The relative stability of some C4H4F+ and C4H4Cl+ isomers investigated by ab initio quantum chemical methods. Are cyclic halogenophenium ions aromatic?

1986 ◽  
pp. 1857 ◽  
Author(s):  
Einar Uggerud
Keyword(s):  
Ab Initio ◽  
Relative Stability ◽  
Quantum Chemical ◽  
Chemical Methods ◽  
Quantum Chemical Methods

scholarly journals Quantum Chemical Investigation of Polychlorinated Dibenzodioxins, Dibenzofurans and Biphenyls: Relative Stability and Planarity Analysis

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5697
Author(s):  
Sopanant Datta ◽  
Taweetham Limpanuparb
Keyword(s):  
Aromatic Compounds ◽  
Relative Stability ◽  
Quantum Chemical ◽  
Prediction Models ◽  
Toxicity Prediction ◽  
Chemical Methods ◽  
Quantum Chemical Investigation ◽  
Polychlorinated Dibenzodioxins ◽  
Quantum Chemical Methods

All the possible polychlorinated aromatic compounds in the classes of dibenzodioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) were studied by the quantum chemical methods of HF/6-311++G(d,p), B3LYP/6-311++G(d,p), and MP2/cc-pVTZ. The calculated stabilities and structures of these compounds were compared with the available data on their abundance and toxicity. Prediction models for trends in energy and planarity among these congeners were proposed. The results discussed here can help contribute to the understanding of the role of dioxin-like compounds (DLCs) in the environment.

scholarly journals How accurate are approximate quantum chemical methods at modelling solute–solvent interactions in solvated clusters?

2020 ◽  
Vol 22 (7) ◽  
pp. 3855-3866 ◽  
Author(s):  
Junbo Chen ◽  
Bun Chan ◽  
Yihan Shao ◽  
Junming Ho
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Interaction Energies ◽  
Chemical Methods ◽  
Dft Methods ◽  
Solvent Interactions ◽  
Quantum Chemical Methods ◽  
Composite Methods ◽  
Wide Range

In this paper, the performance of ab initio composite methods, and a wide range of DFT methods is assessed for the calculation of interaction energies of thermal clusters of a solute in water.

Study of some aliphatic ammonium ylides by semiempirical and ab initio methods: Structure and charge distribution

1980 ◽  
Vol 45 (1) ◽  
pp. 92-103 ◽  
Author(s):  
Vladimír Král ◽  
Zdeněk Arnold
Keyword(s):  
Ab Initio ◽  
Charge Distribution ◽  
Quantum Chemical ◽  
Negative Charge ◽  
Dipole Moments ◽  
Ab Initio Methods ◽  
Chemical Methods ◽  
Quantum Chemical Methods

Structure of, and charge distribution in, some aliphatic ammonium ylides were determined by quantum chemical methods (CNDO/2, INDO, MINDO/2, PCILO, ab initio-STO-3G and 4-31G bases). Non-stabilized ylides were found to have pyramidal arrangement of bonds on the ylide carbon whereas the stabilized ylides have a planar arrangement. The charge distribution in stabilized ylides indicates a significant transfer of the negative charge from the ylide carbon to the electronegative groups. The calculated dipole moments for the previously prepared compounds, as well as for the derivatives VII and X, described in this paper, agree well with the experimental value.

scholarly journals Hydration dynamics gives the distinctive brown color in the "brown ring" nitrate test

2021 ◽  
Author(s):  
Ambar Banerjee ◽  
Michael R. Coates ◽  
Michael Odelius
Keyword(s):  
Aqueous Solution ◽  
Ab Initio ◽  
Quantum Chemical ◽  
Solution Structure ◽  
Ab Initio Molecular Dynamics ◽  
Ring Test ◽  
Chemical Methods ◽  
Aqua Complexes ◽  
Quantum Chemical Methods ◽  
Ring Complex

The brown ring test is one of the most popular and visually appealing reagent tests, commonly known to chemistry undergrads and familiar even to school students. The exact composition, mechanism and structure of the complex has been investigated for nearly a century. Recent studies have elucidated its UV-vis, EPR and Mossbauer spectra, mechanistic details and kinetics, followed by crystallization and structure determination in solid state. Nonetheless these studies were unable to address the aspects of solution structure and dynamics of the brown ring complex. We have conducted ab initio molecular dynamics simulations of the classic brown ring complex in aqueous solution. In the process from the simulation trajectory, we have identified that the classically established pseudo-octahedral [Fe(H2O)5(NO)]2+ complex is in chemical equilibrium with the square-pyramidal [Fe(H2O)4(NO)]2+ complex through the exchange of one of the coordinated H2O molecules. The dynamics in aqueous solution between the penta-aqua and tetra-aqua complexes in the brown ring system has to our knowledge never been suggested earlier. Interestingly we find, using ab initio multi-reference quantum chemical methods i.e. CASSCF/NEVPT2 and CASPT2 calculations, that the mixture of these two complexes is what gives the distinctive brown coloration to the brown ring test. We show that its UV-vis spectrum can be theoretically reproduced only by accounting these two species, and not solely the classically established [Fe(H2O)5(NO)]2+ complex. The energetics of the penta-aqua and tetra-aqua complexes is also investigated at the level of multi-reference quantum chemical methods.

Trimethylammoniodiformylmethylide: Structure and charge distribution

1980 ◽  
Vol 45 (1) ◽  
pp. 80-91 ◽  
Author(s):  
Vladimír Král ◽  
Zdeněk Arnold
Keyword(s):  
Dipole Moment ◽  
Total Energy ◽  
Ab Initio ◽  
Charge Distribution ◽  
Quantum Chemical ◽  
Energy Minimum ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Total Energy Minimum

Geometric arrangement of trimethylammoniodiformylmethylide (I) and charge distribution in this compound were calculated by quantum chemical methods (EHT, CNDO/2, INDO, PCILO, MINDO/2, ab initio). Total energy minimum was found for the arrangement If. The experimentally found dipole moment agrees very well with that calculated for this conformation.

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