Infrared photochemistry of halogenated ethylenes

Reiser, Christopher; Lussier, Frances M.; Jensen, Craig C.; Steinfeld, J. I.

doi:10.1021/ja00496a013

Cited by 79 publications

(28 citation statements)

References 9 publications

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“…They also observed only a single product (apart from HF) from the elimination reaction, indicating that it occurs via a concerted process. The same conclusion was reached by Steinfeld and co-workers (27) in their study of IRMPA of vinyl chloride using a C 0 2 laser, followed by the elimination reaction.…”

Section: Introductionsupporting

confidence: 77%

“…Specifically, it is unclear what is the internal energy distribution of the reacting molecules when excited by the laser. Moore and co-workers (25) and Steinfeld and co-workers (27) were able to explain their results using a statistical approach, the molecular internal energy distribution being represented by a non-specific-mode model, and the reaction rates being calculated by RRKM approach which assumes a rapid attainment of microcanonical internal equilibrium of the molecule prior to reaction. More rigorous master equation calculations (29) for IRMPA confirm the above; Steinfeld and co-workers (27) based their statistical model on these approaches.…”

Section: Introductionmentioning

confidence: 99%

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Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH₂CF₂ system

Beck¹,

Burns²

1984

Can. J. Chem.

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Although certain classes of reactions are known to occur via 4-centre transition states, there has been no irrefutable proof that in the gas phase addition reactions also proceed via a 4-centre concerted process. Results of recent information theory calculations on the HF(v) + CH2CF2 system indicate that it should be possible to observe reaction products for HF(v = 5).Results are presented here on experiments attempting to achieve laser-induced 4-centre addition of HF to several unsaturated molecules (C2H2, C2H4, C4H6, CH2CF2, and CF2CCIF). A mixture of HF and co-reactant was irradiated by a dye-laser tuned photo-acoustically to the fifth vibrational level of HF, and the resulting mixture was analysed by gas chromatography and mass spectrometry. There was no evidence of any laser-induced products. An upper bound was deduced for the HF + CH2CF2 addition rate constant at 610 K: krlo < 1 X 108 L rnol-' s-I.

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Section: Introductionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH₂CF₂ system

Beck¹,

Burns²

1984

Can. J. Chem.

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“…The acetylene arises from subsequent multiple infrared photon excitation of the vinyl chloride product [2,9], followed by HC1 elimination. The combined vinyl chloride + acetylene yield was within 20%, and frequently within lo%, of the yield of ethylene.…”

Section: Product Identificationmentioning

confidence: 99%

“…Examples of such systems are trans-dl-vinyl chloride (isomerization to cis form versus dehydrohalogenation) [2], cyclopropane (isomerization to propylene versus fragmentation) [3], and ethyl vinyl ether (C-0 cleavage versus cyclic rearrangement) [4]. A problem in interpreting these experiments is that, in general, accurate unimolecular dissociation rates for the various channels are not generally available.…”

Section: Introductionmentioning

confidence: 99%

Infrared photochemistry of cyclobutyl chloride

Francisco

Steinfeld

1981

Int J of Chemical Kinetics

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The decomposition of cyclobutyl chloride following multiple infrared photon excitation has been investigated. The primary photolysis products are butadiene, from elimination of HC1, and ethylene and vinyl chloride, from ring scission. The vinyl chloride undergoes secondary decomposition to acetylene and HC1. In addition to these products, known from thermal VLPP experiments, we also find 1-butene, which may arise from a higher energy C-Cl homolysis channel. Collisions with either reactant molecules or added buffer gas lead to cooling of the laser-produced vibrational energy distributions. The average amount of energy removed per collision is 15-20 kcal/mol for self-collisions and 2-4 kcal/mol with argon.

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“…There have been numerous reported attempts to effect cis-trans isomerization using infrared multiphoton isomerization (8). Early efforts using focused lasers resulted in more fragmentation than isomerization.…”

mentioning

confidence: 99%

Infrared multiphoton isomerization and fragmentation reactions of organic molecules

Lewis¹,

Buechele²,

Teng³

et al. 1982

Pure and Applied Chemistry

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-The tunability of the CO2 molecular gas laser permits selective multiphoton infrared excitation of one isomer in a mixture of isomers. This capability can be exploited to drive isomerization reactions in a contrathermodynamic direction. Examples of such reactions are the trans + cis isomerization of alkenes and the electrocyclic isomerization of butadienes to cyclobutenes. It is also possible to achieve some selectivity in consecutive isomerization reactions (A + B + C) and in competing reactions (A + B ÷ C) via multiphoton infrared excitation. For example, consecutive reactions can be stopped at the intermediate product B in cases where the activation energy for B + C is lower than that for A + B. The product ratio B/C in competing reactions is, in some cases, dependent upon the average vibrational temperature of the reactant A and hence can be altered by changing laser fluence or collisional frequency. In addition, pulsed infrared lasers can be used to create high concentrations of vibrationally excited fragmentation products. We are currently seeking to correlate product vibrational energy distributions with reactant structure and decomposition mechanism. INTRODUCT IONReactions of electronically excited polyatomic organic molecules have occurred on earth since the prebiotic era and have been the subject of scholarly publications since the emergence of the modern chemical literature. All photochemists are familiar with the Stark-Einstein law: electronic excitation occurs upon absorption of a single quantum of light. Under the best of circumstances, the electronically excited molecule can undergo chemical transformation with unit efficiency. Absorption of a single infrared photon produces a vibrationally excited molecule with insuffficient energy to undergo chemical transformation. With the advent of high powered infrared lasers, it has become possible to effect chemical reactions via multiphoton absorption in an intense laser field (1-4). Thus laser technology has spawned a new field of chemistry, infrared photochemistry. From a historical perspective it is interesting to note that the initial investigations of photochemical mechanisms were conducted in the vapor phase (5). Chemical applications of infrared lasers have thus far been limited almost exclusively to the vapor phase. THE CO2 LASERThe commonly used source for infrared laser chemistry is the pulsed CO2 molecular gas laser. The important characteristics of the CO2 laser are (a) high power (ca. 1020 photons/pulse or several gigawatts/cm2 in a focused beam), (b) moderately short pulse duration (< 1 is), and (c) limited tunability from ca. 907 to 992 cm1 and from 1016 to 1092 cm1. Its high power makes the CO2 laser well suited for many technological (welding, cutting, etc.) as well as chemical applications. Thesimplest chemical application of CO2 lasers is the uniform heating of the irradiated volume either by direct absorption 1683

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Infrared photochemistry of halogenated ethylenes

Cited by 79 publications

References 9 publications

Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH₂CF₂ system

Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH₂CF₂ system

Infrared photochemistry of cyclobutyl chloride

Infrared multiphoton isomerization and fragmentation reactions of organic molecules

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Infrared photochemistry of halogenated ethylenes

Cited by 79 publications

References 9 publications

Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH2CF2 system

Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH2CF2 system

Infrared photochemistry of cyclobutyl chloride

Infrared multiphoton isomerization and fragmentation reactions of organic molecules

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Product

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Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH₂CF₂ system

Laser-induced addition of hydrogen fluoride to unsaturated molecules: the HF + CH₂CF₂ system