Quantum-Chemical Insight Into Mechanism of Combined Intra-Intermolecular Cycloaddition

2004 ◽  
Vol 69 (1) ◽  
pp. 231-241 ◽  
Author(s):  
Petr Kulhánek ◽  
Milan Potáček ◽  
Jaroslav Koča
Keyword(s):  
Experimental Data ◽  
Reaction Mechanisms ◽  
Quantum Chemical ◽  
Activation Barrier ◽  
Probable Mechanism ◽  
Basis Set ◽  
Rate Determining Step ◽  
B3lyp Level ◽  
Opposite Sequence ◽  
Insight Into

Two different reaction mechanisms of a mixed criss-cross cycloaddition with opposite sequence of reaction steps, intra-intermolecular and inter-intramolecular, were explored by quantum-chemical calculations at the MP2 and B3LYP levels of theory and with cc-pVDZ basis set. It was found that the rate-determining step in the both mechanisms is the first step regardless of the mechanism. The Gibbs activation barrier of the intramolecular step of the intra-intermolecular sequence is by 10.4 kcal mol-1 lower than that of the intermolecular step of the inter-intramolecular sequence at the MP2 level of theory and almost the same at the B3LYP level of theory. This together with known experimental data confirms that the intra-intermolecular sequence is the most probable mechanism.

Synthesis and spectroscopic investigation of (acetylamino)pyridines

2009 ◽  
Vol 74 (9) ◽  
pp. 1295-1308 ◽  
Author(s):  
Atanas G. Chapkanov ◽  
Sonya Y. Zareva ◽  
Rositsa Nikolova ◽  
Elena Trendafilova
Keyword(s):  
Electronic Structure ◽  
Ir Spectroscopy ◽  
Condensed Phase ◽  
Quantum Chemical ◽  
The Self ◽  
Basis Set ◽  
B3lyp Level ◽  
Vibrational Characteristics ◽  
Self Association ◽  
Polarized Ir Spectroscopy

The self-association of 2- and 3-(acetylamino)pyridines in a condensed phase was investigated by conventional and linear-polarized IR spectroscopy. Interpretation of spectra of the monomer and associated forms was carried out by the reducing-difference procedure. Theoretical quantum chemical calculations at the B3LYP level of theory and with 6-31±G** basis set were performed in order to obtain the electronic structure and vibrational characteristics of both compounds.

scholarly journals Inhibition of Aluminium Corrosion in 1.0 M HCl by Caffeine: Experimental and DFT Studies

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
R. H. B. Beda ◽  
P. M. Niamien ◽  
E. B. Avo Bilé ◽  
A. Trokourey
Keyword(s):  
Experimental Data ◽  
Hydrochloric Acid ◽  
Quantum Chemical ◽  
Inhibition Efficiency ◽  
Langmuir Model ◽  
Dft Studies ◽  
Metal Dissolution ◽  
Adsorption Model ◽  
Adsorption Parameters ◽  
Insight Into

Aluminium corrosion inhibition in 1.0 M hydrochloric acid solution by caffeine has been studied using mass loss technique and quantum chemical calculations based on DFT. The inhibition efficiency was found to increase with increasing concentration of caffeine but decreases with a rise in temperature. The molecule shows the highest inhibition efficiency of 74% at 10−2 M for T=303 K. The experimental data were used to fit isotherms including Langmuir, Temkin, Freundlich, and El-Awady. The best fits were obtained with the Langmuir model and the kinetic-thermodynamic adsorption model of El-Awady. However, it was found that the adsorption parameters suit well with the isotherm of El-Awady which was chosen as the appropriate isotherm. To distinguish between physisorption and chemisorption, the Dubinin-Radushkevich adsorption model was used. The thermodynamic parameters governing the adsorption of caffeine onto aluminium and that of the metal dissolution were calculated and discussed. DFT study gave further insight into the mechanism of the inhibiting action of caffeine.

Simple theoretical models of elimination reactions on polar catalysts; Dehydration reactivity of secondary alcohols on acidic and basic catalysts

1985 ◽  
Vol 50 (4) ◽  
pp. 920-929 ◽  
Author(s):  
Jiří Sedláček
Keyword(s):  
Experimental Data ◽  
Quantum Chemical ◽  
Theoretical Models ◽  
Aliphatic Alcohols ◽  
Secondary Alcohols ◽  
Carbonium Ion ◽  
Dehydration Reactions ◽  
Aromatic Alcohols ◽  
Basic Catalysts ◽  
Simple Models

CNDO/2 calculations for simple models of adsorption and dehydration reactions of secondary aliphatic and aromatic alcohols on polar catalysts are presented. The models involve selected stages of elimination mechanisms of various types (E1, E2 and E1cB elimination). Calculated quantum chemical quantities were correlated with reported experimental data. It is shown that reactivities for the series of substituted phenylethanols correlate very well with the ease of carbonium ion formation. In the case of aliphatic alcohols, calculated quantities correlate generally with the reactivities on SiO2 and are in anticorrelation with the reactivities on Al2O3.NaOH.

Study of potential curves by UHF type methods. CH4 molecule and its dissociation products

1986 ◽  
Vol 51 (4) ◽  
pp. 731-737
Author(s):  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Experimental Data ◽  
Quantum Chemistry ◽  
High Energy ◽  
Basis Set ◽  
Electronic Correlation ◽  
Exact Methods ◽  
Energy Parameters ◽  
Bond Functions ◽  
The Individual ◽  
Potential Curves

Geometry and energy parameters of the individual dissociation intermediate steps of CH4 molecule, parameters of the barrier to linearity and singlet-triplet separation of the CH2 molecule have been calculated by means of the UMP method in the minimum basis set augmented with the bond functions. The results agree well with experimental data except for the geometry of CH2(1A1) and relatively high energy values of CH(2II) and CH2(1A1) where the existence of two UHF solutions indicates a necessity of description of the electronic correlation by more exact methods of quantum chemistry.

scholarly journals Mechanisms of Degradation of Toxic Nerve Agents: Quantum-chemical Insight into Interactions of Sarin and Soman with Molybdenum Dioxide

2020 ◽  
Vol 700 ◽  
pp. 121639 ◽  
Author(s):  
Roman Tsyshevsky ◽  
Ashley R. Head ◽  
Lena Trotochaud ◽  
Hendrik Bluhm ◽  
Maija M. Kuklja
Keyword(s):  
Quantum Chemical ◽  
Nerve Agents ◽  
Molybdenum Dioxide ◽  
Insight Into

scholarly journals Crystal structure of a new monoclinic polymorph ofN-(4-methylphenyl)-3-nitropyridin-2-amine

2014 ◽  
Vol 70 (8) ◽  
pp. 58-61
Author(s):  
Aina Mardia Akhmad Aznan ◽  
Zanariah Abdullah ◽  
Vannajan Sanghiran Lee ◽  
Edward R. T. Tiekink
Keyword(s):  
Three Dimensional ◽  
Basis Set ◽  
Dihedral Angles ◽  
Asymmetric Unit ◽  
Acta Cryst ◽  
Common Features ◽  
Compound C ◽  
B3lyp Level ◽  
The Common ◽  
Independent Molecules

The title compound, C12H11N3O2, is a second monoclinic polymorph (P21, withZ′ = 4) of the previously reported monoclinic (P21/c, withZ′ = 2) form [Akhmad Aznanet al.(2010).Acta Cryst.E66, o2400]. Four independent molecules comprise the asymmetric unit, which have the common features of asyndisposition of the pyridine N atom and the toluene ring, and an intramolecular amine–nitro N—H...O hydrogen bond. The differences between molecules relate to the dihedral angles between the rings which range from 2.92 (19) to 26.24 (19)°. The geometry-optimized structure [B3LYP level of theory and 6–311 g+(d,p) basis set] has the same features except that the entire molecule is planar. In the crystal, the three-dimensional architecture is consolidated by a combination of C—H...O, C—H...π, nitro-N—O...π and π–π interactions [inter-centroid distances = 3.649 (2)–3.916 (2) Å].

F-CENTER IMPACT ON PHOTOELECTROCHEMICAL PROPERTIES IN HEMATITE

2010 ◽  
Vol 24 (18) ◽  
pp. 1963-1970 ◽  
Author(s):  
ARVIDS STASHANS ◽  
RICHARD RIVERA
Keyword(s):  
Experimental Data ◽  
Optical Properties ◽  
Oxygen Vacancy ◽  
Quantum Chemical ◽  
Vacancy Defect ◽  
Chemical Model ◽  
Photoelectrochemical Properties ◽  
Structural And Optical Properties ◽  
F Center ◽  
Quantum Chemical Model

Structural and optical properties of F-center (two electrons trapped by an oxygen vacancy) defect in hematite have been studied using a quantum-chemical model. Calculated absorption energies, 0.9 eV and 3.6 eV, are discussed in terms of the available experimental data. An explanation for the origin of experimentally observed electron depletion in hematite is proposed.

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