Refine Search

New Search

Results in Journal Open Journal of Physical Chemistry: 161

(searched for: journal_id:(2114337))
Page of 4
Articles per Page
by
Show export options
  Select all
Hebah M. Abdel-Wahab, Joseph W. Bozzelli
Open Journal of Physical Chemistry, Volume 11, pp 13-53; doi:10.4236/ojpc.2021.112002

Abstract:
Structures and thermochemical properties of these species were determined by the gaussian M-062x/6-31 + G (D, P) calculation enthalpies of formation for 19 fluorinated ethanol and some radicals were calculated with a popular Ab initio and density functional theory methods: The gaussian M-062x/6-31 + G (D, P) via several series of isodesmic reactions. Entropies (S298° in Cal·Mol-1 K-1) were estimated using the M-062x/6-31 + G (D, P) computed frequencies and geometries. Contributions of entropy, S°298, and heat capacities, Cp(T) due to vibration, translation, and external rotation of the molecules were calculated based on the vibration frequencies and structures obtained from the M-062x/6-31 + G (D, P) Density Functional Method. Potential barriers are calculated using M-062x/6-31 + G (D, P) density functional method and are used to calculate rotor contributions to entropy and heat capacity using integration over energy levels of rotational potential. Rotational barriers were determined and hindered internal rotational contributions for s298° - 1500°, and cp (t) were calculated using the rigid rotor harmonic oscillator approximation, with direct integration over energy levels of the intramolecular rotation potential energy curves. Thermochemical properties of fluorinated alcohols are needed for understanding their stability and reactions in the environment and in thermal process.
Panagis G. Papadopoulos, Christopher G. Koutitas, Christos G. Karayannis, Panos D. Kiousis, Yannis N. Dimitropoulos
Open Journal of Physical Chemistry, Volume 11, pp 1-11; doi:10.4236/ojpc.2021.111001

Abstract:
A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the battery are considered. A simple algorithm, with variable time step-length Δt, is presented, for proposed model. The model is first applied to Daniel cell, in order to clarify concepts and principles of battery operation. It is found that initial pinching, in time-history curve of voltage E-t, is due to initial under-concentration of product ion. Then, model is applied to a lead-acid battery. In absence of an ion product, and in order to construct nominator of Nernst ratio, such an ion, with coefficient tending to zero, is assumed, thus yielding unity in nominator. Time-history curves of voltage, for various values of internal resistance, are compared with corresponding published experimental curves. Temperature effect on voltage-time curve is examined. Proposed model can be extended to other types of batteries, which can be considered as having aqueous electrolytes, too.
Augustus Newton Ebelegi, Nimibofa Ayawei, Donbebe Wankasi
Open Journal of Physical Chemistry, Volume 10, pp 166-182; doi:10.4236/ojpc.2020.103010

Abstract:
A complete study of adsorption processes will be less complete if the structure and dynamics of its different elements and how they interact is not well captured. Therefore, the extensive study of adsorption thermodynamics in conjunction with adsorption kinetics is inevitable. Measurable thermodynamic properties such as temperature equilibrium constant and their non-measurable counterparts such as Gibbs free energy change, enthalpy, entropy etc. are very important design variables usually deployed for the evaluation and prediction of the mechanism of adsorption processes.
André Tigori Mougo, Kouyaté Amadou, Kouakou Victorien, Marius Niamien Paulin, Trokourey Albert, Mougo André Tigori, Amadou Kouyaté, Victorien Kouakou, Paulin Marius Niamien, Albert Trokourey
Open Journal of Physical Chemistry, Volume 10, pp 139-157; doi:10.4236/ojpc.2020.103008

Abstract:
The theoretical study of chlorpropamide, tolazamide and glipizide was carried out by the Density Functional Theory (DFT) at B3LYP/6-31G(d) level. This study made it possible to determine the global reactivity parameters in order to better understand the interactions between the molecules studied and the copper surface. Then, the determination of local reactivity indices (Fukui functions and dual descriptor) on these molecules resulted in the precision on the most probable centers of nucleophilic and electrophilic attacks within each molecule. The results obtained, show that chloropropamide, tolazamide and glipizide can be good inhibitors against copper corrosion. Thus, the mechanism of copper corrosion inhibition of these compounds in nitric acid solution has been explained by means of theoretical calculations.
Mizukami Yoshihiro, Yoshihiro Mizukami
Open Journal of Physical Chemistry, Volume 10, pp 158-165; doi:10.4236/ojpc.2020.103009

Abstract:
We performed density functional theory (DFT) calculations for ribonucleotides and active triphosphate metabolites of candidate drugs against Coronavirus disease 2019 (Covid-19). Frontier orbitals (highest occupied molecular orbital and lowest unoccupied molecular orbital) at optimized structure of each molecule were obtained. T-705RTP (active triphosphate metabolite of favipiravir) and cytidine triphosphate (CTP) have similar shapes of frontier orbitals. We also obtained similar shapes of frontier orbitals among dihydroxy GS-441524 triphosphate (GS-441524 is an active triphosphate metabolite of remdesivir) and adenosine triphosphate (ATP). From a theoretical viewpoint, we suggest T-705RTP is a CTP analogue and dihydroxy GS-441524 triphosphate is an ATP analogue.
K. Elttaib, A. Benhmid
Open Journal of Physical Chemistry, Volume 10, pp 87-98; doi:10.4236/ojpc.2020.102005

Abstract:
The gravimetric analysis of electrodeposited nickel is demonstrated using electrochemical quartz crystal microbalance (EQCM) where the nickel coatings come from a solution of the metal chloride salt separately in either a1choline chloride: 2 ethylene glycol (ethaline) or 1 choline chloride: 2 urea (reline) based ionic liquid. The possibility of adapting the Quartz Crystal Microbalance EQCM (which measures the mass attached to the electrode) to probe kinetics of electrochemically-driven solid state phase transformations has been explored in a Ni electrodeposition in absence and presence of complexing agents ethylene diamine en and acetylacetonate acac from both electrolytes ethaline and reline. The study shows that the current efficiency and the rate of deposition of nickel coatings obtained from ethaline and reline baths in absence of brighteners en and acac are different, and the addition of en and acac to both ionic liquid solutions results in a significant decrease current. And the associated growth rate will also be decreased, suggesting that the en acac stops the formation and growth of Ni nuclei. This suggests that the mechanism of growth is changed.
Khairia M. Al-Ahmary, Fatimah A. AlShehri, Faten M. Atlam, Mohamed K. Awad
Open Journal of Physical Chemistry, Volume 10, pp 1-32; doi:10.4236/ojpc.2020.101001

Abstract:
A charge transfer hydrogen bonded complex between the electron donor (proton acceptor) 2-amino-4,6-dimethylpyridine with the electron acceptor (proton donor) chloranilic acid has been synthesized and studied experimentally and theoretically. The stability constant recorded high values indicating the high stability of the formed complex. In chloroform, ethanol, methanol and acetonitrile were found the stoichiometric ratio 1:1. The solid complex was prepared and characterized by different spectroscopy techniques. FTIR, 1H and 13C NMR studies supported the presence of proton and charge transfers in the formed complex. Complemented with experimental results, molecular modelling using the density functional theory (DFT) calculations was carried out in the gas, chloroform and methanol phases where the existence of charge and hydrogen transfers. Finally, a good consistency between experimental and theoretical calculations was found confirming that the applied basis set is the suitable one for the system under investigation.
Robert A. Sizov
Open Journal of Physical Chemistry, Volume 10, pp 48-67; doi:10.4236/ojpc.2020.101003

Abstract:
The detection by the author of real magnetic charges, as well as true antielectrons in of atomic structures allowed him to establish that atomic shells, as well as shells of nucleons are electromagnetic, and not electronic. Namely electromagnetic shells are the sources of gravitational field which is the vortex electromagnetic field. The elementary source of gravitational field is the electromagnetic quasiparticle (S-Graviton) which consists of two coupled dipoles (the magnetic and electric) rotating in antiphase in the same atomic or nucleonic orbit. Electrons in atomic shells are rigidly embedded in the compositions of S-Gravitons and, as a rule, cannot individually participate, for example, in processes of interatomic chemical bonding. Depending on the vector conditions the gravitational fields can be both paragravitational (PGF) so and ferrogravitational (FGF). The overwhelming number of atomic shells and all shells nucleons emit PGF. Between the masses (bodies, atoms, nucleons, etc.) emitting of PGF is realized a force of gravitational “Dark energy” pressing masses to each other. It is the compression of masses by forces of the gravitational “Dark energy” that lies at basis Physics of chemical bond. Depending on implementation in atoms of the effects intra-atomic gravitational shielding/lensing (IAGS/L) discovered and investigated by the author, the gravitational interatomic bonding mechanisms are divided into two groups: non-covalent bonds (IAGS effect) and covalent bonds (IAGL effect). Within the framework of the gravitational bond mechanism of the latter group which is implemented with participation paragravitational orbitals, such chemical concept as valence acquires a real physical meaning. The replacing the erroneous electronic concept of chemical bonding by the gravitational concept implies replacing the notion “electronegativity” of element by the notion the “gravitational activity” while maintaining existing quantitative ability of atoms in molecules to attract atoms of other elements.
Paul Laffort
Open Journal of Physical Chemistry, Volume 10, pp 117-137; doi:10.4236/ojpc.2020.102007

Abstract:
An experimental characterization of the Van der Waals forces involved in volatile organic compounds (VOC) dissolved into stationary phases of gas liquid chromatography (GLC) has been started at the beginning of the seventies. This field has been reactivated from 1994 thanks to a fruitful cooperation between our CNRS team and the group of Ervin Kováts at the Federal Polytechnic School of Lausanne. The applied strategy can be summarized, in the first instance, as the experimental measurement of accurate and superabundant mutual affinities of a limited number of VOC and stationary phases and their processing using an original tool named Multiplicative Matrix Analysis (MMA). Then, in the second stage, the obtained results have been compared with molecular properties well established, as the Van der Waals molecular volume, the refraction index and the polar surface area (PSA), in order to get generalized values for any compound. The present study summarizes the positive results developed in our three last papers on this topic (2013, 2016 and 2018), as well as the attempt to overcome the negative ones using enthalpies of vaporization.
Panagis G. Papadopoulos, Christopher G. Koutitas, Panos D. Kiousis, Christos G. Karayannis, Yannis N. Dimitropoulos
Open Journal of Physical Chemistry, Volume 10, pp 99-116; doi:10.4236/ojpc.2020.102006

Abstract:
A simple algorithm is proposed for step-by-step time integration of stiff ODEs in Chemical Kinetics. No predictor-corrector technique is used within each step of the algorithm. It is assumed that species concentrations less than 10-6 mol·L-1 do not activate any chemical reaction. So, within each step, the time steplength Δt of the algorithm is determined from the fastest reaction rate maxR by the formula Δt = 10-6mol·L-1/max R. All the reversible elementary reactions occur simultaneously; however, by a simple book-keeping technique, the updating of species concentrations, within each step of the algorithm, is performed within each elementary reaction separately. The above proposed simple algorithm for Chemical Kinetics is applied to a simple model for hydrogen combustion with only five reversible elementary reactions (Initiation, Propagation, First and Second Branching, Termination by wall destruction) with six species (H2, O2, H, O, HO, H2O). These five reversible reactions are recommended in the literature as the most significant elementary reactions of hydrogen combustion [1] [2]. Based on the proposed here simple algorithm for Chemical Kinetics, applied to the global mechanism of proposed five reversible elementary reactions for hydrogen combustion, a simple and short computer program has been developed with only about 120 Fortran instructions. By this proposed program, the following are obtained: 1) The total species concentration of hydrogen combustion, starting from the sum of initial reactants concentrations [H2] + [O2], gradually diminishes, due to termination reaction by wall destruction, and tends to the final concentration of the product [H2O], that is to the 2/3 of its initial value, in accordance to the established overall stoichiometric reaction of hydrogen combustion 2H2 + O2 → 2H2O. 2) Time-histories for concentrations of main species H2, O2, H, H2O of hydrogen combustion, in explosion and equilibrium regions, obtained by the proposed program, are compared to corresponding ones obtained by accurate computational studies of [3]. 3) In the first step of the algorithm, the only nonzero species concentrations are those of reactants [H2], [O2]. So, the maximum reaction rate is that of the forward initiation reaction max R = Rif = kif[H2] [O2], where the rate constant kif is very slow. Thus, the first time steplength Δt1 = 10-6mol·L-1/max R results long in sec. After the first step, the sequences of all the following Δt’s are very short, in μsec. So, the first time steplength Δt1 can be considered as ignition delay time. 4) It is assumed that explosion corresponds to ignition delay time Δt1 t1 = 10 sec., can be considered as explosion limit curve. This curve is compared to the corresponding one obtained by the accurate computational studies of [2].
Khairia M. Al-Ahmary, Ashwaq T. Alharbi
Open Journal of Physical Chemistry, Volume 10, pp 33-47; doi:10.4236/ojpc.2020.101002

Abstract:
Studying of charge-transfer (CT) and proton transfer interactions is essential due to their important role in many biological field and industrial applications. The current work will add more information’s about the nature of interaction between 3,5-diamino-1,2,4-triazole (DAT) and 6-methyl-1,3,5-triazine-2,4-diamine (MTDA) with 3,6-dichloro-2,5-dihydroxy-p-benzoquinone (chloranilic acid CLA) which was studied spectrophotometrically in Ethanol (EtOH) and Methanol (MeOH) solvents at different temperatures. The molecular composition of the formed complexes was studied by applying continuous variation and spectrophotometric titration methods and found to be 1:1 charge transfer complex for both Complex (DAT:CLA) and (MTDA:CLA) which are produced. Minimum-Maximum absorbance’s method has been applied to calculate the formation constant KCT and molecular extinction coefficient (ε); they recorded high values confirming high stability of the produced complexes. Oscillator strength (f), transition dipole moment (μ), ionization potential (IP) and dissociation energy (W) of the formed CT-complexes were also determined and evaluated; they showed solvent dependency. It is concluded that the formation constant (KCT) of the complexes is found to depend on the nature of both electron acceptor and donors and on the polarity of solvents.
Geoffroy Auvert
Open Journal of Physical Chemistry, Volume 10, pp 68-85; doi:10.4236/ojpc.2020.101004

Abstract:
A decrease in temperature will eventually turn a gas into liquid and then into a solid. Each of these phase change shows a higher degree in cohesion of molecules. While it is usually admitted that molecules in solids form additional connections, the cohesion of molecules in liquids is usually explained by changes in kinetics of molecules. Given that the density of a solid is nearly the same than that of a liquid, the present paper assumes a different stand and considers that connections between molecules must be similar in liquids and in solids. The difference between gas, in which molecules are entirely loose, and liquid, is therefore the presence of an additional connection between gaseous molecules. This paper describes how and where these connections are built with the help of a few rules and a “specific periodic table for liquids”. The coherence of this approach is reinforced by its capacity to explain phase change of forty well-known molecules containing inorganic and organic elements.
Balqees Suliman Alshareef
Open Journal of Physical Chemistry, Volume 10, pp 197-204; doi:10.4236/ojpc.2020.104012

Abstract:
Significant interest has been focused on graphene materials for their unique properties as Hydrogen storage materials. The development of their abilities by modifying their configuration with doped or decorated transition metals was also of great interest. In this work, using the DFT/B3LYP/6-31G/LanL2DZ level of theory, graphene sheet (GS) as one of the materials of interest was doped with two transition metals, Osmium (Os) and Tungsten (W). Two active sites on the GS were tested (C4 and C16) resulted into adsorbed systems, [email protected] and [email protected] C16 position showed the largest adsorption energy compared to that at C4. Therefore, C4 was replaced by the two metals and two adsorbed systems were formed: [email protected] and [email protected] The binding energy of [email protected] was found to be greater than that of [email protected]
Open Journal of Physical Chemistry, Volume 9, pp 33-50; doi:10.4236/ojpc.2019.92003

Abstract:
The present work illustrates a predictive method, based on graph theory, for different types of energy of subatomic particles, atoms and molecules, to be specific, the mass defect of the first thirteen elements of the periodic table, the rotational and vibrational energies of simple molecules (such as , H2, FH and CO) as well as the electronic energy of both atoms and molecules (conjugated alkenes). It is shown that such a diverse group of energies can be expressed as a function of few simple graph-theoretical descriptors, resulting from assigning graphs to every wave function. Since these descriptors are closely related to the topology of the graph, it makes sense to wonder about the meaning of such relation between energy and topology and suggests points of view helping to formulate novel hypotheses about this relation.
Julian M. Menter, La Toya Freeman, Ortega Edukye
Open Journal of Physical Chemistry, Volume 9, pp 51-59; doi:10.4236/ojpc.2019.92004

Abstract:
The extracellular matrix (ECM) is the non-cellular component present within all tissues and organs, providing not only essential physical scaffolding for the cellular constituents and initiating crucial biochemical and biomechanical cues, required for tissue morphogenesis, differentiation and homeostasis. Roughly divided into two groups, these are 1) the main fibrous ECM proteins: collagens, elastins, fibronectins and laminins. 2) Classification of proteoglycans (PGs) is based on their location and binding. Although many different molecular interactions are possible, they depend on the cells’ condition (i.e. “Normal”, Aged, Wounded/Fibrotic, and cancerous). There is little or no data that addresses the influence of the surrounding ECM on dityrosine formation. As a simpler model, we have replaced total PG with hyaluronan (HA) and have used purified calf-skin collagen tyrosine, which forms dityrosine (A2) under 254 nm UV in buffered solution and (near) physiological temperatures. Our results reveal a complicated temperature dependence involving factors relating to collagen HA structure, and collagen’s photochemical activation parameters.
Panagis G. Papadopoulos, Panos D. Kiousis, Christos G. Karayannis
Open Journal of Physical Chemistry, Volume 9, pp 13-32; doi:10.4236/ojpc.2019.91002

Abstract:
Aim of this work is to try to explain, on a Rational basis, some equations of Electro-Magnetism, which are based on Experimental data. Any Electric Field can produce a Field of many small Electric Dipoles, continuously distributed in space. In a region, where the Electric Field is constant, in direction and magnitude, all the small Dipoles are parallel to the Electric Field, and are represented by a single, long, parallel to them, fixed in space, Electric Dipole, which is here called Compass. An Alternating current, in a straight Conductor, is studied, by a simple, short computer program, for step-by-step nonlinear dynamic analysis. It is found that, only an Alternating current, not a direct current, can produce an Electric Dipole, in a straight Conductor. The two above Dipoles (Compass-Conductor) are assumed with equal lengths ℓ, lying on two skew lines, perpendicular to each other, at a distance ℓ√2, thus forming, by their four ends, a Regular Tetrahedron, with side length ℓ. Repulsion, between Like Charges, obeys the simple Coulomb Electro-Static law. Whereas Interaction (Attraction or Repulsion), between Unlike Charges, obeys a more accurate Lennard-Jones law. The analysis of Dipole-Dipole (Compass-Conductor) Interaction is performed by hand calculator. The only out-of-balance forces, in the regular Tetrahedron, acting on the Rigid Conductor, are the so-called magnetic forces. Their direction is found, in a simple Rational way, with help of Regular Tetrahedron, without recoursing to a “right-hand-rule”. The proposed model is applied to 1) The force acting on an Electric Charge moving in a magnetic field. 2) The force acting on a Current carrying straight Conductor, due to a magnetic field. 3) The magnetic fields created around a Current carrying straight Conductor. In these applications, proposed model gives reasonable results. Particularly, in third application, results, obtained by proposed model, are found in satisfactory approximation with corresponding ones, obtained by an empirical formula, based on relevant Experimental observations of H.-C. Oersted and A.-M. Ampère. So, the reliability of proposed model is checked. Position and direction of magnetic field vector coincide with those of a corresponding fixed Compass of a constant Electric Field. Main point of present work is that, without introducing the concept of a magnetic field vector, by combining field of dipoles, produced by an electric field, with dipole of an alternating current carrying conductor, the magnetic forces can be determined.
Pieter Broer Van Der Weg
Open Journal of Physical Chemistry, Volume 9, pp 126-169; doi:10.4236/ojpc.2019.93008

V. P. Malyshev, A. M. Makasheva
Open Journal of Physical Chemistry, Volume 9, pp 107-125; doi:10.4236/ojpc.2019.93007

Mamadou S. Ba, Lat G. Ndiaye, Issakha Youm
Open Journal of Physical Chemistry, Volume 9, pp 170-181; doi:10.4236/ojpc.2019.93009

Carlos Tepech-Carrillo, Roxana Licona-Ibarra, J. Francisco Rivas-Silva, Antonio Flores-Riveros
Open Journal of Physical Chemistry, Volume 9, pp 1-12; doi:10.4236/ojpc.2019.91001

Abstract:
In this study, Density Functional Theory including a dispersion correction is employed to model and analyze the structural, electronic and local reactivity of the (100) surface of felodipine. The surface energy calculated at the Generalized Gradient Approximation (GGA) level, along with plane waves as basis set and ultrasoft pseudopotentials, shows that the (100) surface is the most stable as compared to the (010) and (110) ones. In particular, we have focused on performing a quantitative study of the reactivity of the surface by means of the Fukui function and through the HOMO and LUMO populations. Our results can be related to some applications in the pharmaceutical chemistry of this compound.
Henk M. Buck
Open Journal of Physical Chemistry, Volume 9, pp 182-191; doi:10.4236/ojpc.2019.93010

Abstract:
An electron-addition, under single-crystal conditions, to pentavalent phosphorus compounds as Cl-P (=O, S) Y, Z with the P-Cl bond as electron-accepting group, is selected as an additional model for SN2(P) like reactions. It is demonstrated that the geometric information stored in the tetrahedral configuration (substrate) can be transmitted in the corresponding trigonal bipyramidal (TBP) state for nucleophilic substitution. In this article, we focus on these specific mechanistic aspects of carbon and phosphorus. We consider our study as a contribution to the significance of these (bio)chemical intermediates.
I. A. Ar’Ev
Open Journal of Physical Chemistry, Volume 9, pp 204-215; doi:10.4236/ojpc.2019.94012

Abstract:
Earlier it was shown by different authors that there are cavities (vacancies, holes) in any liquid. The cavities should play a prominent role in dissolution processes. Nevertheless this fact was ignored in previous model of dissolution. The sizes of the cavities in different solvents containing benzene molecules were determined using solvent induced spectral shift method. The measurements of S1←S0 benzene transition spectral shifts permit to conclude that 1) macroscopic excess volumes play an almost negligible role in processes of benzene dissolution in very different solvents and 2) the minimal size of the cavity in water able to accommodate benzene molecule coincides with the solute size. Generalization of this conclusion to other nonpolar aromatics leads to evaluation contraction of the solutes under aqueous solvent influence permits to predict the solubility values of other aromatics in water and to evaluate effect of enhancement hydrate cell around these molecules on solubility.
Yayin Fang, Jamiya Kirkland, Isis J. Amaye, Patrice Jackson-Ayotunde, Matthew George Jr
Open Journal of Physical Chemistry, Volume 9, pp 241-257; doi:10.4236/ojpc.2019.94015

Abstract:
Epilepsy is described as the most common chronic brain disorder. A typical symptom of epilepsy results in uncontrolled convulsions caused by temporary excessive neuronal discharges. Although several new anticon-vulsants have been introduced, some types of seizures have still not been adequately controlled with these new and current therapies. There is an urgent need to develop new anticonvulsant drugs to control the many different types of seizures. Many studies have shown that the epilepsies involve more than one mechanism and therefore may be responsible for the various types of observed seizures. Recently reported studies have shown that a group of newly synthesized 6 Hz active anticonvulsant fluorinated N-benzamide enaminones exhibited selective inhibitions of voltage-gated sodium (Nav) channels. Nav channels are responsible for the initial inward currents during the depolarization phases of the action potential in excitable cells. The activation and opening of Nav channels result in the initial phases of action potentials. We hypothesize that there is an essential pharmacophore model for the interactions between these enaminones and the active sites of Nav channels. The research reported here is focused on molecular docking studies of the interactions that occur between the fluorinated N-benzamide enaminones and the Nav channels. These studies may open an avenue for designing anticonvulsant drugs by inhibiting Nav channels.
Raghad Alajlani, Amal Alssadi
Open Journal of Physical Chemistry, Volume 9, pp 216-220; doi:10.4236/ojpc.2019.94013

Abstract:
Many of the technology and computational chemistry applications are used to study drugs and their biological effects. Flutab® drug contains Paracetamol, Diphenhydramine and Pseudoephedrine. Ab-initio calculations were performed at DFT/B3LYP and HF methods with three basis sets, namely, STO-3G, 3-21G, and 6-31G(d) in order to calculate the dipole moments of the three constituents of Flutab® drug. The Diphenhydramine compound was found to be the most stable constituent, with the lowest value of dipole moment.
Sebastiano Tosto
Open Journal of Physical Chemistry, Volume 9, pp 60-87; doi:10.4236/ojpc.2019.92005

Abstract:
The paper shows that the second law of thermodynamics and Pauli principle are implications of the Bell inequality.
Alexander Billiot, Yayin Fang, Kevin F. Morris
Open Journal of Physical Chemistry, Volume 9, pp 221-240; doi:10.4236/ojpc.2019.94014

Abstract:
The enantiomers of chiral drugs often have different potencies, toxicities, and biochemical properties. Therefore, the FDA and other worldwide regulatory agencies require manufactures to test and prove the enantiomeric purity of chiral drugs. Amino acid based molecular micelles (AABMM) have been used in chiral CE separations since the 1990’s because of their low environmental impact and because their properties can easily be tuned by changing the amino acids in the chiral surfactant head groups. Using molecular dynamics simulations to investigate the structures and properties of AABMM is part of an ongoing study focusing on investigating and elucidating the factors responsible for chiral recognition with AABMM. The results will be useful for the proper design and selection of more efficient chiral selectors. The micelles investigated contained approximately twenty covalently linked surfactant monomers. Each monomer was in turn composed of an undecyl hydrocarbon chain bound to a dipeptide headgroup containing of all combinations of L-Alanine, L-Valine, and L-Leucine. These materials are of interest because they are effective chiral selectors in capillary electrophoresis separations. Molecular dynamics simulation analyses were used to investigate how the sizes and positions of the headgroup amino acid R-groups affected the solvent accessible surface areas of each AABMM chiral center. In addition, headgroup dihedral angle analyses were used to investigate how amino acid R-group size and position affected the overall headgroup conformations. Finally, distance measurements were used to study the structural and conformational flexibilities of each AABMM headgroup. All analyses were performed in the context of a broader study focused on developing structure-based predictive tools to identify the factors responsible for a) self-assembly, b) function, c) higher ordered structure and d) molecular recognition of these amino acid based molecular micelles.
Yapi Serge Brou, Nagnonta Hippolyte Coulibaly, N’Guessan Yao Silvère Diki, Juan Creus, Albert Trokourey
Open Journal of Physical Chemistry, Volume 9, pp 193-203; doi:10.4236/ojpc.2019.94011

Abstract:
Inhibitive properties of NAC and NAM as well as their mixture have been investigated in two different corrosive media through potentiodynamic polarization and electrochemical impedance spectroscopy at 298 K. These electrochemical measurements indicate that the inhibition efficiency increases with the concentration for each of the inhibitors used separately as well as for their mixture. In both cases, the combination behaves as mixed type inhibitor with a great cathodic tendency. NaCl 3.5% highlights an antagonist effect of NAM which reduces the effectiveness of NAC whereas HNO3 1M shows a synergistic effect between them.
Open Journal of Physical Chemistry, Volume 8, pp 1-14; doi:10.4236/ojpc.2018.81001

Abstract:
Innovative viewpoint on the older topic of the van der Waals forces, is of interesting and significant issue to be concerned in both the fields related to the fundamental investigation and thus valuable in guiding the new physiochemical phenomena and processes for both academic research and practical applications. The intermolecular Van der Waals forces involved in solutions have been recently deeply reconsidered as far as the solute side is concerned. More precisely, the solute descriptors (or parameters) experimentally established, have been accurately related to molecular features of a Simplified Molecular Topology. In the present study, an equivalent result is reached on the solvent side. Both experimental parameters have been obtained simultaneously in previous Gas Liquid Chromatographic studies for 121 Volatile Organic Compounds and 11 liquid stationary phases, via an original Multiplicative Matrix Analysis. In that experimental step, five groups of forces were identified, two of hydrogen bonding and three of Van der Waals: 1) dispersion (London), 2) orientation or polarity strictly speaking (Keesom), and 3) induction-polarizability (Debye). At this stage, an attempt of characterization the solvent parameters via the SMT procedure has been limited to those related to the Van der Waals forces, those related to the hydrogen bonding being for now left aside.
Panagis G. Papadopoulos, Christopher G. Koutitas, Yannis N. Dimitropoulos, Elias C. Aifantis
Open Journal of Physical Chemistry, Volume 8, pp 33-56; doi:10.4236/ojpc.2018.82003

Romanus N. Njong, Bridget N. Ndosiri, Emmanuel N. Nfor, Offiong E. Offiong
Open Journal of Physical Chemistry, Volume 8, pp 15-32; doi:10.4236/ojpc.2018.81002

Abstract:
The inhibition performance of 1-hydralazinophthalazine (HPZ) (1), and synthesized1-(2-[(5-methylfuran-2-yl)methylene)] hydrazono) phthalazine (MFHPZ) (2), 1-(phthalazin-1(2H)-one) [(pyridin-2-yl) ethylidene] hydrazone (ACPHPZ) (3) and (2-acetylthiophene hydrazono) phthalazine (ACTHPZ) (4) has been investigated for mild steel in 1 M HCl. Compound 4 shows maximum inhibition efficiency of 93% at 5.0 × 10-3 M concentration. The evaluation of thermodynamics and activation parameters indicated spontaneous adsorption of the inhibitor molecules which takes place through chemisorption. The adsorption of 3 and 2 follows Langmuir adsorption isotherm and Temkin adsorption isotherm for 4 and 1. The inhibitor efficiency was of the order 4 > 3 > 1 > 2. Impedance study for the representative inhibitor compounds 4 and 3 showed that decrease in charge transfer resistance is responsible for effective protection of mild steel surface by the tested inhibitor.
Rabab S. Jassas, Ahmed Fawzy, Rami J. Obied, Mohammed A. S. Abourehab,
Open Journal of Physical Chemistry, Volume 7, pp 35-49; doi:10.4236/ojpc.2017.72004

Abstract:
Oxidation kinetics of fluorene (Fl) and its halogenated derivatives, namely, 2,7-dichlorofluorene (Fl-Cl), 2,7-dibromofluorene (Fl-Br) and 2,7-diiodofluorene (Fl-I), by permanganate ion in both perchloric and sulfuric acid media have been investigated using conventional spectrophotometric technique. In both acidic media, the reactions manifested first order kineticsin [permanganate] and less than unit order each in [reductants] and [acid]. Increasing ionic strength had no effect on the oxidation rates. Oxidation rates of fluorenes in perchloric acid were higher than those in sulfuric acid and the order of the oxidation rates was: Fl > Fl-I > Fl-Br > Fl-Cl. Final oxidation products were identified by GC/MS and FT-IR analyses in all cases as 9H-fluorenone derivatives. Reaction constants as well as activation parameters of the second order rate constants were also evaluated.
Sebastiano Tosto
Open Journal of Physical Chemistry, Volume 7, pp 89-121; doi:10.4236/ojpc.2017.73007

Abstract:
The paper introduces a theoretical model aimed to calculate the ionization energies of many electron atoms and their ions. The validity of the model, which implements the statistical formulation of the quantum uncertainty to infer a simple formula of ionization energy, has been already proven in a previous paper comparing systematically experimental and calculated values for elements with atomic numbers 2≤Z≤29, whose electron configurations include all ions with numbers ne of electrons 2≤ne≤Z. The present paper enhances and extends the results previously obtained; the approach is now generalized to include even the transition elements and in particular the lanthanides and actinides. The validity of the proposed model is proven examining all experimental data of ionization energies of these elements and their ions available in literature.
Geoffroy Auvert
Open Journal of Physical Chemistry, Volume 7, pp 72-88; doi:10.4236/ojpc.2017.72006

Abstract:
The recently introduced even-odd rule has been shown to successfully represent chemical structures of ions and molecules. While comparing available drawings in the scientific literature with the list of compounds predicted by the even-odd rule, it became however obvious that existing compounds are fewer than expected. Several predicted compounds involving many covalent bonds have apparently never been experimentally observed. Neutral oxygen for instance is expected to have 6 valence electrons, whereas oxygen can only build a maximum of two bonds, as in water. This specificity is observed for elements in the top-right corner of the periodic table. For compounds to contain only single covalent bonds, and thus follow the even-odd rule, further explanations are necessary. The present paper proposes that those specific elements experience a transfer of electrons from the valence shell into the inner shell, making them unavailable for further bonding. These elements will be described as organic, hereby providing a clear and hopefully unifying definition of the term. In opposition, inorganic elements have a constant inner shell no matter their electrical state or the number of bonds they maintain. More than 70 compounds involving 11 elements of the main group are studied, revealing a progression from fully inorganic elements at the left of the periodic table to fully organic elements. The transition between inorganic or organic elements is made of few elements that take an organic form when negatively charged; they are labelled semi-organic. The article concludes that the fully organic elements of the main group are Oxygen and Fluorine, whereas semi-organic elements are more numerous: C, N, S, Cl, Se, Br and I. Thus, the even-odd rule becomes fully compatible with scientific knowledge of compounds in liquid or gaseous phase.
Panagis G. Papadopoulos, Christopher G. Koutitas, Yannis N. Dimitropoulos, Elias C. Aifantis
Open Journal of Physical Chemistry, Volume 7, pp 50-71; doi:10.4236/ojpc.2017.72005

Abstract:
A simplified model is proposed for an easy understanding of the coarse-grained technique and for achieving a first approximation to the behavior of gases. A mole of a gas substance, within a cubic container, is represented by six particles symmetrically moving. The impacts of particles on container walls, the inter-particle collisions, as well as the volume of particles and the inter-particle attractive forces, obeying a Lennard-Jones curve, are taken into account. Thanks to the symmetry, the problem is reduced to the nonlinear dynamic analysis of a SDOF oscillator, which is numerically solved by a step-by-step time integration algorithm. Five applications of proposed model, on Carbon Dioxide, are presented: 1) Ideal gas in STP conditions. 2) Real gas in STP conditions. 3) Condensation for small molar volume. 4) Critical point. 5) Iso-kinetic energy curves and iso-therms in the critical point region. Results of the proposed model are compared with test data and results of the Van der Waals model for real gases.
Gildas K. Gbassi, Thodhekes N. S. J. Yao, Patrick G. Atheba, Mariette D. Yehe, Germain A. Brou, Michele Ake, Albert Trokourey
Open Journal of Physical Chemistry, Volume 7, pp 27-34; doi:10.4236/ojpc.2017.72003

Abstract:
Iodization of dietary salt is recommended to prevent and control iodine deficiency disorders. The kinetic study of dietary iodized salt proves to be of interest not only for the determination of the conditions of production of iodine, but also for a good knowledge of the kinetic and thermodynamic parameters of the reaction. In this work, two salt brands were studied and one of them was used for the kinetic study. The kinetic study showed that the reaction proceeded slowly at a medium rate. Since the reaction admits a global order equal to 1, potassium iodide has no influence on this reaction rate. The concentration of iodate ions introduced in the dietary salt is a kinetic parameter that affects the reaction rate. Calculated rate constant was inversely proportional to time. The study has therefore determined experimentally kinetic parameters of the reaction between iodate and iodide ions.
Francisco Casanova-Del-Angel
Open Journal of Physical Chemistry, Volume 7, pp 123-132; doi:10.4236/ojpc.2017.74008

Abstract:
Most drinkable water supplied to the public in Mexico City comes from deep wells which extract water from the subsoil. Before being distributed, it is treated in steel filtration tanks. This water must be subject to evaluation through physic-chemical and bacteriological analyses in order to determine its quality. However, doubts always remain over the influence of the components of this water on the corrosive behavior of the filtration tanks. In light of this, this article studies the physic-chemical characterization values of water and presents the results. This has also enabled the analysis of the corrosion speed of filtration tanks components, boilers and water-cooled systems, where incrustations in pipes, obstructions and loss of heat transfer efficiency occur, rendering drinkable water bad tasting and, after some time, causing pitting corrosion although this type of corrosion only causes serious problems in the long term.
Henk M. Buck
Open Journal of Physical Chemistry, Volume 7, pp 9-25; doi:10.4236/ojpc.2017.71002

Abstract:
It has been shown that the recently discovered sulfur trihydride (H3S) can be considered as a superconductor with a transition temperature Tc of 203 Kelvin (K) at 155 GigaPascals (GPa). This is the highest Tc value reported for any superconductor. The established superconductivity occurs via the formation of a molecular system with sulfur atoms arranged on a body-centered cubic lattice. It has been generally accepted that the high Tc value is the result of an efficient electron-phonon interaction. The responsible substance formed by H2S under high pressure, may be considered as a compound with H3S stoichiometry creating an impressive network with hydrogens. We will focus on the hydrogen bonding between sulfur and hydrogens demonstrating a symmetrical arrangement. The geometry of the individual radical compound in relation to corresponding systems will be discussed. Ab initio calculations based on a linear three-center two-, three- and four-electron type of bonding clearly visualized in combination with the dynamics of the Van’t Hoff concept, as described by us in various papers, give a good description of this exclusive network. We also discuss the superconductivity of related phosphorus hydrides and focus on the stability and geometrical differences with respect to the H3S system. These differences are significant, demonstrating the diversity in various structures in showing superconductivity.
Geoffroy Auvert
Open Journal of Physical Chemistry, Volume 6, pp 67-77; doi:10.4236/ojpc.2016.63007

Abstract:
Building on the recent success of the even-odd rule, the present paper explores its implications by studying the very specific case of OXO compounds. These compounds are usually represented with double bonds linking two oxygen atoms to a central atom—as in carbon dioxyde—yet can sometimes be drawn in a triangular structure, such as in calcium dioxyde. Measurement data moreover indicate that most OXO compounds have an angle around 120° between oxygen atoms, although that seems incompatible with triangular representations. The aim here is to unify these commonly admitted representations by linking oxygen atoms through a single bond that is longer than usual covalent bonds: an “elongated bond”. This elongated bond has the interesting effect of suppressing the need for double bonds between oxygen and the central atom. The elongated bond concept is applied to about a hundred of molecules and ions and methodically compared to classical representations. It is shown that this new representation, associated to the even-odd rule, is compatible with all studied compounds and can be used in place of their classical drawings. Its usage greatly simplifies complex concepts like resonance and separated charges in gases. Elongated bonds are also shown to be practicable with the isoelectronic rule as well as isomers, and throughout chemical reactions. This study of an especially long and wide angle bond confirms the versatility of the even-odd rule: it is not limited to compounds with short covalent bonds and can include OO covalent bond lengths of more than 200 pm and with OXO angles above 90°.
Sebastiano Tosto
Open Journal of Physical Chemistry, Volume 6, pp 109-128; doi:10.4236/ojpc.2016.64011

Abstract:
This article emphasizes that the Einstein and Debye models of specific heats of solids are correlated more tightly than currently acknowledged. This correlation is evidenced without need of additional hypotheses on the early Einstein model. The results are also extensible to the case of a system of fermions; as an example, the specific heat of the electron sea in metals is inferred in the frame of the proposed approach only.
, Amina Tachafine, Didier Fasquelle, Mohamed Elaatmani, Jean-Claude Carru, Abdelouahad Zegzouti, Mohamed Daoud
Open Journal of Physical Chemistry, Volume 6, pp 42-47; doi:10.4236/ojpc.2016.62004

Abstract:
This Ce-doped strontium bismuth tantalate SrBi1.8Ce0.2Ta2O9 was prepared by solid-state reaction. X-ray diffraction was used to determine the crystal structure of the powders. The Raman spectrum of SrBi1.8Ce0.2Ta2O9 sample was measured to confirm X-ray diffraction result. The microstructure of ceramic was observed by Scanning Electron Microscope (SEM). The Temperature dependence of the dielectric properties of ceramic was investigated from the room temperature to 400°C.
, Luiz Alberto Canalle, Jochum Smid, Jan Meuldijk
Open Journal of Physical Chemistry, Volume 6, pp 101-108; doi:10.4236/ojpc.2016.64010

Abstract:
Sinapinic acid is a widespread compound in vegetable material and is as such common in the human diet. Recently it has drawn attention because of its biological activities. Sinapinic acid can be synthesized from syringaldehyde via the Knoevenagel-Doebner condensation. However this reaction is limited by the formation of 4-vinylsyringol after a second decarboxylation. To gain more detailed information about this reaction and to improve control over the formation of sinapinic acid, the concentration time history of syringaldehyde and the reaction products of this reaction have been monitored over time at different reaction temperatures. The formation of 4-vinylsyringol was found to be inhibited by performing the reaction at temperature below 80°C. This allows the reaction to be optimized for the production of sinapinic acid, with an optimal yield of 78% after 2.5 hours at 70°C.
Yoshihiro Mizukami
Open Journal of Physical Chemistry, Volume 6, pp 79-85; doi:10.4236/ojpc.2016.64008

Abstract:
Photochemical reactions of microcystin-LR, a toxic compound produced by some blue green algae, were investigated. Ultraviolet absorption of microcystin-LR was assessed. Time-dependent density functional theory (TDDFT) calculations indicated that absorption peak at 238 nm was mainly due to excitation of electrons from the linear chain structure Adda of microcystin-LR. Irradiation of microcystin-LR with UV light resulted in the reduction of the 238 nm absorption peak and the appearance of a new peak at 300 nm. Density functional theory (DFT) and TDDFT calculations with a model molecule suggested that this 300 nm peak was due to tricyclo-Adda microcystin-LR, an intermediate in photochemical reactions of microcystin-LR. Analysis of the rate of this photochemical reaction showed that it was a first order reaction.
Fatma Mohamed Mahgoub, S. M. Al-Rashdi
Open Journal of Physical Chemistry, Volume 6, pp 54-66; doi:10.4236/ojpc.2016.63006

Abstract:
Corrosion inhibition of mild steel in 0.5 mol/L H2SO4 was investigated in the absence and presence of different concentrations of thiosemicarbazide. The inhibition efficiency of thiosemicarbazide was studied by electrochemical impedance methods, potentiodynamic polarization and scanning electron microscopy at different inhibitor concentrations. Inhibition efficiency, corrosion rate and surface coverage were evaluated at different concentrations of thiosemicarbazide. Electrochemical impedance plots indicated that the presence of the inhibitors increased the charge transfer resistance of the corrosion process, increasing the inhibition efficiency. Polarization curves showed that this compound acted as mixed type inhibitor. The results of the investigation showed that this compound had good inhibiting properties for mild steel corrosion in 0.5 M sulfuric acid. The adsorption isotherm studies showed that Thiosemicarbazide adsorbed chemisorbed and formed a stable surface complex on the mild steel surface. And Langmuir obeyed the adsorption isotherm. Scanning electron microscopy analysis shows that, the surface morphology of the polished mild steel in the presence of thiosemicarbazide as inhibitor is smoother surface as compared with polished mild steel specimen in the absence of inhibitor.
Open Journal of Physical Chemistry, Volume 6, pp 86-100; doi:10.4236/ojpc.2016.64009

Abstract:
It is currently admitted that the intermolecular forces implicated in Gas Liquid Chromatography (GLC) can be expressed as a product of parameters (or descriptors) of solutes and of parameters of solvents. The present study is limited to those of solutes, and among them the three ones are involved in the Van der Waals forces, whereas the two ones involved in the hydrogen bonding are left aside at this stage. These three studied parameters, which we call δ, ω and ε, respectively reflect the three types of Van der Waals forces: dispersion, orientation or polarity strictly speaking, and induction-polarizability. These parameters have been experimentally obtained in previous studies for 121 Volatile Organic Compounds (VOC) via an original Multiplicative Matrix Analysis (MMA) applied to a superabundant and accurate GLC data set. Then, also in previous studies, attempts have been made to predict these parameters via a Simplified Molecular Topology procedure (SMT). Because these last published results have been somewhat disappointing, a promising new strategy of prediction is developed and detailed in the present article.
, Souhila Boumaza, Amar Djadoun, Mohamed Trari, Ouiza Cherifi
Open Journal of Physical Chemistry, Volume 6, pp 34-41; doi:10.4236/ojpc.2016.62003

Abstract:
The steam reforming of methane over NiO/ZnO mixed oxides with different nickel contents was studied. Solids to x% Ni/ZnO (x = 4 and 10%) were deposited on ZnO by impregnation from nickel nitrate solution; after vaporization the solid is calcined at 500°C for 6 h. The catalysts were characterized by X-ray diffraction (XRD) and BET method, scanning electron microscopy (SEM) and temperature programmed reduction (TPR). The XRD patterns revealed the NiO phase for all calcined catalysts. The chemical analysis confirmed the theoretical values of nickel. The catalysts were pre-treated under hydrogen at 500°C in situ, overnight before testing for the steam reforming of methane reaction (CH4/H2O/Ar = 10/10/80) in the temperature range (475°C - 650°C) under atmospheric pressure. The activities of both catalysts were investigated in a fixed-bed reactor for the Methane Steam Reforming (MSR) reaction. Globally, it was shown that the catalyst 10% nickel content has an important effect on the catalytic performances of solids i.e. the better results of hydrogen production were obtained with 10% wt. Ni/ZnO (28 ′ 10-3 mol/g catalyst).
Page of 4
Articles per Page
by
Show export options
  Select all
Back to Top Top