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Theoretical study of hydrogen abstraction from dimethyl ether and methyl tert-butyl ether by hydroxyl radical

MP2/6-31G**//MP2/6-31G**, PMP2/6-31G**//MP2/6-31G**, MP4/6-311G(3df,2p)//MP2/6-31G**, PMP4/6-311G(3df,2p)//MP2/6-31G** and CCSD(T)/6-311++G**//MP2/6-31G** calculations have been used to investigate the H-abstraction reaction from CH3OCH3 (DME) whereas MP2/6-31G**//MP2/6-31G** and PMP2/6-31G**//MP2/6-31G** levels have been used to model the H-abstraction reaction from (CH3)3COCH3 (MTBE) by ˙OH. The methodology used has been proved to be adequate to reproduce the experimental geometrical parameters for the reactants and the C–H bond energies. The reaction rate constants for DME, calculated using the transition state theory reproduce the reported experimental results. The fact that H-abstraction is favored from the methoxy group of MTBE in comparison to the tert-butyl group has also been reproduced.

A DFT study of carbonyl oxide and its methyl-substituted analogues in solution

Abstract The properties of carbonyl oxide, syn-methylcarbonyl oxide, anti-methylcarbonyl oxide and dimethylcarbonyl oxide have been examined in the gas phase and in solution with B3LYP/6-31+G(d,p). The solution effects have been modeled with the SCIPCM method. Our findings confirm the fact that the dipolar character of carbonyl oxides increases with the number of methyl groups. The ionic configuration of the compounds studied is found to be stabilized in a polar medium resulting in a weakened OO bond and an increased double-bond character in the CO bond. Syn-methylcarbonyl oxide is found to be more stable than anti-methylcarbonyl oxide in both media.

How does the OH group affect the conversion of carbonyl oxide to dioxirane

The effects of the hydroxy group on the conversion of carbonyl oxide to dioxirane have been examined in the gas phase and in solution with B3LYP/6-31G(d,p). The solvent has been modeled with the SCIPCM method. All the possible orientations of the hydroxy group (syn-in, syn-out, anti-in, anti-out) on carbonyl oxide and dioxirane (in, out) have been considered. The Si (synin) conformer of hydroxy carbonyl oxide was not located as a stationary structure, instead peroxyformic acid is formed. The isomerization barrier for So is found to be twice as large as the one for the Ao and Ai in vacuum and in a polar mediaOea 78:5U: Single point calculations with B3LYP/6-311 1 G(3df,2p)//B3LYP/6-31G(d,p) mimic the same trend. q 2000 Elsevier Science B.V. All rights reserved.

Oxygen donor potential of carbonyl oxide and dioxirane: a DFT study

Abstract The oxygen donor potentials of carbonyl oxide and dioxirane have been examined in the gas phase B3LYP/6-31G(d, p) for their reactions with ethylene, propene, cis -2-butene, trans -2-butene and 1-cyano-ethylene. Our results have shown that the electronic and structural characteristics of the substituents alter the activation barriers. The effect of the solvent has been modeled with the SCIPCM method for ethylene. The energy barriers for the reactions of carbonyl oxide and dioxirane with ethylene have not altered in solution even though drastic changes in the electronic behavior of carbonyl oxide have been determined. An improved solvent model where specific interactions will be taken into account is suggested for further studies.

Conformational analysis of 2-substituted-l,3-diheteroanes. A theoretical study of solvent effects

Abstract Semiempirical molecular orbital calculations in the gas phase and in solution have been carried out to study the conformational equilibria of 2-substituted-l,3-dioxanes with substituents Y = - OCH 3 , - C 6 H 5 , - p - C 6 H 4 Cl and 2-substituted-l,3-dithianes with substituents Y = -CO 2 H, -CO 2 CH 3 , -SCH 3 , -OCH 3 , -SC 6 H 5 , -COC 6 H 5 . The influence of the solvent has been studied with a self-consistent reaction field (SCRF) continuum model. The effects of steric and electrostatic interactions on the axial/equatorial preference have been investigated. The entropie contributions to the free energy change have been evaluated for two model compounds. The present results are compared with the available experimental data.

Shell-like Features and Charge Localization in Protonated Helium Clusters: a Density Functional Study

The structural behaviour of ionic helium clusters which are formed by the addition of an H+ to a varying number n of He atoms is examined by considering their overall electronic stability as n is increased.

Conformational behavior of 2-dimethylamino-1,3-dithiane in solution

Ab initio molecular orbital calculations in the gas phase and in chloroform have been carried out to study the conformational equilibrium of 2-dimethylamino-1,3-dithiane. Full optimizations at the HF/6-31G, HF/6-31G* levels and single point calculations at the MP2/6-31G* level have been performed. The influence of the solvent has been studied with a self-consistent reaction field (SCRF) continuum model. The effects of steric and electrostatic interactions on the axial–equatorial preference have been investigated. The present results have been compared with the available experimental data.