Gas-phase reaction of ClO− with CHnCl4-n (n = 0, 1, 2, 3) and CX3H (X = F, Cl and Br): Substituent effect from a comparative study

Substituent effects on reactivity are studied using the hybrid B3LYP and BHandHLYP methods of density functional theory with the aug-cc-pVDZ basis set. The chosen testing models includes two very representative reactions in chemical research, the bimolecular nucleophilic substitution (SN2) reaction and the deprotonation reaction, in which the former is represented by ClO− + CHnCl4-n (n = 0, 1, 2, 3), and the latter is based on reactions of ClO− with CX3H (X = F, Cl, and Br). Our theoretical findings suggest that a heavier substituent X in substrate results in a higher activation energy, a slower SN2 reaction, but a faster deprotonation reaction. Those are well confirmed by some presented results from bond orders, second-order perturbative energy E(2), and activation strain model analysis. Moreover, we have further explored the reactivity difference derived from substituent effects in term of the relationships of reactive barrier with the charges transferred and the leaving-bond distance in TSs, respectively, especially the TSs in SN2 reactions. Again, the rate constants at 298–1000 K are also evaluated for the SN2 reactions presented through the transition state theory.

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Quantum Mechanical Predictions of the Antioxidant Capability of Moracin C Isomers

Frontiers in Chemistry ◽

10.3389/fchem.2021.666647 ◽

2021 ◽

Vol 9 ◽

Author(s):

Angela Parise ◽

Bruna Clara De Simone ◽

Tiziana Marino ◽

Marirosa Toscano ◽

Nino Russo

Keyword(s):

Density Functional ◽

Transition State Theory ◽

State Theory ◽

Radical Addition ◽

Hydrogen Atom Transfer ◽

Basis Set ◽

Single Electron Transfer ◽

Functional Theory ◽

Exchange Correlation ◽

Radical Adduct

The antioxidant capability of moracin C and iso-moracin C isomers against the OOH free radical was studied by applying density functional theory (DFT) and choosing the M05-2X exchange-correlation functional coupled with the all electron basis set, 6-311++G(d,p), for computations. Different reaction mechanisms [hydrogen atom transfer (HAT), single electron transfer (SET), and radical adduct formation (RAF)] were taken into account when considering water- and lipid-like environments. Rate constants were obtained by applying the conventional transition state theory (TST). The results show that, in water, scavenging activity mainly occurs through a radical addition mechanism for both isomers, while, in the lipid-like environment, the radical addition process is favored for iso-moracin C, while, redox- and non-redox-type reactions can equally occur for moracin C. The values of pKa relative to the deprotonation paths at physiological pH were predicted in aqueous solution.

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Conversion of methane to benzene in CVI by density functional theory study

Scientific Reports ◽

10.1038/s41598-019-56136-0 ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Kun Li ◽

Hejun Li ◽

Ningning Yan ◽

Tiyuan Wang ◽

Wei Li ◽

...

Keyword(s):

Density Functional Theory ◽

Rate Constants ◽

Density Functional ◽

Reaction Pathway ◽

Chemical Species ◽

State Theory ◽

Chemical Vapor Infiltration ◽

Basis Set ◽

Functional Theory ◽

Conversion Of Methane

AbstractA density functional theory (DFT) study was employed to explore the mechanism of the conversion of methane to benzene in chemical vapor infiltration (CVI) based on the concluded reaction pathways from C1-species to C6-species. The geometry optimization and vibrational frequency analysis of all the chemical species and transition states (TS) were performed with B3LYP along with a basis set of 6–311 +G(d, p), and Gaussian 09 software was used to perform the study. The rate constants were calculated by KiSThelP according to the conventional transition state theory (TST), and the Wigner method was applied to acquire the tunneling correction factors. Then the rate constants were fitted to the modified Arrhenius expression in the temperature range of 800–2000 K. As for the barrierless reactions calculated in this paper, the rate constants were selected from the relating references. Through the energetic and kinetic calculations, the most favorable reaction pathway for benzene formation from methane was determined, which were mainly made of the unimolecular dissociation. The conversion trend from C1-species to C4-species is mainly guided by a strong tendency to dehydrogenation and the pathways from C4-species to C6-species are all presumed to be able to produce C6H6 molecule.

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Quantum calculation on night-time degradation of 2-chloroethyl ethyl ether (CH3CH2OCH2CH2Cl) initiated by NO3 radical

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633617500687 ◽

2017 ◽

Vol 16 (08) ◽

pp. 1750068 ◽

Cited By ~ 2

Author(s):

Nand Kishor Gour ◽

Plaban Jyoti Sarma ◽

Bhupesh Kumar Mishra ◽

Ramesh Chandra Deka

Keyword(s):

Ethyl Ether ◽

Density Functional ◽

Minimum Energy ◽

State Theory ◽

Basis Set ◽

Night Time ◽

Functional Theory ◽

Atmospheric Lifetime ◽

Radiative Efficiency ◽

No3 Radical

A dual-level quantum chemical calculations have been carried out on the initiation of night-time degradation of 2-chloroethyl ethyl ether (CH3CH2OCH2CH2Cl) via H-abstraction by NO3 radical. Within the scope of density functional theory, the electronic structure of all the species involved in the titled reaction has been optimized at M06-2X functional along with 6-31[Formula: see text]G(d,p) basis set. A higher level of couple cluster CCSD(T) method in conjunction with 6-311[Formula: see text]G(d,p) basis set has been used for the refined energy of the species. All minima and saddle states involved in the reaction channel have been characterized on the potential energy surface (PES). From PES, it is confirmed that H-abstraction from methylene (–CH2–) of ethyl (CH3CH2–) part of CH3CH2OCH2CH2Cl follows the minimum energy path. The rate constants (individual and overall) of the titled reaction are obtained using Canonical Transition State Theory (CTST) over the temperature range of 250–350[Formula: see text]K. The atmospheric lifetime and radiative efficiency of the titled molecule have also been estimated, amounting to 0.23 years and 0.024 years, respectively. The Global Warming Potentials of the 2-chloroethyl ethyl ether in 20 years, 100 years and 500 years time horizon were found to be 0.13, 0.04 and 0.01, respectively.

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Application of Ab Initio Quantum Mechanical Calculations to Investigate Oxidation of C-7 and C-14 Methyl Esters: An Alternative Fuel

Volume 3: Combustion Science and Engineering ◽

10.1115/imece2009-11255 ◽

2009 ◽

Author(s):

I. Shafagh ◽

K. J. Hughes ◽

M. Pourkashanian ◽

A. Williams

Keyword(s):

Density Functional ◽

Methyl Esters ◽

Carbon Number ◽

State Theory ◽

Basis Set ◽

Functional Theory ◽

Bimolecular Reactions ◽

The Density Functional Theory ◽

Complete Basis Set ◽

The One

Using Gaussian 03 [1] program the electronic structure of the C-14 methyl ester, C14H28O2 (methyl tridecanoate), one of the components of biodiesel and the species involved in the unimolecular and bimolecular decompositions of it were estimated. For the electronic calculations the density functional theory (DFT) at B3LYP/6-311G(d, p) level and complete basis set (CBS-QB3) were applied. Using the KHIMERA program [2], contributions from energies, harmonic vibrational frequencies and moments of inertia were utilized to construct modified Arrhenius rate expressions for bimolecular reactions. C7H14O2 was selected as a surrogate for the C14H28O2 fuel in order to study the bimolecular reactions with flame radicals. In the present work reactions of carbons number 5 and 6 of C7H14O2, where carbon number 1 is the one single bonded to oxygen atom, with flame reactive radicals such as CH3, HO2 and H were studied. The rate expressions for the cited reactions were estimated using transition state theory as implemented in KHIMERA, over the temperature 500–2000 K. Heat of reactions for unimolecular decompositions were also calculated and compared to those from Methyl Butanoate (MB).

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Evaluating Transition Metal Barrier Heights with the Latest DFT Exchange–Correlation Functionals – the MOBH35 Benchmark Dataset

10.26434/chemrxiv.7732262.v1 ◽

2019 ◽

Author(s):

Mark Iron ◽

Trevor Janes

Keyword(s):

Transition Metal ◽

Density Functional ◽

Computational Cost ◽

Basis Set ◽

Functional Theory ◽

Exchange Correlation ◽

Barrier Heights ◽

Complete Basis Set ◽

Complete Basis Set Limit ◽

Hybrid Functionals

A new database of transition metal reaction barrier heights – MOBH35 – is presented. Benchmark energies (forward and reverse barriers and reaction energy) are calculated using DLPNO-CCSD(T) extrapolated to the complete basis set limit using a Weizmann1-like scheme. Using these benchmark energies, the performance of a wide selection of density functional theory (DFT) exchange–correlation functionals, including the latest from the Truhlar and Head-Gordon groups, is evaluated. It was found, using the def2-TZVPP basis set, that the ωB97M-V (MAD 1.8 kcal/mol), ωB97X-V (MAD 2.1 kcal/mol) and SCAN0 (MAD 2.1 kcal/mol) hybrid functionals are recommended. The double-hybrid functionals PWPB95 (MAD 1.6 kcal/mol) and B2K-PLYP (MAD 1.8 kcal/mol) did perform slightly better but this has to be balanced by their increased computational cost.

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Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

10.26434/chemrxiv.9912860 ◽

2019 ◽

Author(s):

Kamal Batra ◽

Stefan Zahn ◽

Thomas Heine

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Large Scale ◽

Absolute Error ◽

Time Dependent ◽

Basis Set ◽

Basis Sets ◽

Functional Theory ◽

Framework Materials ◽

Dependent Density

<p>We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV). </p>

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