Fluxional behaviour of tricyclo[2.2.1.02,6]heptaphosphide trisanion: a DFT investigation

2015 ◽  
Vol 70 (12) ◽  
pp. 871-878 ◽  
Author(s):  
Meha Bhargava ◽  
Pooja Maheshwari ◽  
Manjinder Kour ◽  
Raj K. Bansal
Keyword(s):  
Energy Barrier ◽  
Density Functional ◽  
Sigmatropic Rearrangement ◽  
Valence Shell ◽  
Activation Energy Barrier ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Anionic Charge ◽  
Negative Hyperconjugation ◽  
Orbital Analysis

AbstractThe structures of the tricyclo[2.2.1.02,6]heptaphosphide trisanion, tricyclo[2.2.1.02,6]heptaphosphane triradical and their carbocyclic analogues have been investigated theoretically at the density functional theory (DFT) (B3LYP/6-31 + G*) level. The existence of negative hyperconjugation in these molecules could be established by natural bond orbital analysis. The weakening of the σ bonds combined with the possibility of the valence-shell expansion at the anionic charge carrying phosphorus atoms in the tricyclo[2.2.1.02,6]heptaphosphide trisanion induces a degenerate [2,2]sigmatropic rearrangement with a low energy barrier making all the phosphorus atoms equivalent, as detected by 31P NMR experimentally. This energy barrier is enhanced in the presence of counterions. Its carbocyclic analogue trisanion fails to undergo a [2,2]sigmatropic rearrangement due to the inability of the anionic carbon centres to expand their valence shell. The tricyclo[2.2.1.02,6]heptaphosphane triradical and its carbocyclic analogue undergo a [2,2]sigmatropic rearrangement, as valence-shell expansion at the carbon atom is not required in this case. A lower activation energy barrier for the [2,2]sigmatropic rearrangement of the tricyclo[2.2.1.02,6]heptane triradical as compared to that for its phospha-analogue can be rationalised on the basis of the higher ring strain of cyclopropane than triphosphirane.

A DFT study on the mechanism of reaction between 2, 4-diisocyanatotolune and cellulose

2016 ◽  
Vol 15 (02) ◽  
pp. 1650012 ◽  
Author(s):  
Jiping Cao ◽  
Yali Liu ◽  
Aijuan Shi ◽  
Yuan Yuan ◽  
Mingliang Wang
Keyword(s):  
Reaction Mechanisms ◽  
Energy Barrier ◽  
Density Functional ◽  
Membered Ring ◽  
Functional Theory ◽  
Mechanism Of Reaction ◽  
The Density Functional Theory ◽  
Good Accordance ◽  
Experimental Activation Energy ◽  
Ring Transition State

The reaction mechanisms between 2, 4-Diisocyanatotolune (2, 4-TDI) and cellulose have been investigated using the density functional theory at the B3LYP/6-31[Formula: see text]G (d, p) level. The calculations show that the direct addition of 2, 4-TDI and cellulose possesses an unrealistically high barrier of 32–34[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. With a neighboring [Formula: see text]-d-glucose serving as a proton transporter by forming a flexible six-membered ring transition state, the energy barrier of the reaction is significantly reduced to 16–18 kcal[Formula: see text]mol[Formula: see text], which is in a good accordance with the experimental activation energy of 13.9–16.7[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is indicated that the reaction between 2, 4-TDI and cellulose is auto-catalyzed with a neighboring [Formula: see text]-d-glucose acting as a reactive catalyst.

Computational and Experimental investigation of Nalipoite-Li2APO4 (A = Na, K) electrolytes for Li-ion batteries

2015 ◽  
Vol 1740 ◽  
Author(s):  
G. F. Ortiz ◽  
M C. López ◽  
M.E. Arroyo-de Dompablo ◽  
José L. Tirado
Keyword(s):  
Energy Barrier ◽  
Density Functional ◽  
Ionic Mobility ◽  
First Principles Calculations ◽  
Li Ion Batteries ◽  
Ionic Conductors ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Li Ion ◽  
Calculated Energy Barrier

ABSTRACTThe potential ionic conductors Li2APO4 (A = Na, K) are investigated combining experiments and first principles calculations at the Density Functional Theory level. A high ionic conductivity of 6.5 x10−6 and 1.5 x10−5 S cm−1 at 25 and 70°C, respectively, is found in Nalipoite-Li2NaPO4. For this mixed phosphate the energy barriers to Li motion are calculated. The lower energy barrier (0.7 eV) implies the inter-chain diffusion of Li in the b-c plane. We predict that ionic mobility is enhanced in the isostructural Li2KPO4, with the lowest calculated energy barrier being 0.4 eV.

FIRST-PRINCIPLES STUDY OF Ni ADSORPTION ON Mo(110)

2008 ◽  
Vol 15 (05) ◽  
pp. 661-668
Author(s):  
Y. G. ZHOU ◽  
X. T. ZU ◽  
J. L. NIE ◽  
H. Y. XIAO
Keyword(s):  
First Principles ◽  
Energy Barrier ◽  
Density Functional ◽  
Geometric Analysis ◽  
Alloy Layer ◽  
Layer By Layer ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Low Coverage ◽  
Theory Framework

The adsorption of Ni atom on the Mo (110) surface has been studied within the density functional theory framework. It turned out that Ni–Mo surface alloy was formed with Ni atoms substituting Mo atom in the outermost layer. The subsurface site adsorption was found to be not preferred. Geometric analysis showed that the rumpling between substitutional Ni and Mo in the first alloy layer was about 0.108 Å at medium and low coverage (Θ). In addition, the diffusion of Ni on bare and Ni -substitutional Mo (110) surface has been investigated. It was shown that the diffusion energy barrier was reduced as the increase of coverage on bare Mo (110) surface, which supports the switch of growth mode layer-by-layer to Stranski–Krastanov as the function of coverage. Substitutional Ni atom only slightly increases the energy barrier for Ni diffusion on Mo (110) surface.

A THEORETICAL STUDY OF UNSATURATED OLEFIN HYDROGENATION AND ISOMERIZATION ON Pd(111)

2008 ◽  
Vol 15 (03) ◽  
pp. 249-259 ◽  
Author(s):  
PATRICIA G. BELELLI ◽  
NORBERTO J. CASTELLANI
Keyword(s):  
Energy Barrier ◽  
Density Functional ◽  
Theoretical Study ◽  
High Energy ◽  
Slab Model ◽  
Functional Theory ◽  
Hydrogen Addition ◽  
High Energy Barrier ◽  
The Density Functional Theory ◽  
Cis And Trans

The addition of hydrogen to the carbon–carbon double bond of 2-butenes adsorbed on Pd (111) was studied within the density functional theory (DFT) and using a periodic slab model. For that purpose, the Horiuti–Polanyi mechanisms for both complete hydrogenation and isomerization were considered. The hydrogenation of cis and trans-2-butene to produce butane proceeds via the formation of eclipsed and staggered-2-butyl intermediates, respectively. In both cases, a relatively high energy barrier to produce the half-hydrogenated intermediate makes the first hydrogen addition the slowest step of the reaction. The competitive production of trans-2-butene from cis-2-butene requires the conversion from the eclipsed-2-butyl to the staggered-2-butyl isomer. As the corresponding energy barrier is relatively small and because the first of these isomers is less stable than the second, an easy conversion is predicted.

scholarly journals Mechanistic Insights into Selective Hydrogenation of C=C Bonds Catalyzed by CCC Cobalt Pincer Complexes: A DFT Study

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 168
Author(s):  
Zheng Zuo ◽  
Xinzheng Yang
Keyword(s):  
Energy Barrier ◽  
Density Functional ◽  
Pincer Complexes ◽  
Free Energy Barrier ◽  
Electronic Effects ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Hydrogenation Reactions ◽  
Catalytic Cycles ◽  
Hydrogenation Selectivity

The mechanistic insights into hydrogenations of hex-5-en-2-one, isoprene, and 4-vinylcyclohex-1-ene catalyzed by pincer (MesCCC)Co (Mes = bis(mesityl-benzimidazol-2-ylidene)phenyl) complexes are computationally investigated by using the density functional theory. Different from a previously proposed mechanism with a cobalt dihydrogen complex (MesCCC)Co-H2 as the catalyst, we found that its less stable dihydride isomer, (MesCCC)Co(H)2, is the real catalyst in those catalytic cycles. The generations of final products with H2 cleavages for the formations of C−H bonds are the turnover-limiting steps in all three hydrogenation reactions. We found that the hydrogenation selectivity of different C=C bonds in the same compound is dominated by the steric effects, while the hydrogenation selectivity of C=C and C=O bonds in the same compound could be primarily influenced by the electronic effects. In addition, the observed inhabition of the hydrogenation reactions by excessive addition of PPh3 could be explained by a 15.8 kcal/mol free energy barrier for the dissociation of PPh3 from the precatalyst.

THE DISSOCIATION AND ISOMERIZATION REACTIONS OF N11 ISOMERS

2003 ◽  
Vol 02 (01) ◽  
pp. 15-22
Author(s):  
QIAN SHU LI ◽  
YONG DONG LIU
Keyword(s):  
Density Functional Theory ◽  
Barrier Height ◽  
Energy Barrier ◽  
Lower Energy ◽  
Density Functional ◽  
Functional Theory ◽  
Barrier Heights ◽  
The Density Functional Theory

The dissociation and isomerization reactions of N 11 isomers, including the two structures 1 and 3 previously studied as well as the three new structures 2, 4, and 5, were investigated by the density functional theory (DFT) at the B3LYP/6-31G(d), B3LYP/6-311G(d), and B3LYP/6-311+G(3df)//B3LYP/6-311G(d) levels of theory. The results indicate that, similar to previous results on N 9 and N 10 isomers, the barrier heights for structures 1 and 2 to lose N 2 are about 10–15 kcal/mol whereas the barrier heights for structures 1–3 to lose N 3 are about 25–30 kcal/mol. Therefore, it seems that N 2 is easier to be eliminated than is N 3 from the relatively larger nitrogen isomers. In addition, for structures 1 and 3, both dissociation and isomerization can occur in the N8–N9 bond, due partly to its character in having an aromatic bond. Moreover, the isomerization is preferred compared with dissociation because of its relatively lower energy barrier height.

scholarly journals Single-Atom X/g-C3N4(X = Au1, Pd1, and Ru1) Catalysts for Acetylene Hydrochlorination: A Density Functional Theory Study

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 808 ◽  
Author(s):  
Zhou ◽  
Zhu ◽  
Kang
Keyword(s):  
Density Functional Theory ◽  
Energy Barrier ◽  
Density Functional ◽  
Single Atom ◽  
Functional Theory ◽  
Acetylene Hydrochlorination ◽  
B3lyp Method ◽  
The Density Functional Theory ◽  
Catalytic Mechanisms ◽  
Functional Dispersion

The mechanisms of the single-atom X/g-C3N4(X = Au1, Pd1, and Ru1) catalysts for the acetylene hydrochlorination reaction were systematically investigated using the density functional theory (DFT) B3LYP method. The density functional dispersion correction obtained by the DFT-D3 method was taken into account. During the reaction, C2H2 and HCl were well activated and the analysis of the adsorption energy demonstrated the adsorption performance of C2H2 is better than that of HCl. The catalytic mechanisms of the three catalysts consist of one intermediate and two transition states. Moreover, our results showed that the three single-atom catalysts improve the catalytic activity of the reaction to different degrees. The calculated energy barrier declines in the order of Pd1/g-C3N4 > Ru1/g-C3N4 > Au1/g-C3N4, and the energy barrier for the Au1/g-C3N4 catalyst was only 13.66 kcal/mol, proving that single-atom Au1/g-C3N4 may be a potential catalyst for hydrochlorination of acetylene to vinyl chloride.

scholarly journals Theoretical Studies of Some Fluoro Compounds with Silicon, Phosphorus and Sulphur and Establishment of Negative Hyperconjugation through Calculation of Charge

2008 ◽  
Vol 5 (1) ◽  
pp. 136-143
Author(s):  
P. K. Mohamed Imran ◽  
K. Subramani
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Anomeric Effect ◽  
Theoretical Studies ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Inductive Effects ◽  
Negative Hyperconjugation ◽  
Electronegative Atom ◽  
Bond Character

Hyperconjugation is an act to build π bond character into bonds that have only σ character. Negative Hyperconjugation is the flow or movements of electrons from π to σ* orbitals and more particularly from π orbital of a carbon atom to the σ* orbital of the C—X bond, where X is any electronegative atom. This effect is different from Inductive effects. An attempt is made to study the negative hyperconjugation (Anomeric Effect) by the calculation of the charges at the Density Functional Theory (DFT) level for some compounds with hypervalent atoms like Si, P & S

THE HYDROLYTIC DEAMINATION MECHANISM OF PROTONATED ADENINE: A DFT STUDY

2011 ◽  
Vol 10 (03) ◽  
pp. 309-320 ◽  
Author(s):  
XINLIN LIU ◽  
HUI ZENG ◽  
FANCUI MENG ◽  
JUNXIANG LIU
Keyword(s):  
Energy Barrier ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Density Functional Theory Method ◽  
Hydroxyl Group ◽  
Free Energy Barrier ◽  
Activation Energy Barrier ◽  
Functional Theory ◽  
Activation Free Energy ◽  
Hydrolytic Deamination

The hydrolytic deamination mechanism of protonated adenine has been studied using density functional theory method. There are five pathways according to adenine protonated at N1, N3 and N7, respectively. As for the N1 protonated adenine only one pathway has been found, while for N3 and N7 protonated adenine two pathways have been found. Pathway c2 is preferred due to lowest activation free energy barrier of 53.02 kcal/mol. In this pathway, the hydroxyl group of water attacks C6 atom and hydrogen atom attacks N10 atom to produce enol form of protonated hypoxanthine and ammonia, then hydrogen transfer occurs to cause enol-keto tautomerization of protonated hypoxanthine with the assistance of ammonia. Adenine deamination is easier to take place under acidic condition than under neutral condition owing to lower activation energy barrier.

High ozone chemisorption by using metal–cluster complexes: a DFT study on the nickel-decorated B12P12 nanoclusters

2017 ◽  
Vol 95 (8) ◽  
pp. 845-850 ◽  
Author(s):  
Ali Shokuhi Rad
Keyword(s):  
Adsorption Energy ◽  
Electronic Structures ◽  
Density Functional ◽  
Metal Cluster ◽  
Bond Distance ◽  
Frontier Orbital ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Charge Analysis ◽  
Orbital Analysis

In the present study, by using first-principle study within the density functional theory (DFT), we investigated the ozone (O3) chemisorption on the surface of pristine and nickel-decorated B12P12 nanoclusters. The important emphasis of this study is to follow changes in the electronic structures of the aforementioned nanoclusters upon adsorption of the O3 molecule. Although we found strong chemisorption of O3 on a pristine nanocluster (–282.7 kJ/mol), significant increases in adsorption were found by modifying the nanocluster’s surface. Firstly, we found there are three possible sites on the surface of the nanocluster for nickel (Ni) decoration. For each Ni-decorated nanocluster, we searched its potential for adsorption of O3 by using quantum chemical calculations. Depending on the location of decorated Ni, we found considerable increased values of O3 adsorption energy (–340.8, –376.8, and –382.4 kJ/mol). We carried out calculations by taking into account the values of adsorption energy, bond distance, dipole moment study, charge analysis, frontier orbital analysis, and density of states of all relaxed systems.

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