A theoretical study of the nitration of eugenol with the nitronium ion

2011 ◽  
Vol 76 (12) ◽  
pp. 1529-1548
Author(s):  
Ricardo Ugarte ◽  
Guillermo Salgado ◽  
Luis Basáez
Keyword(s):  
Carbon Atom ◽  
Gas Phase ◽  
Density Functional ◽  
Molecular Electrostatic Potential ◽  
Reaction Pathway ◽  
Minimum Energy ◽  
Stationary Points ◽  
Functional Theory ◽  
Π Complex ◽  
Ring Carbon Atom

The nitration of eugenol was investigated by using density functional theory (DFT) calculations. Potential energy surface and molecular electrostatic potential of eugenol was constructed in order to find, respectively, the minimum energy conformers and the possible sites for electrophilic attack. Stationary points were located and characterized at the B3LYP/6-311++G(2d,2p) level of theory. A strongly bound π-complex was found, in which the distance between the nitrogen atom of the NO2 moiety and the C1 carbon atom of the aromatic ring is 2.15 Å in the gas phase and 2.06 Å in dichloromethane. The most favorable σ-complex or Wheland intermediate is the result from the interaction between the nitrogen and the C6 ring carbon atom. The transition state that connects both complexes is more resembling the σ-complex. The nitronium ion exothermically reacts with eugenol to give the π-complex without an energy barrier. The next stage of the reaction pathway, π-complex → σ-complex, is endothermic and involves a Gibbs energy of activation of 7.9–8.0 kcal mol–1 (gas phase) and 8.3–8.9 kcal mol–1 (CH2Cl2).

Graph theory-based reaction pathway searches and DFT calculations for the mechanism studies of free radical-initiated peptide sequencing mass spectrometry (FRIPS MS): a model gas-phase reaction of GGR tri-peptide

2020 ◽  
Vol 22 (9) ◽  
pp. 5057-5069 ◽  
Author(s):  
Jae-ung Lee ◽  
Yeonjoon Kim ◽  
Woo Youn Kim ◽  
Han Bin Oh
Keyword(s):  
Graph Theory ◽  
Dft Calculations ◽  
Gas Phase ◽  
Density Functional ◽  
Reaction Pathway ◽  
Peptide Sequencing ◽  
Phase Reaction ◽  
Functional Theory ◽  
Fragmentation Mechanisms ◽  
Gas Phase Fragmentation

A new approach for elucidating gas-phase fragmentation mechanisms is proposed: graph theory-based reaction pathway searches (ACE-Reaction program) and density functional theory (DFT) calculations.

scholarly journals Theoretical Investigation of the Hydrolytic Mechanism of α-Functionalized Alkoxysilanes as Effective Crosslinkers and the Difficulty of Deep Vulcanization in RTV Silicone Rubber

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1526
Author(s):  
Huihui Xu ◽  
Yanhong Gao ◽  
Zihou Liu ◽  
Yiling Bei
Keyword(s):  
Density Functional Theory ◽  
Silicone Rubber ◽  
Density Functional ◽  
Room Temperature ◽  
Reaction Pathway ◽  
Stationary Points ◽  
Functional Theory ◽  
Hydrolytic Mechanism ◽  
Hydrolysis Activity ◽  
Rtv Silicone Rubber

The reactions between α-, γ-ethylenediaminemethyl trimethyl-ketoxime silane (α-, γ-EAMOS) and H2O were investigated on the geometries of stationary points, the reaction pathway (IRC), thermodynamic and kinetic analysis by density functional theory (DFT) at the B3LYP/6-311G (d, p) level. Interestingly, the results showed that the hydrolysis activity of α-EAMOS is higher than that of γ-EAMOS, due to the influence of an amino substituent in position α-C on silicon. α-EAMOS can be used as a superior crosslinker for room temperature vulcanized (RTV) silicone rubber to achieve rapid crosslinking without a toxic catalyst. Besides, compared with the reaction between α-EAMOS and H2O, the reactivity between α-EAMOS and hydroxy siloxane (HO–Si(CH3)2–OSiH3) was discussed. Particularly, it revealed that the deep vulcanization of RTV silicone rubber is difficult.

scholarly journals The structure of the anti-aging agent J147 used for treating Alzheimer's disease

2019 ◽  
Vol 75 (3) ◽  
pp. 271-276 ◽  
Author(s):  
Guy J. Clarkson ◽  
M. Ángeles Farrán ◽  
Rosa M. Claramunt ◽  
Ibon Alkorta ◽  
José Elguero
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Gas Phase ◽  
Spectroscopic Data ◽  
Density Functional ◽  
Atomic Orbital ◽  
Minimum Energy ◽  
Chloroform Solution ◽  
Functional Theory ◽  
Minimum Energy Conformation

The molecular structure of the anti-aging agent J147 [systematic name: (E)-N-(2,4-dimethylphenyl)-2,2,2-trifluoro-N′-(3-methoxybenzylidene)acetohydrazide], C18H17F3N2O2, has been determined at 150 K. The crystal structure corresponds to the minimum-energy conformation in the gas phase calculated by density functional theory (DFT). 15 other conformations have been calculated and compared with the minimum, denoted 1111. NMR spectroscopic data have been obtained and compared with those from Gauge Independent Atomic Orbital (GIAO) calculations. DFT calculations allow the reduction of the 16 possible rotamers to the four most stable (i.e. 1111, 1112, 1121 and 1222); in addition, the calculated barriers connecting these minima are low enough to permit their interconversion. Comparison of the NMR spectroscopic results, both experimental and calculated, point to the 1121 isomer being present in chloroform solution.

scholarly journals Theoretical Study of the [4+2] Cycloaddition Reaction of Trifluoroethylene with Five-membered Chalcogens Heterocyclic Compounds

2019 ◽  
Vol 7 (2) ◽  
pp. 69-77
Author(s):  
Haydar A. Mohammad-Salim ◽  
Hassan H. Abdallah
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Theoretical Study ◽  
Cycloaddition Reaction ◽  
Branching Ratio ◽  
Basis Set ◽  
Stationary Points ◽  
Functional Theory ◽  
Highest Occupied Molecular Orbital ◽  
Synthesis Reactions

[4+2] cycloaddition reaction has enormous significant in organic chemistry synthesis reactions and yet remains unexplored for the synthesis of fluorine-containing compounds. A density functional theory study of the stereo- and regioselectivity of the [4+2] cycloaddition reaction of trifluoroethylene with furan, thiophene, and selenophene was carried out in the gas phase. The B3LYP functional is used throughout in combination with 6-31G(d) basis set. The analysis of stationary points and the energetic parameters indicates that the reaction mechanism is concerted and confirms that the exo-adducts are thermodynamically and kinetically more favored than endo-adducts. The calculated branching ratio indicates that the exo-adducts have the higher percent yield than endoadducts and the yield of endo-adducts is increased only slightly on proceeding from furan, through thiophene, and onto selenophene. The analysis of the frontier molecular highest occupied molecular orbital (MO) and lowest unoccupied MO orbitals indicates that the exo-adducts are more stable due to their higher energy gab. The reaction energies were compared to the MP2/6-31G(d) and CCSD(T)/6-31G(d) calculations.

THEORETICAL STUDY ON THE H2 ACTIVATION BY PtO+ AND ${\rm PtO}_{2}^{+}$ IN THE GAS PHASE

2010 ◽  
Vol 09 (06) ◽  
pp. 963-974 ◽  
Author(s):  
YONGCHUN TONG ◽  
QINGYUN WANG ◽  
DONGQING WU ◽  
YONGCHENG WANG
Keyword(s):  
Potential Energy ◽  
Gas Phase ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Reaction Pathway ◽  
Minimum Energy ◽  
Basis Sets ◽  
Avoided Crossing ◽  
Pass Through ◽  
Energy Surfaces

Gas-phase H2 activation by PtO+ and [Formula: see text] were studied at the density functional level of theory (DFT) using the relativistic effective core potential (RECP) of Stuttgart basis sets on platinum atom and UB3LYP/6-311+G(2d,2p) level on hydrogen and oxygen atoms. Two reaction profiles corresponding to the doublet and quartet multiplicities were investigated in order to ascertain the presence of some spin inversion during the H2 reduction. The electron-transfer reactivity of the reactions were analyzed using the two-state model, and the strongly crossing behavior on the transition state (TS) area were shown. Finally, the actions of frontier molecular orbitals in minimum-energy crossing point (MECP) have been illuminated briefly. These theoretical results can act as a guide to further theoretical and experimental research. H2 activation mediated by metal oxide cations were found to be an exothermic spin-forbidden process resulting from a crossing between quartet and doublet profiles. To evaluate the spin-forbidden process in the reaction pathway, the spin-obit coupling (SOC) matrix elements are calculated at the MECP with the different potential energy surfaces (PESs) and the probability of crossing between the adiabatic potential-energy surfaces during a single pass through the avoided crossing region was described. Therefore, the intersystem crossing (ISC) at crossing points (CP) occur efficiently because of the large SOC (ca. 85.58 cm-1) involved.

Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

2019 ◽  
Author(s):  
Drew P. Harding ◽  
Laura J. Kingsley ◽  
Glen Spraggon ◽  
Steven Wheeler
Keyword(s):  
Gas Phase ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Molecular Descriptors ◽  
Stacking Interactions ◽  
Interaction Energies ◽  
Functional Theory ◽  
Binding Partner ◽  
Heavy Atoms ◽  
Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

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