scholarly journals A computational study of base-catalyzed reactions of cyclic 1,2-diones: cyclobutane-1,2-dione

2013 ◽  
Vol 9 ◽  
pp. 594-601 ◽  
Author(s):  
Nargis Sultana ◽  
Walter M F Fabian
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Free Energies ◽  
Reaction Paths ◽  
Acid Type ◽  
Benzilic Acid ◽  
Catalyzed Reactions

The reaction of cyclobutane-1,2-dione with hydroxide was studied by a variety of ab initio (MP2, SCS-MP2, CCSD(T), CEPA/1) and density functional (M06-2X) methods. Three possible reaction paths of the initially formed tetrahedral adduct leading to either 1-hydroxycyclopropane-1-carboxylate (benzilic acid type rearrangement, path A), α-oxobutanoate (path B) or γ-oxobutanoate (path C) were considered. Although the latter two products show similar or even more negative Gibbs free energies of reaction than calculated for the benzilic acid type rearrangement, the Gibbs free energies of activation are substantially higher. According to the calculations, the only feasible reaction appears to be the formation of 1-hydroxycyclopropane-1-carboxylate, which is corroborated by previous experimental observations.

scholarly journals Density Functional Theory and Complete Basis Set Ab Initio Computational Study of Five-, Six-, Seven- and Eight-hydrogen Coordinated Carbon Cations

1999 ◽  
Vol 23 (8) ◽  
pp. 502-503
Author(s):  
Branko S. Jursic
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Basis Set ◽  
Functional Theory ◽  
Complete Basis ◽  
Complete Basis Set ◽  
High Level

High level ab initio and density functional theory studies are performed on highly protonated methane species.

scholarly journals Computational Study of Methane C–H Activation by Main Group and Mixed Main Group–Transition Metal Complexes

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2794
Author(s):  
Carly C. Carter ◽  
Thomas R. Cundari
Keyword(s):  
Transition Metal Complexes ◽  
Active Site ◽  
Density Functional ◽  
Computational Study ◽  
Divalent Metal ◽  
Main Group ◽  
Free Energies ◽  
Functional Theory ◽  
Activation Barriers ◽  
Experimental Values

In the present density functional theory (DFT) research, nine different molecules, each with different combinations of A (triel) and E (divalent metal) elements, were reacted to effect methane C–H activation. The compounds modeled herein incorporated the triels A = B, Al, or Ga and the divalent metals E = Be, Mg, or Zn. The results show that changes in the divalent metal have a much bigger impact on the thermodynamics and methane activation barriers than changes in the triels. The activating molecules that contained beryllium were most likely to have the potential for activating methane, as their free energies of reaction and free energy barriers were close to reasonable experimental values (i.e., ΔG close to thermoneutral, ΔG‡ ~30 kcal/mol). In contrast, the molecules that contained larger elements such as Zn and Ga had much higher ΔG‡. The addition of various substituents to the A–E complexes did not seem to affect thermodynamics but had some effect on the kinetics when substituted closer to the active site.

A Proposed Mechanism of [closo-CB11H12]- Formation by Dichlorocarbene Insertion Into [nido-B11H14]-. A Computational Study by Density Functional Theory

2003 ◽  
Vol 68 (3) ◽  
pp. 644-662 ◽  
Author(s):  
Pawel Rempala ◽  
Josef Michl
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Functional Theory ◽  
Plausible Mechanism

A plausible mechanism is proposed for the insertion of dichlorocarbene into [nido-B11H14]- to yield [closo-CB11H12]- and is supported by the results of density functional theory and ab initio calculations.

scholarly journals Computational Study of the Stereoselectivity Profiles of the Diels-Alder Cycloaddition Reactions of Cyclopentadiene and Butadiene with Cyclopropenes

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Theoretical Models ◽  
Diels Alder ◽  
Cycloaddition Reactions ◽  
Free Energies ◽  
Differential Activation ◽  
Activation Free Energy ◽  
The Difference ◽  
First Time

The <i>endo</i> and <i>exo</i> stereoselectivities of the Diels-Alder (DA) cycloaddition reactions of 3,3-disubstituted cyclopropenes with butadiene and cyclopentadiene, the latter for the first time, were investigated by means of density functional and quantum chemical calculations for a comparison. To establish distinction between the selectivites, activation free energies were systematically estimated in the gas phase and also in solvents. The differential activation free energies clearly predict exclusive <i>endo</i> configuration of the products formed from the reaction of the unsubstituted cyclopropene with butadiene and cyclopentadiene. However, the results were found to be markedly different for the substituted cyclopropenes from available experimental selectivities. It was also discovered that butadiene and cyclopentadiene are markedly different in their respective stereospecific product yields, nevertheless the difference between the two was only a methylene group. The failure of the differential activation free energy approach to predict the experimental stereoselectivities of the DA reactions of several perhalocyclopropenes with cyclopentadiene is probably due to yet insufficient development of the various theoretical models dealing with the <i>endo</i> and <i>exo</i> DA preferences.

scholarly journals Computational Study of the Structural, Electronic and Magnetic Properties of Nanoclusters of Cu2O and CuO: Ab-Initio Approach

2020 ◽  
Vol 6 (1) ◽  
pp. 68-72
Author(s):  
T. P. Yadav ◽  
G. C. Kaphle ◽  
A. Srivastava
Keyword(s):  
Magnetic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Magnetic Moments ◽  
Minimum Energy ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Electronic And Magnetic Properties ◽  
Ab Initio Approach

The structural, electronic and magnetic properties of the nanoclusters of (Cu2O) n= 1, 2, 3 and (CuO) m = 2, 4, 6 have computationally studied. Density Functional Theory incorporated in Atomistic tool kit (ATK-DFT) calculators with exchange-correlation functional (SGGA+U) based ab-initio approach is applied for simulation and calculation of these nanoclusters. In the computational study, the nanoclusters (Cu2O)1, (Cu2O)3 , (CuO)2 and (CuO)6 show semiconducting behavior whereas (Cu2O)2 and (CuO)4 show semi-metallic behaviors. The nanoclusters (Cu2 O)1 and (Cu2O)3 show diamagnetic, (Cu2O)2 and (CuO)4 show ferromagnetic, (CuO)2 and (CuO)6 show antiferromagnetic behaviors. The magnetic moments 0.28μB and 0.03 μB are observed in the nanoclusters (Cu2O)2 and (CuO)4 while others are found to be as nonmagnetic . The total energy of nanoclusters have found to be decreasing towards total minimum energy with increasing number of atoms of copper oxides. The nanoclusters (Cu2O) n = 1, 2, 3 and (CuO) m = 2, 4, 6 are used in various applications as in the synthesis of technological materials. The analysis of the effects of bond length and binding energy with the size of nanoclsters have been presented.

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