Transition structure for the epoxidation of alkenes with peroxy acids. A theoretical study

1991 ◽  
Vol 113 (6) ◽  
pp. 2338-2339 ◽  
Author(s):  
Robert D. Bach ◽  
Amy L. Owensby ◽  
Carlos Gonzalez ◽  
H. Bernard Schlegel ◽  
Joseph J. W. McDouall
Keyword(s):  
Theoretical Study ◽  
Transition Structure ◽  
Peroxy Acids ◽  
Epoxidation Of Alkenes

Mechanism of Acid-Catalyzed Epoxidation of Alkenes with Peroxy Acids

1997 ◽  
Vol 62 (15) ◽  
pp. 5191-5197 ◽  
Author(s):  
Robert D. Bach ◽  
Carlo Canepa ◽  
Julia E. Winter ◽  
Paul E. Blanchette
Keyword(s):  
Acid Catalyzed ◽  
Peroxy Acids ◽  
Epoxidation Of Alkenes

A theoretical study of silyl anions and radicals. Change of mechanism from vertex inversion to edge inversion with increasing substitution by halogens

1990 ◽  
Vol 68 (8) ◽  
pp. 1309-1316 ◽  
Author(s):  
A. C. Hopkinson ◽  
C. F. Rodriquez ◽  
M. H. Lien
Keyword(s):  
Theoretical Study ◽  
Single Point ◽  
Lone Pair ◽  
Basis Set ◽  
Transition Structure ◽  
Silyl Radicals ◽  
Inversion Mechanism

Structures for trivalent silyl anions [Formula: see text] and [Formula: see text], where n takes values from 0 to 3, have been optimized at the HF/6-31 + +G* level and single point calculations made at the MP2/6-31 + +G* level (core included). SiH3− and ions containing one halogen invert by the vertex mechanism in which the lone-pair has π-symmetry, and the monosubstituted ions have high barriers (SiH2F− 45.2 kcal/mol and SiH2Cl− 44.0 kcal/mol). Further substitution by halogens results in a change to the edge inversion mechanism involving a T-shaped transition structure with the lone-pair coplanar with the ligands. Barriers (kcal/mol) at the MP2/6-31 + +G* level including ZPE are lower than for the monosubstituted ions and are SiHF2− 35.0, SiF3− 35.9, SiHCl2− 28.4, and SiCl3−32.5. In SiLi3− edge inversion is preferred, but the surface is much flatter and the barrier is low (9.8 kcal/mol). Trivalent silyl radicals SiHnF(3−n), SiHnCl(3−n) and SiFnCl(3−n) (with n having values 0 to 3) have also been examined with the 6-31 + +G* basis set, with optimization at the UHF level and single point calculations at the UMP2 level. Radicals SiH3, SiH2F, SiH2Cl, and SiHCl2 all invert by the vertex mechanism. Increased halogenation results in a change of mechanism and SiF3, SiCl3, SiF2Cl, and SiFCl2 invert by the edge mechanism. For radical SiHF2 the calculated barriers for the two mechanisms are almost identical with the higher level of theory slightly favouring edge inversion. Keywords: inversion mechanism, halogenated silyl radicals and anions.

Theoretical study on the influence of H2O for the 1,2-hydrogen shift from hydrogen peroxide (H2O2) to water oxide (O-OH2)

2001 ◽  
Vol 79 (1) ◽  
pp. 22-28 ◽  
Author(s):  
Toshiya Okajima
Keyword(s):  
Hydrogen Peroxide ◽  
Theoretical Calculation ◽  
Theoretical Study ◽  
Stationary Points ◽  
Transition Structure ◽  
Hydrogen Shift ◽  
Heats Of Reaction ◽  
Diffusion Function ◽  
And Diffusion ◽  
Protic Media

Theoretical calculation was performed to study the solvent effect for the 1,2-hydrogen shift from hydrogen peroxide (H2O2) (1) to water oxide (O-OH2) (2). Stationary points including transition structures (TSs) were optimized with no geometrical constraint at Becke3LYP/6-311++G** level. All stationary points were tested by frequency analysis and IRC calculation. The activation energies (ΔE[Formula: see text]) and heats of reaction (ΔH0) were evaluated at Becke3LYP/6-311++G**//Becke3LYP/6-311++G** level of theory. The following points were clarified: (i) inclusion of polarization function (*) and diffusion function (+) for calculation hardly affected the energetic of the reaction; (ii) judging from the change of ΔE[Formula: see text] and ΔH0 values, the reaction is predicted to be accelerated by the increase of involving H2O; (iii) proton-relaying mechanism considerably reduced ΔE[Formula: see text] values; (iv) the endothermicity became monotonically small as the number of solvating H2O molecules increased. The calculation suggests that the formation of water oxide (O-OH2) (2) from H2O2 (1) is promoted by a proton-relaying pathway in protic media (such as H2O).Key words: theoretical calculation, ab initio, transition structure, 1,2-hydrogen shift, water oxide.

New molybdenum (VI) catalyst for the epoxidation of alkenes and oxidation of sulfides: An experimental and theoretical study

2014 ◽  
Vol 411 ◽  
pp. 61-66 ◽  
Author(s):  
Mojtaba Bagherzadeh ◽  
Mohammad Mehdi Haghdoost ◽  
Alireza Ghanbarpour ◽  
Mojtaba Amini ◽  
Hamid Reza Khavasi ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Oxidation Of Sulfides ◽  
Epoxidation Of Alkenes

A reinvestigation of the mechanism of epoxidation of alkenes by peroxy acids. A CASSCF and UQCISD study

2002 ◽  
Vol 43 (23) ◽  
pp. 4215-4219 ◽  
Author(s):  
Sergiy Okovytyy ◽  
Leonid Gorb ◽  
Jerzy Leszczynski
Keyword(s):  
Peroxy Acids ◽  
Epoxidation Of Alkenes
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