Kinetics of the thermal isomerization of 1,1‐dimethylcyclopropane

Kalra, Bansi L.; Lewis, David

doi:10.1002/kin.10008

Cited by 6 publications

(4 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The isomerization of CP was used as the internal thermometer in our earlier studies of other methylcyclopropane isomerizations [2,3,6], but we were concerned that, in spite of the relatively high total pressures and reactant loadings in the shock tube, the CP Figure 1 Arrhenius plot for 1,1,2,2-tetramethylcyclopropane isomerization; ᭺ Runs with CH added; ᭹ runs with CP added.…”

Section: Resultsmentioning

confidence: 99%

“…reaction rate might have been slowed by unimolecular falloff. In studies comparing rates of CP and MCP or di-MCP isomerizations [2,3], the similarities of the reactant and reference molecules (similar numbers of active vibrations) should have caused a canceling effect of any minor rate reductions due to low-pressure falloff that may have occurred. But we were less certain that would be the case when comparing isomerization rates of molecules as different as CP (nine atoms) and tetra-MCP (21 atoms).…”

Section: Figurementioning

confidence: 96%

“…Cell #4 had been used, and continues to be used, for hydrocarbon isomerization/decomposition studies, and has not produced unexpected products or behavior from any other reactant. The only clue is that, in some rate studies that preceeded the study of tetra-MCP isomerization, Lewis acids BCl 3 and BBr 3 were introduced into that cell to examine their catalytic effect on rates of structural and geometric isomerizations of many hydrocarbons, including other alkyl-substituted cyclopropanes [12]. However, experiments including those Lewis acids had also been carried out in two of the other three reactor cells, and no 2,2,3-TMB has been detected in the products of experiments run in those cells.…”

Section: Figurementioning

confidence: 98%

“…Previous kinetic studies have shown that as methyl groups are substituted for H atoms on the cyclopropane ring, activation energies for structural isomerization decrease, at least through the series cyclopropane, E a = 65.0 kcal/mol [1]; methylcyclopropane (MCP) 64.4 kcal/mol [2]; 1,1-dimethylcyclopropane (di-MCP), 61.8 kcal/mol [3]; and 1,2-dimethylcyclopropane, 61.2-62.3 kcal/mol [4]. This trend has been attributed to a weakening of the C C bonds in the highly strained cyclopropane ring, leading to a lower energy barrier for formation of a diradical intermediate.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Kinetics of the thermal isomerization of 1,1,2,2‐tetramethylcyclopropane

Lewis

Gray

Katsva

et al. 2006

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

Reaction rates for the structural isomerization of 1,1,2,2-tetramethylcyclopropane to 2,4-dimethyl-2-pentene have been measured over a wide temperature range, 672-750 K in a static reactor and 1000-1120 K in a single-pulse shock tube. The combined data from the two temperature regions give Arrhenius parameters E a = 64.7 (±0.5) kcal/mol and log 10 (A, s −1 ) = 15.47 (±0.13). These values lie at the upper end of the ranges of E a and log A values (62.2-64.7 kcal/mol and 14.82-15.55, respectively) obtained from three previous experimental studies, each of which covered a narrower temperature range. The previously noted trend toward lower E a values for structural isomerization of methylcyclopropanes as methyl substitution increases extends only through the dimethylcyclopropanes (1,1-and 1,2-); E a then appears to increase with further methyl substitution. In contrast, the pre-exponential factors for isomerization of cyclopropane and all of the methylcyclopropanes through tetramethylcyclopropane lie within ±0.3 of log 10 (A, s −1 ) = 15.2 and show no particular trend with increasing substitution. C 2006

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Figurementioning

confidence: 96%

Section: Figurementioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kinetics of the thermal isomerization of 1,1,2,2‐tetramethylcyclopropane

Lewis

Gray

Katsva

et al. 2006

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

show abstract

Kinetics of the thermal isomerization of 1,1,2‐trimethylcyclopropane

Lewis

Hughes

Miller

et al. 2006

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

The Arrhenius parameters for the gas phase, unimolecular structural isomerizations of 1,1,2-trimethylcyclopropane to three isomeric methylpentenes and two dimethylbutenes have been determined over a wide range of temperatures, 688-1124 K, using both static and shock tube reactors. For the overall loss of reactant, E a = 63.7 (± 0.5) kcal/mol and log 10 A = 15.28 (± 0.12). These values are higher by 2.6 kcal/mol and 0.7-0.8 than previously reported from experimental work or predicted from thermochemical calculations. E a for the formation of trans-4-methyl-2-pentene is 1.5 kcal/mol higher than E a for the formation of the cis isomer, which is identical to the E a difference previously reported for the formation of trans-and cis-2-butene from methylcyclopropane. Substitution of methyl groups for hydrogen atoms on the cyclopropane ring is expected to weaken the C C ring bonds, and it has been reported previously that activation energies for structural isomerizations of methylcyclopropanes do decrease substantially over the series cyclopropane > methylcyclopropane > 1,1-or 1,2-dimethylcyclopropane. However, the present study shows that the trend does not continue beyond dimethylcyclopropane isomerization. Besides reductions in C C bond energy, steric interactions may be increasingly important in determining the energy surface and conformational restrictions near the transition state in isomerizations of the more highly substituted methylcyclopropanes.

show abstract