The Radiolysis of Ethanol: Iv. Deuterated Ethanols in the Liquid and Gas Phases

Abstract

The value of G (-ethanol) in the vapor phase is nearly double that in the liquid phase. Part of the difference appears to be due to the recombination of radicals in liquid cages. Ethanol molecules, on the average, break into s~llaller fragments in the gas than in the liquid phase radiolysis. The isotopic con~positions of the hydroge? produced from various deuterated ethanols are consistent with the suggestion that the reactlon CH,CH?OH+ + CH3CH,OH + CH3CHzOH?+ + CH3CH?O occurs t o a significant extent in the liquid but not in the gas phase. This reaction probably involves the shift of a hydrogen atom along a hydrogen bond. The reaction C?HjOH?+ + e,,~; + C?H50 + H 2 does not occur to an appreciable extent in the liquid phase. I n the liquid phase the relative contributions of the three different groups in the ethanol molecule to hydrogen production are in the order CN2 > OH >> CH3. H similar trend occurs in the gas, although the contributions of the three groups are more nearly equal in this phase. Isotope effects, in the range kn/ku = 2.2-3.9 per bond, occur in the methane formation mechanism. The isotope effects are some\vhat srllaller in the liquid than in the vapor phase and somewhat smaller in the inhibited than in the uninhibited systems. H comparison of product distributions in the liquid and gas radiolyses of several compounds by y-rays and by a-particles indicates that L.E.T. effects can also occur in the gas phase. ISTRODUCTIONI t has been suggested that the reaction [I] CH,CH?OH+ + CHJCM~OH + CH3CH20Me+ + CH3CH20 occurs in the liquid phase radiolysis of ethanol (I). Since this reaction merely involves the shift of a hydrogen atom along a hydrogen bond, it should occur to a smaller extent in the vapor than in the liquid phase. This hypothesis can be tested by irradiating C 2 H 5 0 D and CzD5013 in the liquid and vapor states to determine the contributions of the hydroxyl hydrogen to the product hydrogen in the two phases. I t is expected that the contribution of the hydroxyl hydrogen will be greater in the liquid phase. The present paper reports the results of this test. TO increase the confidence that inay be placed in the results and their interpretation, the isotopic colnposition of the product hydrogen froin CHsCDnOH, CD3CH20H, and CzDBOD is also reported.Ryan et al. (2) have recently observed that reaction [I] does not occur to an appreciable extent in a mass spectrometer, but that the reaction occurs very readily. However, all of the reactions [3]-[5] occurred readily under the salne conditions as those used for the ethanol study, so the situation is not clear.

Mechanism of the reaction of H atoms with methanol

“…The re-formation of methanol via reaction (8) and (11) explains the stoichiometry of 1.8 reported in [9, 101. Abstraction as primary attack (I) followed by abstraction in the reaction of CH,OH/CH,O (1) radicals and H atom addition to form methyl radicals (2) would give a stoichiometry of two.…”

The Radiolysis of Ethyl Mercaptan1

“…Reactions similar to (3) to (5) have been postulated in a mechanism for the radiolysis of ethanol.16 However, in the ethanol system there is evidence that the reaction similar to (3) occurs to a significant extent in the liquid but not in the gas phase. 19 This appears to be due to the fact that the hydrogen bonding present in the liquid phase could not aid the formation of the transition complex I in the gas phase.19…”

Saturn's inner satellites: Ice chemistry and magnetosphere effects

“…For example, the G value for the processing of CH 3 CH 2 OH → CH 3 CHO (in the pure state) is 3.5 molecules/100 eV. G values and chemistry utilized here are from radiolysis experiments of the materials in the liquid or solid phase only, and are from the following references: Basson [1969], Myron and Freeman [1965a, 1965b], Ramaradhya and Freeman [1961], Imamura et al [1963], Hayon and Weiss [1961a, 1961b], Theard and Burton [1963], Silaev et al [1979], McDonnell [1955], McDonnell and Gordon [1955], and McDonnell and Newton [1954]. Ketene chemistry (CH 2 CO and HCCO) is from Boullart et al [1994] and Carl et al [2001].…”