Computational Study on the Kinetics and Mechanisms of Unimolecular Reactions of (Z)-(Z)-N-(λ5-phosphanylidene) Formohydrazonic Formic Anhydride: Intramolecular aza-Wittig Reaction in Competition with Mumm Rearrangement

2020 ◽  
Vol 17 (11) ◽  
pp. 884-889
Author(s):  
Somayeh Mirdoraghi ◽  
Hamed Douroudgari ◽  
Farideh Piri ◽  
Morteza Vahedpour
Keyword(s):  
Rate Constants ◽  
Density Functional ◽  
Wittig Reaction ◽  
Computational Study ◽  
Single Step ◽  
Low Energy ◽  
Coupled Cluster ◽  
Unimolecular Reaction ◽  
Single Step Reaction ◽  
Good Agreement

For (Z)-(Z)-N-(λ5-phosphanylidene) formohydrazonic formic anhydride, Aza-Wittig reaction and Mumm rearrangement are studied using both density functional and coupled cluster theories. For this purpose, two different products starting from one substrate are considered that are competing with each other. The obtained products, P1 and P2, are thermodynamically favorable. The product of the aza-Wittig reaction, P1, is more stable than the product of Mumm rearrangement (P2). For the mentioned products, just one reliable pathway is separately proposed based on unimolecular reaction. Therefore, the rate constants based on RRKM theory in 300-600 K temperature range are calculated. Results show that the P1 generation pathway is a suitable path due to low energy barriers than the path P2. The first path has three steps with three transition states, TS1, TS2, and TS3. The P2 production path is a single-step reaction. In CCSD level, the computed barrier energies are 14.55, 2.196, and 10.67 kcal/mol for Aza-Wittig reaction and 42.41 kcal/mol for Mumm rearrangement in comparison with the corresponding complexes or reactants. For final products, the results of the computational study are in a good agreement with experimental predictions.

scholarly journals A computational study for the reaction mechanism of metal-free cyanomethylation of aryl alkynoates with acetonitrile

RSC Advances ◽  
2021 ◽  
Vol 11 (30) ◽  
pp. 18246-18251
Author(s):  
Selçuk Eşsiz
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Computational Study ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Metal Free ◽  
Coupled Cluster Methods ◽  
High Level ◽  
Cluster Methods

A computational study of metal-free cyanomethylation and cyclization of aryl alkynoates with acetonitrile is carried out employing density functional theory and high-level coupled-cluster methods, such as [CCSD(T)].

scholarly journals A computational study of the fluctional behaviour of group 14 substituted ortho-semiquinone radicals

2011 ◽  
Vol 89 (2) ◽  
pp. 235-240 ◽  
Author(s):  
K. U. Ingold ◽  
Gino A. DiLabio
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Rate Constant ◽  
Density Functional ◽  
Computational Study ◽  
Group 14 ◽  
Functional Theory ◽  
Semiquinone Radicals ◽  
Experimental Values ◽  
Good Agreement

The dynamics of the 1,4-migration of some O-substituted 3,5-di-tert-butyl-ortho-semiquinone radicals have been calculated by density-functional theory (DFT). There is very good agreement in the rate constant and Arrhenius parameters between these calculations and experimental values for migration of H, D, and the Me3Si group. For the Me3Sn group, the calculations indicate an incredibly fast migration (k293K = 2.0 × 1012 s–1), a result that is consistent with experimental data (k293K > 109 s–1). Other O-substituents examined by DFT and compared with experimental data were H3C and Me2ClSn.

Static second hyperpolarizability of twisted ethylene: A comprehensive computational study

2015 ◽  
Vol 14 (08) ◽  
pp. 1550060 ◽  
Author(s):  
Avijit Mondal ◽  
Kaushik Hatua ◽  
Prasanta K. Nandi
Keyword(s):  
Electron Correlation ◽  
Density Functional ◽  
Computational Study ◽  
Present Calculation ◽  
Functional Theory ◽  
Second Hyperpolarizability ◽  
Dominant Feature ◽  
Diradical Character ◽  
Static Electron ◽  
Good Agreement

Twisted conformations of ethylene molecule have diradical character and the second hyperpolarizability of these conformations is best described by the multiconfigurational self consistence field theory (MCSCF) wave function. Present calculation indicates that unrestricted density functional theory (UDFT) predicts second hyperpolarizability which is qualitatively correct for the intermediate diradical region. However, for the two extremities, i.e. rear diradical region and near diradical region, the second hyperpolarizability obtained by UDFT methods differ significantly from the MRCISD result. The BHHLYP and LC-BLYP ([Formula: see text]) results of [Formula: see text] are found to be in good agreement with the MRCISD result. Using the spin-projected UDFT methods almost similar results are obtained. The reasonably fair agreement between the calculated results of second hyperpolarizability obtained at the MRCISD and CASSCF(4,4) levels demonstrates that static electron correlation is the dominant feature of twisted ethylene.

Computational study on the mechanism of the three-component reaction of dimethylacetylene dicarboxylate and triphenylphosphine with 2-acetylbutyrolactone

2015 ◽  
Vol 93 (6) ◽  
pp. 666-672 ◽  
Author(s):  
Mina Haghdadi ◽  
Sakineh Asghari ◽  
Samaneh Ramezani
Keyword(s):  
Density Functional ◽  
Wittig Reaction ◽  
Computational Study ◽  
Density Functional Theory Method ◽  
Functional Theory ◽  
Phosphorus Ylide ◽  
Intramolecular Wittig Reaction ◽  
Ring Opening Reaction ◽  
The Density Functional Theory ◽  
Three Component Reaction

The molecular mechanism of the three-component reaction of triphenylphosphine, dialkyl acetylene dicarboxylate, and 2-acetylbutyrolactone to synthesize the stabilized phosphorus ylide and 1,3-butadiene derivative via the intramolecular Wittig reaction has been investigated using the density functional theory method at the B3LYP/6-31G level of theory. Two possible reaction pathways have been characterized in detail to form the cyclobutene intermediate and in the next step; the cyclobutene intermediate undergoes the conrotatory ring-opening reaction to produce the 1,3-butadiene derivative along two possible pathways. The calculated results indicate that two pathways (pathways II and II-a) are the most energy favorable among all of the pathways, so they occur more than do the others. Moreover, the phosphorus ylide is more stable than the corresponding 1,3-butadiene, demonstrating that the intramolecular Wittig reaction could not easily occur at room temperature, which is in agreement with the experimental results.

scholarly journals A DFT Study on the Molecular Mechanism of Additions of Electrophilic and Nucleophilic Carbenes to Non-Enolizable Cycloaliphatic Thioketones

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5562
Author(s):  
Grzegorz Mlostoń ◽  
Karolina Kula ◽  
Radomir Jasiński
Keyword(s):  
Molecular Mechanism ◽  
Sulfur Atom ◽  
Molecular Mechanisms ◽  
Computational Study ◽  
Cycloaddition Reaction ◽  
Single Step ◽  
Stepwise Mechanism ◽  
Nucleophilic Carbenes ◽  
Transient Intermediate ◽  
Single Step Reaction

The molecular mechanisms of addition of dihalocarbenes and dimethoxycarbene to thioketones derived from 2,2,4,4-tetrmethylcyclobutane-1,3-dione were examined on the basis of the DFT wb97xd/6-311g(d,p)(PCM) calculations. Obtained results demonstrated that the examined processes exhibit polar nature and in the case of electrophilic dichloro-, and dibromocarbenes are initiated by the attack of carbene species onto the sulfur atom of the C=S group. Remarkably, reactions involving more electrophilic carbenes (dichloro-, and dibromocarbene) proceeds via stepwise mechanism involving thiocarbonyl ylide as a transient intermediate. In contrast, analogous reactions with nucleophilic dimethoxycarbene occur via a single step reaction, which can be considered as the [2 + 1] cycloaddition reaction initiated by the attack onto the C=S bond. A computational study showed that difluorocarbene tends to react as a nucleophilic species and resembles rather dimethoxycarbene and not typical dihalocarbene species. Significantly higher reactivity of the thioketone unit in comparison to the ketone group, both present in 3-thioxo-2,2,4,4-tetramthylcyclobutanone molecule, was rationalized in the light of DFT computational study.

scholarly journals Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

2015 ◽  
Vol 11 ◽  
pp. 1865-1875 ◽  
Author(s):  
Biljana M Šmit ◽  
Radoslav Z Pavlović ◽  
Dejan A Milenković ◽  
Zoran S Marković
Keyword(s):  
Density Functional Theory ◽  
Double Bond ◽  
Density Functional ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Reaction Products ◽  
Dft Methods ◽  
Functional Theory ◽  
H Nmr ◽  
Good Agreement

The mechanism and selectivity of a bicyclic hydantoin formation by selenium-induced cyclization are investigated. The proposed mechanism involves the intermediates formed by an electrophilic addition of the selenium reagent on a double bond of the starting 5-alkenylhydantoin prior the cyclization. These intermediates are readily converted into the more stable cyclic seleniranium cations. A key step of the mechanism is an intramolecular cyclization which is realized through an anti-attack of the internal nucleophile, the amidic nitrogen, to the seleniranium cation yielding the intermediate imidazolinium cations. Their deprotonation is followed by the formation of the fused bicyclic reaction products. Important intermediates and key transition states are studied by using density functional theory (DFT) methods. The pathways of the reaction are investigated in detail. There are two regioselective pathways related to 5-exo and 6-endo products. Theoretical calculations and the monitoring of the cyclization reaction using 1H NMR spectroscopy are in a good agreement with the proposed mechanism and are consistent with our experimental results. The preferred pathway for formation of 5-exo products is confirmed.

The Low-Energy Unimolecular Reaction Rate Constants for the Gas Phase, Ni+-Mediated Dissociation of the C−C σ Bond in Acetone

2009 ◽  
Vol 113 (39) ◽  
pp. 10417-10424 ◽  
Author(s):  
Vanessa A. Castleberry ◽  
S. Jason Dee ◽  
Otsmar J. Villarroel ◽  
Ivanna E. Laboren ◽  
Sarah E. Frey ◽  
...  
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Reaction Rate ◽  
Low Energy ◽  
Unimolecular Reaction ◽  
Reaction Rate Constants

A computational study for the reaction mechanism of 2,2-azobis(isobutyronitrile)-initiated oxidative cleavage of the geminal alkenes

2021 ◽  
Author(s):  
Selçuk EŞSİZ ◽  
Uğur Bozkaya
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Computational Study ◽  
Oxidative Cleavage ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Coupled Cluster Methods ◽  
High Level ◽  
Cluster Methods

A computational study of 2,2-azobis(isobutyronitrile) (AIBN)-initiated aerobic oxidative cleavage of alkenes is carried out employing density functional theory (DFT) and high-level coupled-cluster methods, such as coupled-cluster singles and doubles with...

scholarly journals Base Catalyzed Intra Molecular Wittig Reaction Between [2-Ethoxy-3-(4-Substituted Phenyl)-2-Propenylidene] Triphenyl Phosphonium Bromides With Bifunctional Carbonyl Compounds

1970 ◽  
Vol 3 (1) ◽  
Author(s):  
Md. Saiful Islam ◽  
Ikuo Ueda
Keyword(s):  
Key Words ◽  
Full Text ◽  
Carbonyl Compounds ◽  
Wittig Reaction ◽  
Single Step ◽  
Phosphonium Bromide ◽  
Triphenyl Phosphonium ◽  
Single Step Reaction

5-ethoxycarbonyl-2-(alkyloraryl)-4-(alkyloraryl)-2-cylopenten-1-one and 2-ethoxycar-bonyl-5-(alkyl or aryl)-3-(alkyl or aryl)-2- cyclopenten-1-one derivatives and ethyl-6-(alkyl or aryl)-3-(alkyl or aryl)-6-oxo-2,4-hexadienoate derivatives have been prepared by a single step reaction between [2-ethoxy-3-(4-subsituted phenyl)-2-propenylidene triphenyl phosphonium bromides and bifunctional carbonyl compounds e.g glyoxal in presence of a base. The mechanism of the formation of the products is also proposed. Key words: Wittig Reaction, Triphenyl phosphonium bromide, Hexadienoate, Cyclopentanoate Dhaka Univ. J. Pharm. Sci. Vol.3(1-2) 2004 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

Investigation of CO2 and ethylethanolamine reaction kinetics in aqueous solutions using the stopped-flow technique

2013 ◽  
Vol 67 (9) ◽  
Author(s):  
Hanna Kierzkowska-Pawlak ◽  
Marta Siemieniec ◽  
Andrzej Chacuk
Keyword(s):  
Aqueous Solutions ◽  
Rate Constants ◽  
Original Method ◽  
Single Step ◽  
Stopped Flow ◽  
Third Order ◽  
Order Rate ◽  
Pseudo Second Order ◽  
Kinetics Of ◽  
Single Step Reaction

AbstractKinetics of the reaction of CO2 and ethylethanolamine (EMEA) in aqueous solutions has been studied using the stopped-flow technique with conductivity detection. Measurements were performed at 288 K, 293 K, 298 K, and 303 K. Amine concentration ranged from 10 mol m−3 to 37.5 mol m−3. The termolecular mechanism was applied to interpret the kinetic data. In this mechanism, carbamate formation occurs in a single-step reaction without the formation of a zwitterion intermediate. An original method of analyzing the experimental data was proposed allowing the derivation of pseudo second order rate constants from the measured kinetic traces. Based on these values, the third order rate constants $$\left( {k_{H_2 O} } \right)$$ of the reaction of CO2, water, and EMEA were derived and correlated by the Arrhenius equation.

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