Studies with a Single-Pulse Shock Tube. III. The Thermal Isomerization of Methyl Isocyanide

Lifshitz, Assa; Carroll, Harvey F.; Bauer, S. H.

doi:10.1021/ja01062a006

Cited by 18 publications

(5 citation statements)

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“…Extrapolating k,(T) to 828 K and reducing it to 220 torr via the standard model RRKM calculation for this temperature suggests that the rate constant ought to be about 1.3-1.5 X lo3 s-l, compared with the actual values obtained of 332 and 359 s-l. Part of this discrepancy could be removed if argon were to be a much less efficient collider at higher temperatures, but not all of it. In fact, excellent agreement with our Table I1 of their paper (17), which is of course even less than p(CH3NC) itself by a factor of 828/298.…”

Section: Resultssupporting

confidence: 89%

The thermal isomerisation of methyl isocyanide in the temperature range 120–320 °C

Collister¹,

Pritchard²

1976

Can. J. Chem.

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Can. J. Chem. 54,2380(1976. The thermal isomerisation of methyl isocyanide has been measured in the rigorous absence of self-heating over a temperature range from 120-320 "C and at pressures from 2-100 torr. Expressions are given for the rate constant as functions of both temperature and pressure in these ranges of the two variables. The infinite-pressure rate constant is accurately represented by an Arrhenius line with no curvature having E , = 38.2 + 0.2 kcal mol-1 and loglo A , (s-1) = 13.35 + 0.11, although at all other pressures, E is a function of temperature.A number of tests on the cleanliness of the reaction were made, and some previously expressed concerns about side reactions are alleviated considerably. On a effectuC un certain nombre d'essais pour vCrifier la propretC de la reaction; on considere que quelques unes des inquietudes exprimks antkrieurement concernant les rkctions secondaires avaient Ct C grossierement surestimks. JOHN LEWIS COLLISTER et[Traduit par le journal] B Introductiontemperature range was made as wide as possible It has been suggested recently that the explosive isomerisation of methyl isocyanide may prove to be a sensitive and reliable standard against which to test theories of gaseous thermal explosions (1); the required kinetic and thermodynamic data on methyl isocyanide and its iiomerisation are, however, incdmplete for this purpose. As far as the kinetics of the isomerisation are concerned, the rate of the reaction has been studied extensively as a function of pressure at three temperatures only, 200, 230, and 260 OC (2), and extrapolation of these rates into the explosion region (310-360 OC) is very sensitive to small imperfections in the data. The uncertainty of this extrapolation is aggravated by the fact that in some experiments a correction had to be ma8e for self-heating in the reaction, and this correction although small, is itself rather uncertain, giving rise to possible errors in the required extrapolated data. In the work described in this paper, self-heating was eliminated by the appropriate choice of reaction-vessel size for the temperature and pressure in question, and the

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Section: Resultssupporting

confidence: 89%

The thermal isomerisation of methyl isocyanide in the temperature range 120–320 °C

Collister¹,

Pritchard²

1976

Can. J. Chem.

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“…The value of 35.19 kcal/mol agrees with values of ∼38.5 kcal/mol derived from the results of a kinetic study on various R−NC → R−CN rearrangements using photoelectron spectroscopy 38 and with a value of 35.0 kcal/mol calculated at the QCISD(T)/6-311G**//B3LYP/6-31G** level of theory . It is also in excellent agreement with a value of 38.4 kcal/mol obtained in the single-pulse shock tube experiments on the CH 3 NC → CH 3 CN isomerization. , Similar results were obtained recently by Zhou and Liu 12 at the B3LYP/6-311++G(2d,2p)//B3LYP/6-31G** level.…”

Section: Resultssupporting

confidence: 87%

Isomerization of Indole. Quantum Chemical Calculations and Kinetic Modeling

Dubnikova

Lifshitz

2001

J. Phys. Chem. A

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Density functional theory calculations were carried out to investigate the pathways of the unimolecular isomerizations of indole. Equilibrium and transition-state structures were optimized by the Lee−Yang−Parr correlation functional approximation (B3LYP) using the Dunning correlation-consistent polarized double-ξ basis set. Energy values were calculated at the CCSD(T) level of theory. Rate parameters for all the steps on the surfaces of the indole isomerizations were evaluated using B3LYP frequencies and CCSD(T)//B3LYP energy values. 3H-Indole, which is a stable tautomer of indole, is a precursor in the formation of o-tolyl isocyanide that by −NC → −CN flip forms o-tolunitrile. The latter is one of the isomers of indole. A second isomer, phenylacetonitrile, is obtained directly from indole. A kinetics scheme containing all the elementary steps on the surfaces was constructed, apparent rate constants for product formation were calculated, and comparison with experimentally available formation rates was made. The agreement for phenylacetonitrile is excellent. For o-tolunitrile the calculations somewhat underestimate the rate. Despite many efforts, a reaction path for the formation of m-tolunitrile based on indole as a starting point could not be calculated with activation energies compatible with the experimental findings. On the other hand, a reaction path for the isomerization starting from indole radical, with low-lying transition states and intermediates, was calculated. It is therefore suggested that indole radicals that are formed by various abstraction reactions are involved in the isomerization of indole to m-tolunitrile.

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“…From experimental results obtained in the 1960s, a molecular path was proposed with a 4C transition state located well below the dissociation threshold of either reactant. 21 It was also argued that vibrational excitation of the reactants is much more effective for reactivity than equivalent amounts of translational energy. 22 Experiments were not, however, completely conclusive since it was found that low levels of impurities played a rather important role.…”

Section: Introductionmentioning

confidence: 99%

Four-center reactions: A quantal model for H4

Hernández

Clary

1996

The Journal of Chemical Physics

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Analytical potential energy surface for the CH4+ClCH3+ClH reaction: Application of the variational transition state theory and analysis of the kinetic isotope effects J. Chem. Phys. 105, 3517 (1996) We develop a quantal model for studying four-center reactions, A 2 ϩB 2 →2AB, and collision induced dissociation A 2 ϩB 2 →AϩB 2 ϩA. The method involves using hyperspherical coordinates to describe vibrations of the A 2 and B 2 bonds and a global vibration and rotation of the exchange products. Application to the H 4 system is presented, using a realistic potential energy surface. The reaction goes through a four-center linear transition state located just above the dissociation threshold. In the energy range studied ͑5-5.5 eV͒, collision induced dissociation competes with the four-center reaction and is the dominant process. It is found that vibrational energy, originally deposited in one of the diatomic partners, is much more efficient than translational energy in promoting reaction. Vibrational and rotational final distributions show that the products are internally hot. This simple quantal model, yet very demanding computationally, illustrates in detail many features of the H 4 dynamics above the dissociation threshold, and could serve to study other four center reactions with trapezoidal or linear transition states.

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Studies with a Single-Pulse Shock Tube. III. The Thermal Isomerization of Methyl Isocyanide

Cited by 18 publications

References 0 publications

The thermal isomerisation of methyl isocyanide in the temperature range 120–320 °C

The thermal isomerisation of methyl isocyanide in the temperature range 120–320 °C

Isomerization of Indole. Quantum Chemical Calculations and Kinetic Modeling

Four-center reactions: A quantal model for H4

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