Rate parameters for the reactions of the bromomethyne radical

McDaniel, Robert S.; Dickson, R. Bruce; James, F. C.; Strausz, O. P.; Bell, T. N.

doi:10.1016/0009-2614(76)80774-9

Cited by 16 publications

(5 citation statements)

References 19 publications

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“…Dissociative photoionization of these brominated products could contribute to the ion signal at lower masses. However, the rate constants for reactions of radicals such as CBr with small unsaturated hydrocarbons are several orders of magnitude smaller at room temperature (<10 −12 cm 3 molecule −1 s −1 ), − than those for reactions of the CH radical. , Any contribution from dissociative ionization of brominated molecules can therefore be identified by inspection of the time trace of the species. Using this kinetic analysis, contribution from dissociative ionization of higher-mass species to the ion signal at various product masses has been identified only for the detection of C 3 H 3 cations and is negligible in other cases.…”

Section: Resultsmentioning

confidence: 99%

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

et al. 2009

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The reactions of the methylidyne radical (CH) with ethylene, acetylene, allene, and methylacetylene are studied at room temperature using tunable vacuum ultraviolet (VUV) photoionization and time-resolved mass spectrometry. The CH radicals are prepared by 248 nm multiphoton photolysis of CHBr 3 at 298 K and react with the selected hydrocarbon in a helium gas flow. Analysis of photoionization efficiency versus VUV photon wavelength permits isomer-specific detection of the reaction products and allows estimation of the reaction product branching ratios. The reactions proceed by either CH insertion or addition followed by H atom elimination from the intermediate adduct. In the CH + C 2 H 4 reaction the C 3 H 5 intermediate decays by H atom loss to yield 70(±8)% allene, 30(±8)% methylacetylene and less than 10% cyclopropene, in agreement with previous RRKM results. In the CH + acetylene reaction, detection of mainly the cyclic C 3 H 2 isomer is contrary to a previous RRKM calculation that predicted linear triplet propargylene to be 90% of the total H-atom co-products. High-level CBS-APNO quantum calculations and RRKM calculation for the CH + C 2 H 2 reaction presented in this manuscript predict a higher contribution of the cyclic C 3 H 2 (27.0%) versus triplet propargylene (63.5%) than these earlier predictions.Extensive calculations on the C 3 H 3 and C 3 H 2 D system combined with experimental isotope ratios for the CD + C 2 H 2 reaction indicate that H-atom assisted isomerization in the present experiments is responsible for the discrepancy between the RRKM calculations and the experimental results. Cyclic isomers are also found to represent 30(±6)% of the detected products in the case of CH + methylacetylene, together with 33(±6)% 1,2,3-butatriene and 37(±6)% vinylacetylene. The CH + allene reaction gives 23(±5)% 1,2,3-butatriene and 77(±5)% vinylacetylene, whereas cyclic isomers are produced below the detection limit in this reaction. The reaction exit channels deduced by comparing the product distributions for the aforementioned reactions are discussed in detail.3

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Section: Resultsmentioning

confidence: 99%

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

et al. 2009

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“…5 To our knowledge, kinetic data on the reactions of brominated radical species with pyrrole are unavailable. But, the reaction rate coefficients of the bromomethylidyne radical (CBr) with alkenes and alkynes at room temperature have been measured and found to be much smaller (o10 À12 cm 3 molecule À1 s À1 ) [31][32][33] than for analogous reactions with the CH radical (B10 À10 cm 3 molecule À1 s À1 ). 34,35 Based on these observations, it is reasonable to assume that the reaction of CBr with pyrrole is at least 100 times slower than the CH with pyrrole reaction.…”

Section: Resultsmentioning

confidence: 99%

Direct detection of pyridine formation by the reaction of CH (CD) with pyrrole: a ring expansion reaction

Soorkia

Taatjes

Osborn

et al. 2010

Phys. Chem. Chem. Phys.

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“…28,52 The three body reaction of the CH ( 2 , v=0) radical with molecular nitrogen is slow 53 at the pressure of the flow and is unlikely to affect the observed product distributions. Reactions of CBr with small unsaturated hydrocarbons are several orders of magnitude slower at the present temperature 46,47,50,[54][55][56] than those for reactions of the CH radical. 54,55,57,58 Similarly slow kinetics between CBr and amines would allow discriminating between CBr and CH reaction products.…”

Section: Resultsmentioning

confidence: 64%

“…The vibrationally excited CH(Χ 2 Π, v = 1) radicals are efficiently quenched by adding nitrogen to the main flow. , The three-body reaction of the CH (Χ 2 Π, v = 0) radical with molecular nitrogen is slow at the pressure of the flow and is unlikely to affect the observed product distributions. Reactions of CBr with small unsaturated hydrocarbons are several orders of magnitude slower at the present temperature ,,,− than those for reactions of the CH radical. ,,, Similarly, slow kinetics between CBr and amines would allow discriminating between CBr and CH reaction products. At 248 nm the singlet CHBr carbene is expected to be formed in very low concentrations compared to the CH radical .…”

Section: Resultsmentioning

confidence: 85%

Product Detection of the CH Radical Reactions with Ammonia and Methyl-Substituted Amines

et al. 2019

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Reactions of the methylidyne (CH) radical with ammonia (NH 3 ), methylamine (CH 3 NH 2 ), dimethylamine ((CH 3 ) 2 NH), and trimethylamine ((CH 3 ) 3 N), have been investigated under multiple collision conditions at 373 K and 4 Torr. The reaction products are detected using soft photoionization coupled to orthogonal acceleration time-of-flight mass spectrometry at the Advanced Light Source (ALS) synchrotron. Kinetic traces are employed to discriminate between CH reaction products and products from secondary or slower reactions. Branching ratios for isomers produced at a given mass and formed by a single reaction are obtained by fitting the observed photoionization spectra to linear combinations of pure compound spectra.The reaction of the CH radical with ammonia is found to form mainly imine, HN=CH 2 , in line with an addition-elimination mechanism. The singly methyl substituted imine is detected for the CH reactions with methylamine, dimethylamine, and trimethylamine. Dimethylimine isomers are formed by the reaction of CH with dimethylamine, while trimethylimine is formed by the CH reaction with trimethylamine. Overall, the temporal profiles of the products are not consistent with the formation of amino carbene products in the reaction flow tube. In the case of the reactions with methylamine and dimethylamine, product formation is assigned to an addition-elimination mechanism similar to that proposed for the CH reaction with ammonia.

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Rate parameters for the reactions of the bromomethyne radical

Cited by 16 publications

References 19 publications

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

Direct detection of pyridine formation by the reaction of CH (CD) with pyrrole: a ring expansion reaction

Product Detection of the CH Radical Reactions with Ammonia and Methyl-Substituted Amines

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