Mechanisms of front-side substitutions. The transition states for the SNi decomposition of methyl and ethyl chlorosulfite in the gas phase and in solution

1994 ◽  
Vol 59 (7) ◽  
pp. 1849-1854 ◽  
Author(s):  
Peter R. Schreiner ◽  
Paul von Rague Schleyer ◽  
Richard K. Hill
Keyword(s):  
Gas Phase ◽  
Transition States ◽  
Front Side

Theoretical Study of the Kinetics and Mechanism of the Thermal Decomposition of 3-Oxetanone in the Gas Phase

2017 ◽  
Vol 42 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Mohammad Khavani ◽  
Javad Karimi
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Ethylene Oxide ◽  
Gas Phase ◽  
Transition States ◽  
Decomposition Reaction ◽  
Kinetics And Mechanism ◽  
Methyl Radical ◽  
Decomposition Products ◽  
Concerted Mechanism

The kinetics and mechanism of the thermal decomposition reaction of 3-oxetanone in the gas phase were studied using quantum chemical calculations. The major products of this reaction are formaldehyde, ketene, carbon monoxide, ethylene oxide, ethylene and methyl radical. Formaldehyde, ketene, carbon monoxide and ethylene oxide are the initial decomposition products and other species are the products of ethylene oxide decomposition. The results of B3LYP and QCISD(T) calculations reveal that thermal decomposition of 3-oxetanone to ethylene oxide and carbon monoxide is more probable than to formaldehyde and ketene from an energy viewpoint. Moreover, quantum theory of atoms in molecules and natural bond orbital analysis indicate that 3-oxetanone decomposition to formaldehyde, ketene, carbon monoxide and ethylene occurs via a concerted mechanism and bonds that are involved in the transition states have a covalent character. Moreover, the calculated changes in bond lengths in the transition states reveal that bond breaking and new bond formation occur asynchronously in a concerted mechanism.

scholarly journals Theoretical Study of the Pyrolysis of Methyltrichlorosilane in the Gas Phase. 2. Reaction Paths and Transition States

2007 ◽  
Vol 111 (8) ◽  
pp. 1475-1486 ◽  
Author(s):  
Yingbin Ge ◽  
Mark S. Gordon ◽  
Francine Battaglia ◽  
Rodney O. Fox
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Transition States ◽  
Phase 2 ◽  
Reaction Paths

ChemInform Abstract: Gorin Models for Simple-Fission Transition States in the Gas Phase

ChemInform ◽  
2010 ◽  
Vol 26 (9) ◽  
pp. no-no
Author(s):  
R. G. GILBERT ◽  
I. G. PITT
Keyword(s):  
Gas Phase ◽  
Transition States

Hydration of acetone in the gas phase and in water solvent

2010 ◽  
Vol 88 (1) ◽  
pp. 56-64 ◽  
Author(s):  
Kiyull Yang ◽  
Yih-Huang Hsieh ◽  
Chan-Kyung Kim ◽  
Hui Zhang ◽  
Saul Wolfe
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Isotope Effects ◽  
Bond Formation ◽  
Transition States ◽  
Water Solvent ◽  
Cooperative Process

In water solvent, the hydration of acetone proceeds by a cyclic (cooperative) process in which concurrent C–O bond formation and proton transfer to oxygen take place through a solvent and (or) catalyst bridge. Reactivity is determined primarily by the concentration of a reactant complex and not the barrier from this complex. This situation is reversed in the gas phase; although the concentrations of reactive complexes are much higher than in solution, the barriers are also higher and dominant in determining reactivity. Calculations of isotope effects suggest that multiple hydron transfers are synchronous in the gas phase to avoid zwitterionic transition states. In solution, such transition states are stabilized by solvation and hydron transfers can be asynchronous.

Marcus theory and the existence or non-existence of transition states in gas phase deprotonation of carbon acids

1984 ◽  
Vol 62 (8) ◽  
pp. 1465-1469 ◽  
Author(s):  
Saul Wolfe
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Transition States ◽  
Marcus Theory ◽  
Energy Change ◽  
Transfer Reactions ◽  
Gas Phase Reactions ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Computational Level

At the 3-21G (3-21G*) computational level, the intrinsic barriers associated with proton transfer between XCH2− and CH3X have been found to be essentially constant (ca. 10 kcal/mol) for X = H, F, SH, Cl. According to the Marcus rate-equilibrium treatment of proton transfer reactions, this result means that transition states should not exist for gas phase reactions [Formula: see text], when the energy change exceeds 20 kcal/mol. This prediction has been confirmed for two cases (X = H, F) in which the energy change is less than 20 kcal/mol, and two cases (X = SH, Cl) in which the energy change is greater than 20 kcal/mol.

Temperature Dependence of Disproportionation–Combination Ratios for Alkyl Radicals in Liquid Methane

1971 ◽  
Vol 49 (17) ◽  
pp. 2861-2867 ◽  
Author(s):  
Hugh A. Gillis
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Transition States ◽  
Alkyl Radicals ◽  
Liquid Methane ◽  
Ethyl Radicals

The ratios of rate constants for disproportionation to combination have been measured for ethyl radicals and for i-propyl radicals in liquid methane between −181 and −94 °C. The radicals were generated by γ-radiolysis of dilute methane solutions of ethylene-d4 or propylene-d6. The activation energy for combination was found to exceed that for disproportionation by 290 ± 30 cal mol−1 for ethyl radicals and by 255 ± 25 cal mol−1 for i-propyl radicals. In both cases the disproportionation—combination ratio in the liquid, extrapolated to room temperature, is greater than that in the gas phase by a factor of about 2.5. These results are interpreted as indicating that disproportionation and combination reactions proceed by way of different transition states.

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