Ethoxy Radical Yield in the System C2D5OH plus F(2P) plus F2 at P = 1 Torr and T = 223-423 K

Abstract

A discharge flow reactor with mass spectrometric detection has been used to determine the fractional yield of ethoxy, Y(EtO), from the reaction of F(2P) with C~D S O H . The chemical titration method that was used depends only upon the occurrence of the fast chain reaction, F2 + C2D40H -C2D40H + F, and the ability to measure relative concentrations of ethoxy radical. Ethoxy concentration was proportional to the detected ion count signal a t m/z 50.[Ethoxy] was titrated to an asymptote with a large excess of F2. The titration removes hydroxyethyl radicals and regenerates F so that, a t the asymptote, each F initially present will have formed one ethoxy radical. The experimental value of Y(Et0) is the ratio of the m / z 50 signal in the absence of F2 to the signal in the presence of F2. The measured values of Y(Et0) f ( l a ) are 0.62 f 0.08 a t 223 K, 0.55 f 0.06 a t 300 K, and 0.39 f 0.02 a t 423 K. An Arrhenius analysis of these data implies that the average activation energy for abstraction a t a C-D bond is about 1 kcal/mol larger than that for abstraction at the 0-H bond. The activation energy for attack a t 0-H is likely to be near zero. Allowing F(2P) to react with large excesses of ethanol and F2 provides a good clean source of ethoxy radical.

H Abstraction Channels in the Crossed-Beam Reaction of F + 1-Propanol, 1-Butene and 1-Hexene by DC Slice Imaging

“…One thing to mention is that both reactions have similar collision energies of about 10 kcal mol –1 , and in both systems, only secondary abstraction products were detected . As for alkane reactions the different collision energies can tell the relative importance of the stripping mechanism, it is very likely that the ⟨ E T *⟩ difference between n -butane and 1-propanol come from C–O and O–H interference, which is in consistent with the results of the kinetic studies. , The energy release of α-H abstraction is 5 kcal mol –1 more than β-H abstraction, while their H numbers are 1:2; these two factors may compete with each other to determine the final branching. According to the kinetic studies on the branching ratios of F with alcohols, the O–H group abstraction is more favored over the attack on C–H groups, even though for propanol these H sites are in the ratio is 1:7.…”

“…44 As for alkane reactions the different collision energies can tell the relative importance of the stripping mechanism, it is very likely that the ⟨E T *⟩ difference between n-butane and 1-propanol come from C−O and O−H interference, which is in consistent with the results of the kinetic studies. 15,22 The energy release of α-H abstraction is 5 kcal mol −1 more than β-H abstraction, while their H numbers are 1:2; these two factors may compete with each other to determine the final branching. According to the kinetic studies on the branching ratios of F with alcohols, a The latter is given along with the fraction of collision energy appearing in translation for the indicated center-of-mass scattering regions.…”

“…Several measurements on the alkoxy yield from reactions of F with normal and deuterated ethanols and propanols presented similar alkoxy product fractions. 15,22,23 The fraction yielding ethoxy radical is reported to be 0.5 although alkyl hydrogen abstraction is also energetically favored. The probability of attack on the C−H group was found to be five times less than attack on the O−H group for the reactions of F atoms with alcohols.…”

“…The CH 3 OH + F reaction system was previsously studied by means of HF or radical emission spectra. − Reaction enthalpies for H abstraction in methanol are: …”

Pressure and Temperature Dependence of Ethyl Nitrate Formation in the C2H5O2 + NO Reaction

“…The total rate constant of this fast reaction is k 9 ) 1.2 × 10 -10 cm 3 molecule -1 s -1 . This source was recommended by Bogan and Nesbitt, 19 who determined the branching fraction of C 2 H 5 O formation γ ) k 9a /k 9 ) 55 ( 4%. When NO 2 was introduced into the reactor ([NO 2 ] ≈ 1 × 10 13 molecules cm -3 ), ethyl nitrate was formed via addition reaction 4:…”