Energy transfer in thermal methyl isocyanide isomerization. Relative cross sections of fluoroalkanes and nitriles

Chan, Siu C.; Bryant, James T.; Spicer, Leonard D.; Rabinovitch, B. S.

doi:10.1021/j100909a003

Cited by 19 publications

(4 citation statements)

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“…ω has the form where β( T ) is the collision efficiency of the third body, Z ( T ) is the gas kinetic collision frequency, and P is the pressure. The collision frequency can be calculated with the standard formula . However, β( T ) is an empirical variable and must be estimated, usually with reference to an experimental value for the rate constant at high pressure.…”

Section: Resultsmentioning

confidence: 99%

Ab Initio and RRKM Studies of the Reactions of C, CH, and ¹CH₂ with Acetylene

1998

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We present ab initio calculations of geometries, energies, and normal mode frequencies for complexes and saddle points along the minimum energy reaction path for the reaction C + HCCH → C3H2 → C3H + H. We also present ab initio calculations along the minimum energy reaction path in the entrance channel for the reactions C + HCCH, CH + HCCH, and 1CH2 + HCCH. These results and those presented earlier by Walch are used to calculate rate constants for the reactions of C, CH, and 1CH2 with acetylene, using variational RRKM theory. The rate constants obtained agree well with experimental results for all three reactions. Unimolecular lifetimes for intermediate complexes associated with each reaction path are also presented. Among the more stable C3 isomers are propargyl and propargylene, which have lifetimes of 25 and 1900 ps, respectively, under thermal reaction conditions.

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Section: Resultsmentioning

confidence: 99%

Ab Initio and RRKM Studies of the Reactions of C, CH, and ¹CH₂ with Acetylene

1998

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“…Troe’s formulation of limiting low-pressure rate constants , also employed Z LJ as a reference collision frequency. One rationalization of this practice is that the measurements of relative collision efficiency − indicated that Z ( E ′) is at least proportional to Z LJ for sufficiently large bath gases. Although any inadequacies of this reference can be compensated for via the total cross-section factor , of the collision efficiency β c , this factor has been implicitly or explicitly assumed to be unity in many applications.…”

Section: Introductionmentioning

confidence: 99%

Collision Frequency for Energy Transfer in Unimolecular Reactions

Matsugi

2018

J. Phys. Chem. A

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Pressure dependence of unimolecular reaction rates is governed by the energy transfer in collisions of reactants with bath gas molecules. Pressure-dependent rate constants can be theoretically determined by solving master equations for unimolecular reactions. In general, master equation formulations describe energy transfer processes using a collision frequency and a probability distribution model of the energy transferred per collision. The present study proposes a novel method for determining the collision frequency from the results of classical trajectory calculations. Classical trajectories for collisions of several polyatomic molecules (ethane, methane, tetrafluoromethane, and cyclohexane) with monatomic colliders (Ar, Kr, and Xe) were calculated on potential energy surfaces described by the third-order density-functional tight-binding method in combination with simple pairwise interaction potentials. Low-order (including non-integer-order) moments of the energy transferred in deactivating collisions were extracted from the trajectories and compared with those derived using some probability distribution models. The comparison demonstrates the inadequacy of the conventional Lennard-Jones collision model for representing the collision frequency and suggests a robust method for evaluating the collision frequency that is consistent with a given probability distribution model, such as the exponential-down model. The resulting collision frequencies for the exponential-down model are substantially higher than the Lennard-Jones collision frequencies and are close to the (hypothetical) capture rate constants for dispersion interactions. The practical adequacy of the exponential-down model is also briefly discussed.

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“…The preparation and purification of methyl isocyanide, together with most of the experimental method has been described previously (3,4). Matheson propane and hexafluoroethane were purified by repeated bulb-to-bulb distillation: the former contained a small amount of methane; Phillips propylene (research grade) was used without further purification.…”

Section: Methodsmentioning

confidence: 99%

“…one to 100 atm of added propane "inert" gas and 1.3 atm of i~o c v a n i d e .~ Complications may arise at higher pressures, and in any case it has appeared desirable to investigate this subject at pressures near and below 1 atm, where most of the earlier work on unimolecular behavior has been performed (3)(4)(5). Wider variation of the nature of the inert gas and of its proportion to isocyanide is also desirable.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Free Radical Catalysis in Thermal Methyl Isocyanide Isomerization. Variation of Inert Gas Efficiency with k/k_∞

Fujimoto¹,

Wang²,

Rabinovitch³

1972

Can. J. Chem.

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Experiments have been made to assess the importance of radical chain effects in thermal isornerization of methyl isocyanide. Three bath gases. propylene, propane, and hexafluoroethane were studied at 230 C over a small region of fall-off. The relative dilution with propane was varied widely. A negative search was made for possible secondary radical products. The values of k , accord with earlier results in the pure system. It is believed that radical catalysis is minor. The observed collisional efficiency of the inert gases Dm(co) decreases with increase ofklk,, in accord with previous theoretical predictions.Nous avons effectue certains travaux dans le but de souligner I'importance des effets de chaines radicalaires dans I'isomerisation de I'isocyanure de mtthyle. Trois gaz porteurs ont ete etudiees a 230 "C dans une mince region de retombee, sort le propyltne, le propane et I'hexafluoroethane. La dilution relative avec le propane variait considerablement. Les recherches dans le but de trouver des produits secondaires radicalaires possibles se sont averees negatives. Les valeurs de k, sont en accord avec les resultats prtctdents avec le systkme pur. On croit que la catalyse radicalaire est minime. L'efficacitt de collision observee des gaz inertes, Dm(co) diminue avec I'augmentation de klk,, en accord avec les prkdictions thkoriques preckdentes.

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Energy transfer in thermal methyl isocyanide isomerization. Relative cross sections of fluoroalkanes and nitriles

Cited by 19 publications

References 0 publications

Ab Initio and RRKM Studies of the Reactions of C, CH, and ¹CH₂ with Acetylene

Ab Initio and RRKM Studies of the Reactions of C, CH, and ¹CH₂ with Acetylene

Collision Frequency for Energy Transfer in Unimolecular Reactions

Assessment of Free Radical Catalysis in Thermal Methyl Isocyanide Isomerization. Variation of Inert Gas Efficiency with k/k_∞

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Energy transfer in thermal methyl isocyanide isomerization. Relative cross sections of fluoroalkanes and nitriles

Cited by 19 publications

References 0 publications

Ab Initio and RRKM Studies of the Reactions of C, CH, and 1CH2 with Acetylene

Ab Initio and RRKM Studies of the Reactions of C, CH, and 1CH2 with Acetylene

Collision Frequency for Energy Transfer in Unimolecular Reactions

Assessment of Free Radical Catalysis in Thermal Methyl Isocyanide Isomerization. Variation of Inert Gas Efficiency with k/k∞

Contact Info

Product

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Ab Initio and RRKM Studies of the Reactions of C, CH, and ¹CH₂ with Acetylene

Ab Initio and RRKM Studies of the Reactions of C, CH, and ¹CH₂ with Acetylene

Assessment of Free Radical Catalysis in Thermal Methyl Isocyanide Isomerization. Variation of Inert Gas Efficiency with k/k_∞