Kinetics of the dehydrofluorination of vinyl fluoride in a single-pulse shock tube

Simmie, John M.; Quiring, W. J.; Tschuikow‐Roux, E.

doi:10.1021/j100700a005

Cited by 54 publications

(22 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…20 The HX/X branching ratio changes dramatically from vinyl fluoride to vinyl iodide. For vinyl fluoride, high-temperature thermal decomposition, 21 infrared multi-photon dissociation (IRMPD) 22 and UV photodissociation 10,23 produce only HF + HCCH/H 2 CC. Both atomic and molecular dissociation channels occur in vinyl chloride 19,24 and vinyl bromide 5 UV photodissociation.…”

Section: Introductionmentioning

confidence: 99%

Ultraviolet photodissociation of vinyl iodide: understanding the halogen dependence of photodissociation mechanisms in vinyl halides

Zou

Strecker

Ramirez-Serrano

et al. 2008

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The photodissociation of vinyl iodide has been investigated at several wavelengths between 193 and 266 nm using three techniques: time-resolved Fourier transform emission spectroscopy, multiple pass laser absorption spectroscopy, and velocity-mapped ion imaging. The only dissociation channel observed is C-I bond cleavage to produce C2H3 (nu, N) + I (2P(J)) at all wavelengths investigated. Unlike photodissociation of other vinyl halides (C2H3X, X = F, Cl, Br), in which the HX product channel is significant, no HI elimination is observed. The angular and translational energy distributions of I atoms indicate that atomic products arise solely from dissociation on excited states with negligible contribution from internal conversion to the ground state. We derive an upper limit on the C-I bond strength of D0(C2H3-I) < or = 65 kcal mol(-1). The ground-state potential-energy surface of vinyl iodide is explored by ab initio calculations. We present a model in which the highest occupied molecular orbital in vinyl halides has increasing X(np) non-bonding character with increasing halogen mass. This change leads to reduced torsional force around the C-C bond in the excited state. Because the ground-state energy is highest when the CH2 plane is perpendicular to the CHX plane, a reduced torsional force in the excited state correlates with a lower rate for internal conversion compared to excited-state C-X bond fission. This model explains the gradual change in photodissociation mechanisms of vinyl halides from the dominance of internal conversion in vinyl fluoride to the dominance of excited-state dissociation in vinyl iodide.

show abstract

Section: Introductionmentioning

confidence: 99%

Ultraviolet photodissociation of vinyl iodide: understanding the halogen dependence of photodissociation mechanisms in vinyl halides

Zou

Strecker

Ramirez-Serrano

et al. 2008

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…While part of the difference2 may be ascribed as due to the higher reaction path degeneracy, g = 9, and lower barrier to internal rotation in CF3CH3 (V = 3.5 kcal/mole [16,25]), it cannot account for a factor of -20. For example, within the same degree of approximation the model of O'Neal and Benson would predict roughly a frequency factor ratio of (17) Al6/A2 = (g16/g2) exp [ -( s h ( 1 6 ) -sh(P))/R1 = 4…”

Section: )/Rt]mentioning

confidence: 96%

The Competitive dehydrohalogenation of 1,1,1‐trifluoro‐2‐chloroethane in reflected shock waves

Millward

Tschuikow‐Roux

1972

Int J of Chemical Kinetics

View full text Add to dashboard Cite

The thermal decomposition of 1,1,1 -trifluoro-2-chloroethane has been investigated in the single-pulse shock tube between 11 20" and 1300°K at total reflected shock pressures from -2610 to 3350 torr. Under these conditions, the major reaction is the a,a-elimination of hydrogen chloride, CF,CH&I A CFZCHF + HCI with log (k?, sec-l) = 13.3 f 0.4 -(65.5 f 2.2 kca1)/2.303RT C F 3 C H 2 C l A CFZCHCl + H F The decomposition also involves the slower a,@-elimination of hydrogen fluoride, with the first-order rate constant given by log (k?, sec-I) = 12.7 f 0.5 -(67.6 f 2.7 kca1)/2.303RT At temperatures above 1270"K, two additional minor products were observed. These were identified as CFZCFCI and CF3CHC12 and suggest C-Cl rupture as a third reaction channel leading to complicated kinetics.

show abstract

“…The energy available to the products is -123 kcal/mol [12,13]. Since there is very little C2Hz formed, most of the vibrationally excited CH2CHF molecules that are produced as a result of a rearrangement of CH3CF* must have energies less than 71 kcal/mol, the activation energy for H F elimination from CH2CHF [15]. Therefore the FCl may wrll appear as small yields of F and C1 atoms in the system, whether FCl is initially produced by C Y ,~ elimination or by a two-atom expulsion process.…”

Section: (4)mentioning

confidence: 99%

Photolysis of 1,1,1‐difluorochloroethane (Freon 142) at 147 nm

Ichimura

Kirk

Tschuikow‐Roux

1977

Int J of Chemical Kinetics

View full text Add to dashboard Cite

Abstractl,l,l-l~ifluorochloroethane (Freon 142) was photolyzed a t 147 nm in the pressure range of 3.6-20.6 torr. The effects of added NO, €€& and CF, were investigated. The extinction coefficient a t 147 nm and 296°K was determined to be 64 f 8 atm-' . cm-*.The molecule photodecomposes largely by a,@ elimination of HC1 to give 1,l-difluoroethylene (+ = 0.74 f 0.06). There is no observable elimination of HF, but there is strong evidence for the elimination of the elements of FC1 though the relative importance of this process is minor, as are contributions from carbon-carbon and carbon-halogen bond fission.The 1,l-difluoroethylene formed is undoubtedly vibratonally excited and is the source of a pressure-dependent small yield of fluoroacetylene. Over the pressure range studied there is no evidence that the major primary process itself is affected by changes in total pressure as is the case in the 147-nm photolysis of ethyl chloride.

show abstract

Kinetics of the dehydrofluorination of vinyl fluoride in a single-pulse shock tube

Cited by 54 publications

References 4 publications

Ultraviolet photodissociation of vinyl iodide: understanding the halogen dependence of photodissociation mechanisms in vinyl halides

Ultraviolet photodissociation of vinyl iodide: understanding the halogen dependence of photodissociation mechanisms in vinyl halides

The Competitive dehydrohalogenation of 1,1,1‐trifluoro‐2‐chloroethane in reflected shock waves

Photolysis of 1,1,1‐difluorochloroethane (Freon 142) at 147 nm

Contact Info

Product

Resources

About