Kinetics of racemization and cis-trans isomerization of the optically active 1-ethyl-2-methylcyclopropanes in the gas phase. An estimate of relative rates of bond rotation and ring closure in diradical intermediates

1969 ◽  
Vol 91 (26) ◽  
pp. 7411-7425 ◽  
Author(s):  
Robert G. Bergman ◽  
William L. Carter
Keyword(s):  
Gas Phase ◽  
Optically Active ◽  
Ring Closure ◽  
Bond Rotation ◽  
Trans Isomerization ◽  
Kinetics Of

Carbonyl Ylides and the Rearrangement of (+)-trans-2,3-Diisopropenyloxirane

1974 ◽  
Vol 52 (11) ◽  
pp. 2098-2101 ◽  
Author(s):  
Jean-Claude Paladini ◽  
R. J. Crawford
Keyword(s):  
Gas Phase ◽  
Kinetic Data ◽  
Ring Opening ◽  
Ring Closure ◽  
Carbonyl Ylide ◽  
Kinetics Of ◽  
Oxygen Bond

The kinetics of the gas phase racemization and rearrangement of 2,3-diisopropenyloxirane have been determined. Comparison with the kinetic data for 2,3-divinyloxirane allows us to exclude the mechanism for the formation of vinyldihydrofuran wherein an inward conrotatory ring opening comprises the first step. The mechanism proposed consists of an isomerization about the carbon–oxygen bond of the carbonyl ylide to form an isomeric intermediate which then undergoes a disrotatory five-centered ring closure to produce 2-isopropenyl-4-methyl-2,3-dihydrofuran.

DFT studies on the diastereoselectivity and regioselectivity of multicomponent domino Knoevenagel/Diels–Alder reaction

2020 ◽  
Vol 19 (02) ◽  
pp. 2050005 ◽  
Author(s):  
Mina Attarbashi ◽  
Nader Zabarjad Shiraz ◽  
Marjaneh Samadizadeh
Keyword(s):  
Gas Phase ◽  
Alder Reaction ◽  
Diels Alder ◽  
Ring Closure ◽  
Dft Studies ◽  
Acid Base ◽  
Bond Rotation ◽  
Diels Alder Reaction ◽  
Difference Formula ◽  
State Formula

In this study, mechanism and stereochemistry of multicomponent domino Knoevenagel/Diels–Alder reaction were investigated theoretically. Structures of reagents, transition states, intermediates, and products were optimized at M062X/6-31[Formula: see text]G(d,p) level of theory. Although the mechanism of this reaction involved several processes, including bond rotation, isomerization, asymmetric cycloaddition, acid-base, and nucleophile–electrophile competitions, critical processes were studied to provide a clearer picture of the mechanism of this valuable reaction in terms of stereochemistry considerations. According to the results, the ring closure step of reaction performed via a polar Dield-Alder mechanism, having enthalpy at approximately 40[Formula: see text]kcal/mol. The diastereoselectivity of the reaction was controlled by the interaction of dienophile with the less hindered face of diene through a more stable endo transition state ([Formula: see text] and 27.31 in methanol and gas phase, respectively). HSAB criteria could explain the regioselectivity of this reaction by considering the least softness difference ([Formula: see text]) for interacting C-atoms based on Hirshfeld populations. The result was the creation of cis-spiro cyclohexanone under kinetic and thermodynamic controls as a predominant diastereoselective and regioselective product.

Synthesis of an optically active cyclopropene and kinetics of its thermal racemization in the gas phase. Intermediacy of a vinylcarbene

1973 ◽  
Vol 95 (17) ◽  
pp. 5680-5687 ◽  
Author(s):  
Eunice J. York ◽  
Wolfgang. Dittmar ◽  
J. Ronald. Stevenson ◽  
Robert G. Bergman
Keyword(s):  
Gas Phase ◽  
Optically Active ◽  
Kinetics Of

Rapid racemization of an optically active cyclopropene derivative via ring opening, bond rotation, and ring closure

1972 ◽  
Vol 94 (8) ◽  
pp. 2882-2883 ◽  
Author(s):  
Eunice J. York ◽  
Wolfgang Dittmar ◽  
J. Ronald Stevenson ◽  
Robert G. Bergman
Keyword(s):  
Ring Opening ◽  
Optically Active ◽  
Ring Closure ◽  
Bond Rotation

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

Solvent and viscosity effect on the kinetics of the thermal cis-trans isomerization of 3'-nitro-4-diethylaminoazobenzene

1989 ◽  
Vol 11 (3) ◽  
pp. 179-189 ◽  
Author(s):  
Bruno Marcandalli ◽  
Pier Luigi Beltrame ◽  
Ernestina Dubini-Paglia ◽  
Alberto Seves
Keyword(s):  
Viscosity Effect ◽  
Trans Isomerization ◽  
Kinetics Of
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