Comparison of an intramolecular Michael-type addition with its intermolecular counterpart: an abinitio theoretical study

Abinitio theoretical calculations were carried out on the intramolecular addition of 3-ketopent-4-en-1-olate 1 to form 1-oxacyclohex-3-en-4-olate 2 (reaction I; Scheme 1) and the corresponding intermolecular Michael addition of methanolate to butenone forming 4-methoxybut-2-en-2-olate 4 (reaction II; Scheme 1). The calculations were carried out at the RHF level using an augmented 4-31G basis set; single point energies were then taken using the 6-31 + G* basis set. The overall energy change of the reaction in going from reactants to products is very similar for both reactions, with products being about 8.3 kcal/mol more stable than reactants; the major difference energetically between the two reactions is at the level of the transition state: the transition state energy for reaction I (intramolecular) is 6 kcal/mol higher than that for reaction II (intermolecular). The transition state geometry of reaction II conforms quite closely to the stereoelectronic requirements for a Michael addition, but that of reaction I is very distorted, reflecting significant compromises in the stereoelectronic requirements. Keywords: abinitio theoretical study, Michael-type addition, intramolecular, transition state.

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Experimental and Theoretical Study of the Enthalpy of Formation of 3,6-Diphenyl-1,2,4,5-Tetroxane Molecule

The Scientific World JOURNAL ◽

10.1100/tsw.2002.126 ◽

2002 ◽

Vol 2 ◽

pp. 455-460 ◽

Cited By ~ 4

Author(s):

N.L. Jorge ◽

L.C.A. Leiva ◽

M.G. Castellanos ◽

M.E. Gomez Vara ◽

L.F.R. Cafferata ◽

...

Keyword(s):

Vapor Pressure ◽

Enthalpy Of Formation ◽

Vapor Phase ◽

Theoretical Study ◽

Theoretical Calculations ◽

Basis Set ◽

Sublimation Enthalpy ◽

Combustion Heat ◽

Different Temperatures ◽

The Enthalpy Of Formation

We report the results obtained for the experimental determination and the theoretical calculation of the enthalpy of formation of 3,6-diphenyl-1,2,4,5-tetroxane molecule. The experimental work was performed using a macrocalorimeter to measure the combustion heat, and the sublimation enthalpy was determined via the measurement of the vapor pressure at equilibrium with the vapor phase at different temperatures resorting to the Clapeyron-Claussius equation. Theoretical calculations were performed using semiempirical AM1 and PM3 methods as well asab initiotechniques at the 3-21, 6-31G(d,p), and 6-311G(d,p) basis set levels.

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A theoretical study of silyl anions and radicals. Change of mechanism from vertex inversion to edge inversion with increasing substitution by halogens

Canadian Journal of Chemistry ◽

10.1139/v90-202 ◽

1990 ◽

Vol 68 (8) ◽

pp. 1309-1316 ◽

Cited By ~ 12

Author(s):

A. C. Hopkinson ◽

C. F. Rodriquez ◽

M. H. Lien

Keyword(s):

Theoretical Study ◽

Single Point ◽

Lone Pair ◽

Basis Set ◽

Transition Structure ◽

Silyl Radicals ◽

Inversion Mechanism

Structures for trivalent silyl anions [Formula: see text] and [Formula: see text], where n takes values from 0 to 3, have been optimized at the HF/6-31 + +G* level and single point calculations made at the MP2/6-31 + +G* level (core included). SiH3− and ions containing one halogen invert by the vertex mechanism in which the lone-pair has π-symmetry, and the monosubstituted ions have high barriers (SiH2F− 45.2 kcal/mol and SiH2Cl− 44.0 kcal/mol). Further substitution by halogens results in a change to the edge inversion mechanism involving a T-shaped transition structure with the lone-pair coplanar with the ligands. Barriers (kcal/mol) at the MP2/6-31 + +G* level including ZPE are lower than for the monosubstituted ions and are SiHF2− 35.0, SiF3− 35.9, SiHCl2− 28.4, and SiCl3−32.5. In SiLi3− edge inversion is preferred, but the surface is much flatter and the barrier is low (9.8 kcal/mol). Trivalent silyl radicals SiHnF(3−n), SiHnCl(3−n) and SiFnCl(3−n) (with n having values 0 to 3) have also been examined with the 6-31 + +G* basis set, with optimization at the UHF level and single point calculations at the UMP2 level. Radicals SiH3, SiH2F, SiH2Cl, and SiHCl2 all invert by the vertex mechanism. Increased halogenation results in a change of mechanism and SiF3, SiCl3, SiF2Cl, and SiFCl2 invert by the edge mechanism. For radical SiHF2 the calculated barriers for the two mechanisms are almost identical with the higher level of theory slightly favouring edge inversion. Keywords: inversion mechanism, halogenated silyl radicals and anions.

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Ag2O versus Cu2O in the Catalytic Isomerization of Coordinated Diaminocarbenes to Formamidines: A Theoretical Study

Materials ◽

10.3390/ma15020491 ◽

2022 ◽

Vol 15 (2) ◽

pp. 491

Author(s):

Juan F. Van der Maelen ◽

Javier Ruiz

Keyword(s):

Reaction Mechanism ◽

Nitrogen Atom ◽

Carbon Atom ◽

Transition State ◽

Theoretical Study ◽

Theoretical Calculations ◽

Experimental Results ◽

Similar Reaction ◽

Isomerization Process ◽

Catalytic Isomerization

DFT theoretical calculations for the Ag2O-induced isomerization process of diaminocarbenes to formamidines, coordinated to Mn(I), have been carried out. The reaction mechanism found involves metalation of an N-H residue of the carbene ligand by the catalyst Ag2O and the formation of a key transition state showing a μ-η2:η2 coordination of the formamidinyl ligand between manganese and silver, which allows a translocation process of Mn(I) and silver(I) ions between the carbene carbon atom and the nitrogen atom, before the formation of the formamidine ligand is completed. Calculations carried out using Cu2O as a catalyst instead of Ag2O show a similar reaction mechanism that is thermodynamically possible, but highly unfavorable kinetically and very unlikely to be observed, which fully agrees with experimental results.

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A theoretical study towards thermolysis process of thionesters and thiolesters

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633618500141 ◽

2018 ◽

Vol 17 (02) ◽

pp. 1850014 ◽

Cited By ~ 3

Author(s):

Xun Zhu ◽

Xiuqin Zhou ◽

Dongsheng Xiang ◽

Ping Wu

Keyword(s):

Theoretical Study ◽

Theoretical Calculations ◽

Transition States ◽

Membered Ring ◽

Basis Set ◽

Reaction Progress ◽

Alkyl Groups ◽

Thermal Elimination ◽

Bond Indices ◽

Wiberg Bond Indices

This paper focuses on the thermal elimination of alkenes from methyl alkyl thionacetates and thiolacetates. Three alkyl groups are calculated: ethyl, isopropyl and tert-butyl. Possible elimination mechanisms are considered, including six- and four-membered ring transition states for alkene elimination, four-membered ring isomerization and a possible five-membered ring decomposition. Theoretical calculations are performed with the MP2 method and the 6-31G* basis set. Wiberg bond indices are also summarized to monitor the reaction progress.

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Cupin Variants as Macromolecular Ligand Library for Stereoselective Michael Addition of Nitroalkanes

10.26434/chemrxiv.11481834.v1 ◽

2019 ◽

Author(s):

Nobutaka Fujieda ◽

Miho Yuasa ◽

Yosuke Nishikawa ◽

Genji Kurisu ◽

Shinobu Itoh ◽

...

Keyword(s):

Michael Addition ◽

In Silico ◽

Addition Reaction ◽

Single Point ◽

Point Mutations ◽

Unsaturated Ketone ◽

Michael Addition Reaction ◽

Beta Barrel ◽

Cupin Superfamily ◽

Single Point Mutations

Cupin superfamily proteins (TM1459) work as a macromolecular ligand framework with a double-stranded beta-barrel structure ligating to a Cu ion through histidine side chains. Variegating the first coordination sphere of TM1459 revealed that H52A and H54A/H58A mutants effectively catalyzed the diastereo- and enantio-selective Michael addition reaction of nitroalkanes to an α,β-unsaturated ketone. Moreover, in silico substrate docking signified C106N and F104W single-point mutations, which inverted the diastereoselectivity of H52A and further improved the stereoselectivity of H54A/H58A, respectively.

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An NBO-TS predictive approach for torquoselectivity of ring opening in 3-substituted cyclobutenes

10.26434/chemrxiv.5743305.v1 ◽

2017 ◽

Author(s):

Arpita Yadav ◽

Dasari L V K Prasad ◽

Veejendra Yadav

Keyword(s):

Transition State ◽

Ring Opening ◽

Natural Bond Orbital ◽

Theoretical Calculations ◽

Lone Pair ◽

Product Distribution ◽

Acceptor Substituent ◽

Important Contributor ◽

Predictive Approach ◽

Donor Substituent

The torquoselectivity, the inward or outward ring opening of 3-substituted cyclobutenes, is conventionally guided by the donor and/or acceptor ability of the substituent (S). It is typically predicted by estimating the respective ring opening transition state (TS) barriers. While there is no known dissent in regard to the outward rotation of electron-rich substituents from the approaches of TS calculations, the inward rotation was predicted for some electron-accepting substituents and outward for others. To address this divergence in predicting the torquoselectivity, we have used reliable orbital descriptors through natural bond orbital theoretical calculations and demonstrated that (a) interactions nS→s*C3C4 for a lone pair containing substituent, sS→s*C3C4 for a s-donor substituent, sC3C4→p*S for a resonance-accepting substituent and sC3C4→s*S for a s-acceptor substituent constitute the true electronic controls of torquoselectivity, and (b) reversibility of the ring opening event is an additional important contributor to the observed product distribution.

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POLARON IN A QUANTUM DOT UNDER AN ELECTRIC FIELD

Modern Physics Letters B ◽

10.1142/s0217984907014012 ◽

2007 ◽

Vol 21 (24) ◽

pp. 1635-1642

Author(s):

MIAN LIU ◽

WENDONG MA ◽

ZIJUN LI

Keyword(s):

Quantum Dot ◽

Electric Field ◽

Field Intensity ◽

Ground State Energy ◽

Ground State ◽

Electric Field Intensity ◽

State Energy ◽

Theoretical Study ◽

The Moment ◽

Transformation Methods

We conducted a theoretical study on the properties of a polaron with electron-LO phonon strong-coupling in a cylindrical quantum dot under an electric field using linear combination operator and unitary transformation methods. The changing relations between the ground state energy of the polaron in the quantum dot and the electric field intensity, restricted intensity, and cylindrical height were derived. The numerical results show that the polar of the quantum dot is enlarged with increasing restricted intensity and decreasing cylindrical height, and with cylindrical height at 0 ~ 5 nm , the polar of the quantum dot is strongest. The ground state energy decreases with increasing electric field intensity, and at the moment of just adding electric field, quantum polarization is strongest.

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The SN2 reaction and its relationship with the Walden inversion, the Finkelstein and Menshutkin reactions together with theoretical calculations for the Finkelstein reaction

Structural Chemistry ◽

10.1007/s11224-021-01805-y ◽

2021 ◽

Author(s):

Ibon Alkorta ◽

José Elguero

Keyword(s):

Linear Models ◽

Theoretical Calculations ◽

Computational Method ◽

Basis Set ◽

Free Energies ◽

Nitrogen And Phosphorus ◽

Atom Pairs ◽

Leaving Groups ◽

First Time ◽

Nitrogen Phosphorus

AbstractThis communication gives an overview of the relationships between four reactions that although related were not always perceived as such: SN2, Walden, Finkelstein, and Menshutkin. Binary interactions (SN2 & Walden, SN2 & Menshutkin, SN2 & Finkelstein, Walden & Menshutkin, Walden & Finkelstein, Menshutkin & Finkelstein) were reported. Carbon, silicon, nitrogen, and phosphorus as central atoms and fluorides, chlorides, bromides, and iodides as lateral atoms were considered. Theoretical calculations provide Gibbs free energies that were analyzed with linear models to obtain the halide contributions. The M06-2x DFT computational method and the 6-311++G(d,p) basis set have been used for all atoms except for iodine where the effective core potential def2-TZVP basis set was used. Concerning the central atom pairs, carbon/silicon vs. nitrogen/phosphorus, we reported here for the first time that the effect of valence expansion was known for Si but not for P. Concerning the lateral halogen atoms, some empirical models including the interaction between F and I as entering and leaving groups explain the Gibbs free energies.

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