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Gas-phase Elimination (gas-phase + elimination)

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Chemistry100%

Selected Abstracts

The unimolecular elimination kinetics of benzaldoxime in the gas phase

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2007
Libia L. Julio
The kinetics of the gas-phase elimination of benzaldoxime was determined in a static reaction system over the temperature and pressure range 350°C,400°C and 56,140 Torr, respectively. The products obtained were benzonitrile and water. The reaction was found to be homogeneous, unimolecular, and tend to obey a first-order rate law. The observed rate coefficient is represented by the following Arrhenius equation: According to kinetic and thermodynamic parameters, the reaction proceeds through a concerted, semi-polar, four-membered cyclic transition state type of mechanism. © 2007 Wiley Periodicals, Inc. 39: 145,147, 2007 [source]

The mechanisms of the homogeneous, unimolecular, elimination kinetics of several , -substituted diethyl acetals in the gas-phase

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 2010
José R. Mora
Abstract The rates of gas-phase elimination of several , -substituted diethyl acetals have been determined in a static system and seasoned with allyl bromide. The reactions, inhibited with toluene, are homogeneous, unimolecular, and follow first-order law kinetics. These elimination processes involve two parallel reactions. The first parallel reaction yields ethanol and the corresponding ethyl vinyl ether. The latter product is an unstable intermediate and further decomposes to ethylene and the corresponding substituted aldehyde. The second parallel reaction gives ethane and the corresponding ethyl ester. The kinetics has been measured over the temperature range of 370,441,°C and pressure range of 23,160,torr. The rate coefficients are given by the following Arrhenius equations: The differences in the rates of ethanol formation may be attributed to electronic transmission of the , -substituent. The comparative kinetic and thermodynamic parameters of the parallel reactions suggest two different concerted polar four-membered cyclic transition state types of mechanisms. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Experimental and theoretical studies of the elimination kinetics of 3-hydroxy-3-methyl-2-butanone in the gas phase

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 7 2005
Mariana Graterol
Abstract The kinetics of the gas-phase elimination of 3-hydroxy-3-methyl-2-butanone was investigated in a static system, seasoned with allyl bromide, and in the presence of the free chain radical inhibitor toluene. The working temperature and pressure range were 439.6,489.3°C and 81,201.5,Torr (1,Torr,=,133.3,Pa), respectively. The reaction was found to be homogeneous, unimolecular and to follow a first-order rate law. The products of elimination are acetone and acetaldehyde. The temperature dependence of the rate coefficients is expressed by the following equation: log[k1(s,1)],=,(13.05±0.53),(229.7±5.3),kJ,mol,1 (2.303RT),1. Theoretical estimations of the mechanism of this elimination suggest a molecular mechanism of a concerted non-synchronous four-membered cyclic transition-state process. An analysis of bond order and natural bond orbital charges suggests that the bond polarization of C(OH),C(O),, in the sense of C(OH),+&·C(O),,, is rate limiting in the elimination reaction. The rate coefficients obtained experimentally are in reasonably good agreement with the theoretical calculations. The mechanism of 3-hydroxy-3-methyl-2-butanone elimination is described. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Kinetics of elimination of several heterocyclic carbamates in the gas phase,

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2002
Yannely Brusco
Abstract The kinetics of the gas-phase elimination of several heterocyclic carbamates were determined in a static system over the temperature range 190.0,409.7,°C and the pressure range 26.5,125,Torr (1,Torr,=,133.3,Pa). The reactions in seasoned vessels, with the free radical inhibitor cyclohexene and/or toluene always present, are homogeneous and unimolecular and obey a first-order rate law. The observed rate coefficients are represented by the following Arrhenius equations: for tert -butyl-1-pyrrolidine carboxylate, log k1 (s,1),=,(11.36,±,0.31) ,(145.4,±,3.1)­kJ,mol,1 (2.303RT),1; for 1-(tert -butoxycarbonyl)-2-pyrrolidinone, log k1 (s,1),=,(11.54,±,0.29) ,(140.8,±,2.8)­kJ,mol,1 (2.303RT),1; for tert -butyl-1-pyrrole carboxylate, log k1 (s,1),=,(12.12,±,0.05) ,(145.2,±,1.0),kJ,mol,1 (2.303RT),1; and for 1-ethylpiperazine carboxylate, log k1 (s,1),=,(12.05,±,0.19) ,(188.2,±,4.6),kJ,mol,1 (2.303RT),1. The saturated heterocyclic carbamates show a decrease in rates of elimination due to electronic factors. Heterocyclic carbamates with a nitrogen atom able to delocalize its electrons with ,-bonds present in the ring were found to enhance the rates due to resonance interactions. Copyright © 2002 John Wiley & Sons, Ltd. [source]