Unimolecular Rate Constants for the HF and HCl Elimination Reactions from Chemically Activated CF2 ClSH

2015 ◽  
Vol 47 (6) ◽  
pp. 379-388
Author(s):  
Samuel M. Rossabi ◽  
Kylie C. Smith ◽  
George L. Heard ◽  
Bert E. Holmes
Keyword(s):  
Rate Constants ◽  
Elimination Reactions

The Elimination Reactions of Some Alkyl Cyanides in the Gas Phase

1973 ◽  
Vol 51 (3) ◽  
pp. 366-369 ◽  
Author(s):  
P. N. Dastoor ◽  
E. U. Emovon
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Rate Constants ◽  
Flow System ◽  
Elimination Reactions ◽  
Kinetics Of

The kinetics of the thermal decomposition of ethyl, isopropyl, and t-butyl cyanides into HCN and the corresponding defines have been studied in a seasoned silica vessel in a flow system in the absence and presence of toluene as inhibitor. The reactions are homogeneous and the unimolecular rate constants are expressible by the following Arrhenius equations:[Formula: see text]

Thermal Ion-Molecule Reactions in Oxygen-Containing Molecules. Condensation-Elimination Reactions in Dimethyl Ether-Trioxane Mixtures

1977 ◽  
Vol 32 (12) ◽  
pp. 1533-1540 ◽  
Author(s):  
Minoru Kumakura ◽  
Toshio Sugiura
Keyword(s):  
Isotope Effect ◽  
Dimethyl Ether ◽  
Mass Spectrometer ◽  
Rate Constants ◽  
Linear Structure ◽  
Ionization Efficiency ◽  
Ion Molecule Reactions ◽  
Fragment Ions ◽  
Product Ions ◽  
Elimination Reactions

Abstract Thermal ion-molecule reactions in dimethyl ether - trioxane mixtures have been studied with a time-of-flight mass spectrometer. The appearance potentials and ionization efficiency curves of product and major fragment ions were measured by an RPD technique. The product ions, having a linear structure such as CH3OCH3(CH2O)n+, CH3OCH3(CH2O)nH+, CH3OCH2(CH2O)n+, and CH3OCH2(CH2O)nH+ (n = 1 - 3), are formed by condensation-elimination reactions of CH3OCH3+ and CH3OCH2+ with trioxane. The formation of the product ions involves the dissociation of an intermediate-complex, which has a linear structure. It was found that homo-elimination of neutral products occurs preferentially from the trioxane molecule site in the complex. Extensive scrambling does not take place. The rate constants for the ions formed in dimethyl ether (or dimethyl-d6 ether) - trioxane mixtures are obtained, and a small isotope effect is observed. The rate constants of the condensation-elimination reactions of CH3OCH2+ with trioxane are compared with those with dimethyl ether.

Primary isotope effects and mechanism of base initiated β-elimination reactions of di-(p-nitrophenyl)fluoroethanes

1977 ◽  
Vol 55 (10) ◽  
pp. 1696-1700 ◽  
Author(s):  
Jan Kurzawa ◽  
Kenneth T. Leffek
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Sodium Methoxide ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Second Order ◽  
Order Rate ◽  
Elimination Reactions

The second-order rate constants have been determined for the β-elimination reactions of 2,2-di-(p-nitrophenyl)-1,1,1-trifluoroethane, 2,2-di-(p-nitrophenyl)-1-fluoroethane, and their β-deuterated analogues with sodium methoxide in methanol. The primary isotope effects and activation parameters for these reactions are reported. It is suggested that the trifluoro-compound reacts via the pre-equilibrium carbanion mechanism (ElcB)R and that the monofluoro compound follows the E2 mechanism via a carbanion-like transition state.

Kinetics and isotope effects of the β-elimination reactions of some 2,2-di(4-nitrophenyl)chloroethanes promoted by tetramethylguanidine in aprotic solvents

1985 ◽  
Vol 63 (6) ◽  
pp. 1194-1197 ◽  
Author(s):  
Arnold Jarczewski ◽  
Malgorzata Waligorska ◽  
Kenneth T. Leffek
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Aprotic Solvents ◽  
Polar Solvents ◽  
Deuterium Isotope Effects ◽  
Elimination Reactions

Rate constants for the β-elimination of HCl from 2,2-di(4-nitrophenyl)-1,1-dichloroethane (I) and 2,2-di(4-nitrophenyl)-1,1,1-trichloroéthane (II) promoted by tetramethylguanidine in the aprotic solvents acetonitrile, tetrahydrofuran, and n-hexane have been measured. The activation parameters are characterized by small enthalpies of activation (4.1 to 7.3 kcal mol−1) and large negative entropies of activation (−35 to −50 cal mol−1 deg−1). The primary deuterium isotope effects at 20° C range from kH/kD = 4.8 to 10.3. The results are interpreted to indicate an (EcB)1 mechanism for both substrates I and II in acetonitrile solvent and an E2H or mixed (ElcB)1–E2H mechanism in the less polar solvents, tetrahydrofuran and n-hexane.

scholarly journals The influence of crown ethers on the kinetics of E1cB and E2 β-elimination reactions of di(4-nitrophenyl)fluoroethanes with sodium methoxide in methanol

1982 ◽  
Vol 60 (24) ◽  
pp. 3077-3080
Author(s):  
Kenneth T. Leffek ◽  
Grzegorz Schroeder
Keyword(s):  
Isotope Effect ◽  
Crown Ethers ◽  
Rate Constant ◽  
Rate Constants ◽  
Sodium Methoxide ◽  
Activation Parameters ◽  
Deuterium Isotope Effect ◽  
Kinetic Order ◽  
Elimination Reactions ◽  
Kinetics Of

The addition of crown ethers 1,4,7,10,13-pentaoxacyclopentadecane (15C5) and 1,4,7,10,13,16-hexaoxacyclooctadecane (18C6) in quantities equimolar to the base, to β-elimination reactions of 1,1,1-trifluoro-2,2-di(4-nitrophenyl)ethane and 1-fluoro-2,2-di(4-nitrophenyl)ethane promoted by sodium methoxide in methanol, has been investigated. In the E2 reaction of the monofluoro compound, the crown ethers caused no change in the kinetic order and only small changes in the second-order rate constants and activation parameters. The primary deuterium isotope effect was also unaltered by the presence of crown ethers.For the (E1cB)R reaction of the trifluoro compound, no change in kinetic order was found, but slightly larger rate constant changes and an increase in the isotope effect from kH/kD = 1.0 to 1.25 at 25 °C was observed. This is interpreted as an alteration in mechanism from (E1cB)R towards (E1cB)I.

Carbanion reactivity — σ-adduct formation and elimination in the reactions of the carbanion from bis(phenylsulfonyl)methane with 4-nitrobenzofurazan derivatives

2008 ◽  
Vol 86 (3) ◽  
pp. 225-229 ◽  
Author(s):  
Basim H.M. Asghar ◽  
Michael R Crampton ◽  
Chukwuemeka Isanbor
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Intrinsic Rate ◽  
Adduct Formation ◽  
Nmr Studies ◽  
H Nmr ◽  
A Value ◽  
Elimination Reactions ◽  
Intrinsic Rate Constant

1H NMR studies in [2H6]-DMSO show that the carbanion 4 from bis(phenylsulfonyl)methane reacts with 4,6-dinitrobenzofuroxan to yield a σ-adduct that undergoes base-catalysed elimination to yield an alkene derivative. Rate constants, measured spectrophotometrically, are reported for the corresponding reactions in methanol of 4 with 4-nitrobenzofurazan and some derivatives that give adducts at the 5-position. The intrinsic rate constant, ko, for this process has a value of 1.5 ± 0.5. The 5-adducts undergo methoxide-catalysed elimination of phenylsulfinic acid to yield alkene derivatives and rate constants for this process are reported.Key words: carbanions, 4-nitrobenzofurazan, σ-adducts, elimination reactions.

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