradiction can be explained if mineral constituents of human bones could not be dissolved in seawater, but no skeletons have been found in sunken ships being prolonged time in deep depths. We assume that the reason for this phenomenon is that skeleton bones in addition to mineral matrix contain organic constituents which can be dissolved in seawater due to various natural biological and chemical processes. After the dissolution of the organic constitutes of the bones, the bones remains could not be preserved as a whole in sunk ships. Conclusion: It can be assumed that due to the dissolution of human bones' organic contents in seawater, human bodies’ remains cannot be found in most cases in sunken ships after a prolonged time in deep waters.