The performance of the B3LYP density functional theory calculations has been studied for epoxidation reactions ethylene, propene, and cis- trans-2-butene with peroxyformic acid ethylene dioxirane dimethyldioxirane. transition structures propene dimethyldioxirane calculated at level as well QCISD CCSD levels are symmetrical nearly identical C−O bond distances, whereas MP2 favor unsymmetrical structures. geometrical parameters using close to those found levels. While activation barriers...

The potential energy surface involved in the thermal decomposition of 1-propanol radicals was investigated detail using automated codes (tsscds2018 and Q2DTor). From predicted elementary reactions, a relevant reaction network constructed to study at temperatures range 1000–2000 K. Specifically, this comprises 18 conformational channels (CRCs), which general exhibit large wealth conformers reactants transition states. Rate constants for all CRCs were calculated two approaches within...

The photochemistry of a model merocyanine-spiropyran system was analyzed theoretically at the MS-CASPT2//SA-CASSCF(14,12) level. Several excited singlet states were studied in both closed spiropyran and open merocyanine forms, paths to different S(1)/S(0) conical intersections found analyzed. After absorption UV light from form, there are two possible ultrafast routes efficient conversion ground state; one involves rupture C(spiro)-O bond leading form other lengthening C(spiro)-N with no...

The reactant cluster and transition state for epoxidation of allyl alcohol with peroxyformic acid have been located at the MP2/6-31G(d) level theory. free energy activation (Δ = 19.8 kcal/mol) predicted MP4//MP2/6-31G(d) is quite comparable experimental data 3-hydroxycyclohexene 19.7 kcal/mol). A spiro (TS) was found where plane defined by peroxyacid moiety oriented 89° to CC bond axis. Intrinsic reaction coordinate analysis suggests that after barrier crossed a 1,4-hydrogen migration...

Molecular tweezers are simple molecular receptors that can be characterized by the presence of two flat pincers separated a more or less rigid tether. They have ability to form complexes with substrate molecule gripping between tips in similar manner mechanical tweezers. Klärner et al. synthesized one structurally simplest tweezers, which is reported bind electrodeficient aromatic and aliphatic substrates as well organic cations. Complexes these electron-rich aromatic, aliphatic, anionic not...

Multiconfigurational CASSCF and CASPT2 calculations were performed to investigate the enol → keto tautomerization in lowest singlet excited state of 7-hydroxyquinoline·(NH3)3 cluster. Two different reaction mechanisms explored. The first one corresponds that proposed previously by Tanner et al. (Science 2003, 302, 1736) on basis experimental observations optimizations under Cs-symmetry constraints. This mechanism comprises four consecutive steps involves nonadiabatic transitions between...

Various high levels of theory have been applied to the characterization two higher lying biradicaloid metastable singlet states peroxynitrous acid. A minimum (cis-2) was located that had an elongated O−O distance (2.17 Å) and only 12.2 kcal/mol [UB3LYP/6-311+G(3df,2p)+ZPVE] in energy than its ground-state precursor. trans-metastable (trans-2) 10.9 HO−ONO. CASSCF(12,10)/6-311+G(d,p) calculations predict optimized geometries these cis- singlets be close those obtained with DFT. Optimization...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTNovel Structural Modifications Associated with the Highly Efficient Internal Conversion of 2-(2'-Hydroxyphenyl)benzotriazole Ultraviolet StabilizersCarlos M. Estévez, Robert D. Bach, K. C. Hass, and W. F. SchneiderView Author Information Department Chemistry Biochemistry University Delaware, Newark, Delaware 19716 Ford Research Laboratory, SRL MD-3028 Dearborn, Michigan 48121-2053 Cite this: J. Am. Chem. Soc. 1997, 119, 23,...

Various high levels of theory (DFT, QCISD, BD(TQ), and CASSCF) have been applied to the characterization two higher-lying biradicaloid singlet states peroxynitrous acid. A minimum (cis-2) was located that had an elongated O−O distance 2.17 Å only 14.4 kcal/mol [UB3LYP/6-311+G(3df,2p)] higher in energy than its cis-peroxynitrous acid ground-state precursor. trans metastable (trans-2) 12.8 HO−ONO. Complete active space calculations [CAS(12,10)/6-311+G(d,p)] predicted optimized geometries these...

The photodissociation of formic acid at 248 and 193 nm was investigated by classical trajectory RRKM calculations using an interpolated potential energy surface, iteratively constructed the B3LYP/aug-cc-pVDZ level calculation. Several sampling schemes in ground electronic state were employed to explore possibility conformational memory acid. CO/CO2 branching ratios obtained from trajectories initiated cis trans conformers are almost identical each other very good accordance with results. In...

Several structural modifications to the original molecular tweezers of Klärner's group were made with aim improving its binding capacity towards anions. The proposed raise electrostatic potential inside cavity and provide more conformational flexibility. complexes these new molecules halide anions Cl(-), Br(-), I(-) optimized at MPW1B95/6-31+G* level theory. interactions analyzed by single point density fitted local second-order Møller-Plesset perturbation theory (DF-LMP2) DF-LMP2...

The impact of the solvent environment on stabilization complexes formed by fluorine (T-F) and cyanide (T-CN) substituted tweezers with halide anions has been investigated theoretically. study was carried out using computational methodologies based density functional theory (DFT) symmetry adapted perturbation (SAPT). Interaction energies were obtained at M05-2X/6-31+G* level. results show a large stability in solvents dielectric constant prove suitability these molecular as potential hosts...

The microsolvation study of a group amines with variable number water molecules was performed by conducting theoretical analysis the properties clusters formed up to seven water. We describe several focusing on dissociation molecule that transfers proton amine and forms hydroxide ion. Ab initio calculations were these employing DFT/B3LYP MP2 methods 6-311++G(2d,p) basis set. Several stationary points for each cluster thus located characterized as minima from frequency calculations....

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of Some Pyrrolo[4,3,2-de]quinolinesPiotr Balczewski, John A. Joule, Carlos Estevez, and Mercedes AlvarezCite this: J. Org. Chem. 1994, 59, 16, 4571–4575Publication Date (Print):August 1, 1994Publication History Published online1 May 2002Published inissue 1 August 1994https://pubs.acs.org/doi/10.1021/jo00095a037https://doi.org/10.1021/jo00095a037research-articleACS PublicationsRequest reuse permissionsArticle...

The bond dissociation energies for a series of silyl peroxides have been calculated at the G2 and CBS-Q levels theory. A comparison is made with O-O BDE corresponding dialkyl peroxides, effect strength on activation barrier oxygen atom transfer discussed. enthalpies (DeltaH(298)) bis (trimethylsilyl) peroxide (1) trimethylsilyl hydroperoxide (2) are 54.8 53.1 kcal/mol, respectively (MP2) computed G2(MP2) bis(tert-butyl) tert-butyl 45.2 48.3 respectively. height 1,2-methyl migration from...

A theoretical study of the reaction S with C2H has been carried out. This is a possible step in generation sulfur-containing cumulenes interstellar clouds and circumstellar envelopes. The potential energy surfaces were computed by means G2, G2(QCI), CBS-Q methods case local minima saddle points. profiles for interaction all states associated lowest electron configurations have received special attention. MR-AQCC/aug-cc-pVTZ method was used as basic level computation; spin−orbit interactions...