Quantum chemical prediction of 2H-pyran vibration spectrum

Ab initio MO optimalization of the 2H-pyran molecule leads to a defined equilibrium geometry of this so far not identified heterocyclic molecule and to a physical justification of its existence. More advanced nonempirical wavefunctions and temperature corrections indicate that heterocyclic molecule I is energetically less stable than non-cyclic isomers II and III. Wavenumbers of fundamental vibrational transitions of heterocycle I and also known (2E)-2,4-pentadienal (IIIb were calculated using 3-21 G wavefunctions. The vibrational spectrum of compound I is predicted on the basis of correlation corrections.

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Quantum-chemical ab initio investigation of the vibrational spectrum of halon 1113 and its anharmonic force field: A joint experimental and computational approach

Chemical Physics ◽

10.1016/j.chemphys.2011.12.015 ◽

2012 ◽

Vol 397 ◽

pp. 55-64 ◽

Cited By ~ 18

Author(s):

Nicola Tasinato ◽

Andrea Pietropolli Charmet ◽

Paolo Stoppa ◽

Santi Giorgianni ◽

Alberto Gambi

Keyword(s):

Vibrational Spectrum ◽

Force Field ◽

Ab Initio ◽

Quantum Chemical ◽

Computational Approach ◽

Anharmonic Force

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The vibrational spectrum, barrier to internal rotation, and ab initio calculations of 2-chloropropane

Canadian Journal of Chemistry ◽

10.1139/v91-268 ◽

1991 ◽

Vol 69 (11) ◽

pp. 1845-1856 ◽

Cited By ~ 3

Author(s):

J. F. Sullivan ◽

Aiying Wang ◽

Mei-Shiow Cheng ◽

J. R. Durig

Keyword(s):

Vibrational Spectrum ◽

Ab Initio Calculations ◽

Ab Initio ◽

Internal Rotation ◽

Far Infrared ◽

Basis Sets ◽

Equilibrium Geometry ◽

Coupling Term ◽

Hartree Fock ◽

Experimental Values

The Raman spectra (3200–50 cm−1) of gaseous, liquid, and solid 2-chloropropane-d3 (isopropyl-d3 chloride), CH3(CD3)CHCl, and the infrared spectra (3200–50 cm−1) of the gas and solid have been recorded. The torsional transitions observed in the far infrared spectrum of the gaseous sample recorded at a resolution of 0.10 cm−1 between 265 and 135 cm−1 were analyzed in terms of the semirigid rotor model. An effective barrier of 1378 ± 4 cm−1 (3.94 ± 0.01 kcal/mol), cosine–cosine coupling term of 166 ± 10 cm−1 (0.47 ± 0.03 kcal/mol), and sine–sine coupling term of −173 ± 1 cm−1 (−0.49 ± 0.01 kcal/mol) were determined by fitting ten observed frequencies arising from the CH3 and CD3 torsions. The assignment of the 27 fundamentals is given and discussed. A complete equilibrium geometry, barrier to internal rotation, and vibrational frequencies have been determined by ab initio Hartree–Fock gradient calculations employing either 3-21G* or 6-31G* basis sets for both the d0 and d3 species. These calculated results are compared to the experimental values as well as to the corresponding quantities for some similar molecules. Key words: 2-chloropropane, vibrational spectrum; ab initio calculations; barrier to internal rotation.

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Evaluation of Chemotherapeutic Activity of the Selected Bases’ Analogues of Nucleic Acids Supported by ab initio Various Quantum Chemical Calculations

Current Computer - Aided Drug Design ◽

10.2174/1573409915666190206212024 ◽

2020 ◽

Vol 16 (2) ◽

pp. 93-103 ◽

Cited By ~ 2

Author(s):

Piotr Kawczak ◽

Leszek Bober ◽

Tomasz Bączek

Keyword(s):

Biological Activity ◽

Nucleic Acids ◽

Ab Initio ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Structural Parameters ◽

Principal Component ◽

Polarizable Continuum Model ◽

Activity Data ◽

Qsar Models

Background: Pharmacological and physicochemical classification of bases’ selected analogues of nucleic acids is proposed in the study. Objective: Structural parameters received by the PCM (Polarizable Continuum Model) with several types of calculation methods for the structures in vacuo and in the aquatic environment together with the huge set of extra molecular descriptors obtained by the professional software and literature values of biological activity were used to search the relationships. Methods: Principal Component Analysis (PCA) together with Factor Analysis (FA) and Multiple Linear Regressions (MLR) as the types of the chemometric approach based on semi-empirical ab initio molecular modeling studies were performed. Results: The equations with statistically significant descriptors were proposed to demonstrate both the common and differentiating characteristics of the bases' analogues of nucleic acids based on the quantum chemical calculations and biological activity data. Conclusion: The obtained QSAR models can be used for predicting and explaining the activity of studied molecules.

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Theoretical analysis of means of preventing Si–C bond cleavage during polycondensation of organosilanes to organosilicas

New Journal of Chemistry ◽

10.1039/d0nj05586g ◽

2021 ◽

Author(s):

Soichi Shirai ◽

Shinji Inagaki

Keyword(s):

Theoretical Analysis ◽

Ab Initio ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Bond Cleavage ◽

Model Compounds ◽

Analysis Of Means

Practical strategies for suppressing Si–C cleavage during the polycondensation of organosilanes were presented based on ab initio quantum chemical calculations of model compounds.

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Ab initio quantum-chemical calculations of the energies and structures of 1,2-acetylenedithiol isomers

Journal of Structural Chemistry ◽

10.1007/s10947-009-0029-8 ◽

2009 ◽

Vol 50 (2) ◽

pp. 195-200 ◽

Cited By ~ 1

Author(s):

Yu. V. Frolov ◽

A. V. Vashchenko ◽

A. G. Mal’kina ◽

B. A. Trofimov

Keyword(s):

Ab Initio ◽

Quantum Chemical Calculations ◽

Quantum Chemical

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Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

Zeitschrift für Naturforschung A ◽

10.1515/zna-1981-1121 ◽

1981 ◽

Vol 36 (11) ◽

pp. 1246-1252 ◽

Cited By ~ 45

Author(s):

Michael H. Palmer ◽

Isobel Simpson ◽

J. Ross Wheeler

Keyword(s):

Ab Initio ◽

Gas Phase ◽

Molecular Orbital ◽

Photoelectron Spectroscopy ◽

Relative Stability ◽

Photoelectron Spectra ◽

Equilibrium Geometry ◽

Molecular Orbital Calculations ◽

Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

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