Reactions of energetic fluorine-18 atoms with tetrafluoroethylene

Smail, Thomas; Miller, George E.; Rowland, F. S.

doi:10.1021/j100713a006

Cited by 16 publications

(8 citation statements)

References 5 publications

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“…The prime source of this discrepancy resides in the question of volatile yields not determined by radio gas chromatographic analysis. 6 Our summed yields of CH18F==CII2 plus C2H618F amount to only about 65% of the total 18F formed, and we attribute ~30% to formation of H1SF by reaction with C2H4.…”

Section: Resultsmentioning

confidence: 68%

“…recent studies with crossed beams of F atoms (from thermal dissociation of F2) and C2H4 or C2D4 have convincingly shown that the substitution of F for H (or D) proceeds through a long-lived intermediate, C2H4F (or C2D4F). 6 The relative kinetic energy of F atoms and ethylene molecules averaged only 1.98 and 1.94 kcal/ mol, respectively, with C2H4 and C2D4 in these experiments. We have recently reported the results of some experiments on fluorine atom additions to olefins and acetylene, using 18F atoms generated at tracer levels by the nuclear reaction 19F(n,2n)18F,6-8 and obtained some information on reactions with ethylene in the process.…”

Section: Introductionmentioning

confidence: 68%

“…At any HI/C2H4 ratio 5:0.1, sufficient HI is present to capture all of the stabilized CH218FCH2 radicals. As the ratio of HI/C2H4 is increased, however, a smaller percentage of 18F atoms are captured by C2H4 because of competition with reaction 1 by reaction 6.-2 18F + HI -> H18F + I (6) The data of Table I can be plotted in the usual manner for chemically activated species, i.e., decomposition/ stabilization (D/S) vs. reciprocal pressure, giving a good straight line for the CH18F==CH2/CH3CH218F ratio as expected wdien the sources for both are CH218FCH2* radicals with reasonably monoenergetic excitation. Our HI-scavenger data are in good agreement with the CH18F=CH2/CH218FCH2I ratios measured earlier in the presence of I2 scavenger by Colebourne, Todd, and Wolfgang,18 as shown in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

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Reactions of fluorine-18 atoms with ethylene

Williams¹,

Rowland²

1972

J. Phys. Chem.

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Publication costs assisted by Division of Research, U. S. Atomic Energy Commission Energetic 18F atoms formed by the 19F(n,2n) 1SF nuclear reaction can undergo both hot and thermal addition reactions with ethylene to form excited CH218FCH2* radicals. The hot reactions of 18F can be almost entirely suppressed by moderation with SF6 or CF4, and the excited CH218FCH2* radicals exhibit normal stabilizationdecomposition (to CH18F=CH2 + H) behavior vs. pressure for monoenergetically excited radicals. The stabilized radicals are observed as CH3CH218F after reaction with scavenger HI. The half-stabilization pressures for SF« and CF4 are 80 and 135 Torr, respectively, and are essentially unchanged for moderator fractions >0.75. The difference in half-stabilization pressures indicates that SF6 is more efficient, per molecule. in removing the excitation energy of CH2,SFCH2* radicals. In less-moderated systems, hot reactions are also observed: (a) the formation of CH18F=CH2 by a more energetic route; (b) the formation of CH18F from secondary decomposition of CH18F=CH2; and (c) the formation of CH218F by decomposition of CH2-18FCH2*. The rupture of the C-C bond in CH218FCH2* probably occurs predominantly after capture of 18F at high-impact parameters with consequent high-angular momentum in the excited radical. Similarly, substitution of 1SF/H at high-impact parameters is postulated to lead to the C=C bond rupture in CH18F=CH2*.

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Section: Resultsmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

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Reactions of fluorine-18 atoms with ethylene

Williams¹,

Rowland²

1972

J. Phys. Chem.

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“…carried out which unambiguously involve the reactions of atomic fluorine with aromatic systems despite the considerable interest in such reactions.2 345However, radioactive 1SF atoms (tv, = 110 min) can be produced by various nuclear reactions, including the 19F(n,2n)18F reaction with fast neutrons, and these atoms can be brought to thermal energies without bond formation by multiple collisions with suitable inert moderators. [3][4][5][6][7][8][9][10][11][12][13][14][15] In the last several years, research in this laboratory has utilized such thermal 18F atoms for reaction studies with olefins,6•7•9•10 acetylene,8 various RH compounds,11 and a variety of inorganic species.12•13…”

Section: General Considerationsmentioning

confidence: 99%

Spectroscopic studies of some laser dyes

Pavlopoulos¹,

Hammond²

1974

J. Am. Chem. Soc.

107

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The infrared spectrum of 11 shows characteristic peaks at 3250 cm-1 2(N-H) and 1720 (cm"1 (0=0); nmr (CD2C12) 1.2 ppm (6 H), multiple! 2.2 (4 ), 0.85 ppm (4 H).1,5,7-Trimethylnorpseudopelletierine A'-Oxyl, 12, To a solution of 1 g of 1,5,7-trimethylnorpseudopelletierine in 10 ml of water was added 10 mg of phosphotungstic acid and 1.2 ml of hydrogen peroxide. The reaction mixture was cooled in an ice bath. After

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“…However, from radiolysis experiments with CF 3 -CF 3[19] it is known that dissociation of a C-F bond is also possible. For excited CF 2 18 F-CF 3 formed by a 18 F-for-F reaction in CF 3 -CF 3 or I8 F-for-H reaction in CF 3 -CF 2 H, this would result in labeled CF 3 -CF 2 -radicals.These C 2 F 5 · radicals can stabilize by Η-abstraction from H 2 S, decomposition to tetrafluoroethene, or by a C-Cbond scission (scheme 4)[25], Part of the CF 18 F=CF 2 observed in CF 3 -CF 2 H and all the CF ,8 F=CF 2 in CF 3 -CF 3 could thus originate from these 18 F-pentafluoroethyl radicals; however, one should keep in mind that the main channel of formation of (' 8 F)CF 3 -CF 2 -radicals in CF 3 -CF 3 is the 18 F-for-2F replacement reaction.at 10 s Pa is < 0.2%) and very low in CF 3 -CH 3 (at 10 s Pa the yield is about 0.2%), is more important in the higher fluorinated ethanes; for CF3 -CF 2 H and CF 3 -CF 3 yields of about 0.6% at « 5 χ IO 6 Pa are found. The 18 Ffor-CF 3 reaction in CF 3 -CF 2 H yielding CF 2 18 FH could not be analysed because no distinction could be made between CF 2 18 FH formed by this reaction and that formed by C-C scission of excited 18 F-fluoroalkanes.…”

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confidence: 99%