Journal ArticleDOI
Planar transition structures in the epoxidation of alkenes. A DFT study on the reaction of peroxyformic acid with norbornene derivatives.
TLDR
The theoretical data correctly reproduce the experimental facial syn selectivity of norbornene and norbornadiene epoxidations and compare well with the experimental activation free energies of the peroxy acid epoxidation of all the olefins reported here.Abstract:
We studied, with the RB3LYP/6-311+G(d,p) method, the mechanism of peroxyformic acid epoxidation of norbornene, norbornadiene, tetramethylethene, and anti- and syn-sesquinorbornenes. The transition structures (TSs) for the reaction of tetramethylethene and norbornene show a perfect spiro geometry (the peroxy acid plane is perpendicular to the CC bond axis) with synchronous bond formation. Also three out of the four TSs of the norbornadiene reaction are spiro-like, but the highly asynchronous syn,endo-TS has a planar-like geometry. anti- and syn-sesquinorbornenes are substrates that, because of steric constraints, cannot easily accommodate spiro-like TSs. In fact, we managed to locate only a planar-like TS and a planar TS (the peroxy acid plane contains the CC bond axis), respectively, for these substrates. These planar TSs are “nonconcerted” since they are strongly unsymmetrical and only one of the C−O bonds of the oxirane ring is significantly formed. IRC analysis, while confirming that formation of one C...read more
Citations
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Journal ArticleDOI
Quantitative DFT modeling of the enantiomeric excess for dioxirane-catalyzed epoxidations
TL;DR: It is shown that transition state modeling at the UB3LYP-DFT/6-31G* level of theory can accurately model enantioselectivity for various dioxirane-catalyzed asymmetric epoxidations and all the synthetically useful high selectivities are successfully "predicted" by this method.
Journal ArticleDOI
Concerning the reactivity of dioxiranes. Observations from experiments and theory.
TL;DR: Rate data, which estimate Hammett "rho" values for the epoxidation of 3- or 4-substituted cinnamonitriles X x Ph-CH=CH-CN, unequivocally allow one to establish that dioxiranes epoxidize electrophilically even alkenes carrying electron-withdrawing groups.
Journal ArticleDOI
Reassessment of the Level of Theory Required for the Epoxidation of Ethylene with Dioxiranes
TL;DR: In this article, a single point energy correction at the BD(T)/6-311+G(d,p) level on these CASSCF geometries suggests that the C1 TS is only 0.6 kcal/mol lower in energy than an symmetrical spiro TS.
Journal ArticleDOI
Hydrotalcites composition as catalysts: Preparation and their behavior on epoxidation of two bicycloalkenes
Daniel Carriazo,Cristina Martín,Vicente Rives,Angela Popescu,Bogdan Cojocaru,Iuliana Mandache,Vasile I. Pârvulescu +6 more
TL;DR: In this paper, hydrotalcites containing heptamolybdate (Mo 7 O 24 6 - ) in the interlayer and Al combined with different divalent cations (Mg, Zn, Ni) in the brucite-like layers were prepared by ion exchange from suitable precursors containing terephthalate.
Journal ArticleDOI
Computational modeling of a stereoselective epoxidation: reaction of carene with peroxyformic acid.
TL;DR: Electronic structure theory was used to model the epoxidation of 3-carene by peroxyformic acid, and the proton shieldings calculated for the trans-epoxide correlated much more closely to the experimental values for the major ep oxidation product than did the shieldings Calculated for the cis-EPoxide, serving to verify the identity of the major product.
References
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Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
TL;DR: Numerical calculations on a number of atoms, positive ions, and molecules, of both open- and closed-shell type, show that density-functional formulas for the correlation energy and correlation potential give correlation energies within a few percent.
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A New Mixing of Hartree-Fock and Local Density-Functional Theories
TL;DR: In this article, a new coupling of Hartree-Fock theory with local density functional theory was proposed to improve the predictive power of the Hartree−Fock model for molecular bonding, and the results of tests on atomization energies, ionization potentials, and proton affinities were reported.
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Quantum Calculation of Molecular Energies and Energy Gradients in Solution by a Conductor Solvent Model
Vincenzo Barone,Maurizio Cossi +1 more
TL;DR: In this paper, a new implementation of the conductor-like screening solvation model (COSMO) in the GAUSSIAN94 package is presented, which allows Hartree−Fock (HF), density functional (DF) and post-HF energy, and HF and DF gradient calculations: the cavities are modeled on the molecular shape, using recently optimized parameters, and both electrostatic and nonelectrostatic contributions to energies and gradients are considered.
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Molecular Interactions in Solution: An Overview of Methods Based on Continuous Distributions of the Solvent
Jacopo Tomasi,Maurizio Persico +1 more
Journal ArticleDOI
Application of the pople-santry-segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane
TL;DR: In this article, the CNDO method has been applied to the cyclopropylcarbinyl and cyclobutyl cations, and has given results which are in very good accord with experimental data.