RADIATION CHEMISTRY OF CYCLOHEXANE: I. ISOTOPIC COMPOSITION OF HYDROGEN EVOLVED FROM MIXTURES OF C6D12 AND C6H12

Dyne, P. J.; Jenkinson, W. M.

doi:10.1139/v60-076

Cited by 24 publications

(7 citation statements)

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“…Reaction (9) is known to occur in alkanes [40]. Ion-molecule reactions of the type (10) or (11) have been suggested to explain H 2 production and dimer formation in hexane radiolysis by KEVAN and LIBBY [41].…”

Section: Discussionmentioning

confidence: 99%

Inter- and Intramolecular Energy Transfer in Gammaradiolysis of n-Alkylbenzenes

Zeman¹,

Heusinger²

1967

Radiochimica Acta

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Hydrogen production in y-irradiated ii-alkylbenzenes (toluene to heptadecylbenzene), in isomeric η -alkylbenzenes and Ji-alkylbenzenes-d 5 was investigated. Radicals formed at 77 °K were identified by EPR-spectroscopy and their G-values measured. A mechanism for the formation of hydrogen, based on ion-molecule reactions and hot atom reactions, is proposed. The low G(H 2 ) und G(R) values of the various ra-alkylbenzenes indicate that the phenyl group protects the alkyl group, with respect to hydrogen and radical formation. Energy transfer was suggested to explain the results. A MARKOV chain approach shows that energy transfer from the aliphatic chain to the phenyl group is 13 times as probable as the dissociation of a C-Η bond and the desactivation of the excited state involved. To separate inter-and intramolecular energy transfer, a similar investigation with alkane/benzene mixtures was carried out. The probability for energy transfer from the alkane chain to the benzene molecule was found to be 10 times as probable as the two other reactions. The results suggest that in n-alkylbenzenes besides intermolecular transfer also intramolecular transfer takes place, with comparable efficiency.Zusammenfassung DieWasserstoff bildung in y-bestrahlten ra-Alkylbenzolen (Toluol bis Heptadecylbenzol), in isomeren w-Alkylbenzolen und w-Alkylbenzolen-d 6 , wurde untersucht. Die bei 77 °K gebildeten Radikale wurden EPRspektroskopisch identifiziert und ihre G-Werte gemessen. Die Untersuchungen zeigen, daß Wasserstoff über Ionen-Molekülreaktionen und Abstraktionsreaktionen heißer Η-Atome gebildet wird. Die G-Werte für die Wasserstoff-und Radikalbildung sind stets kleiner als nach der Additivitätsregel berechnet. Dies zeigt: die Phenylgruppe vermag die Alkylgruppe zu schützen. Wir machen Energieübertragung für diesen Schutz verantwortlich. Es wurde gezeigt, daß sich die Vorgänge bei der Energieübertragung als eine MARKOV Kette von Ereignissen darstellen lassen. Aus dieser Behandlung ergibt sich, daß Energieübertragung von der aliphatischen Kette in den Phenylkern dreizehnmal häufiger ist als die Dissoziation einer C-Η-Bindung und Desaktivierung des angeregten Zustande in der Kette. Um zu klären, ob die Energieübertragung intra-oder intermolekular erfolgt, wurden analoge Untersuchungen an Alkan/Benzolmischungen durchgeführt. Der Energieübergang von der aliphatischen Kette ist in diesem Fall zehnmal so häufig als die beiden anderen Reaktionen. In w-Alkylbenzolen findet also neben einer intermolekularen Energieübertragung eine vergleichbare intramolekulare Über-tragung statt. ResumeOn examine la production d'hydrogene dans des «.-alkyl-benzenes (toluene a heptadecylbenzene) soumis aux radiations γ ainsi que dans les isomeres »-alcyl-benzenes et »-alkyl-benzenes-d 5 .Les radicaux formes vers 77 °K ont ete identifies par spectroscopie EPR et les rendements G mesures. On propose un mecanisme de formation de l'hydrogene par reactions ions-molecules et reactions d'atomes chauds. Les valeurs faibles des G trouves pour la formation de l'hydro...

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Section: Discussionmentioning

confidence: 99%

Inter- and Intramolecular Energy Transfer in Gammaradiolysis of n-Alkylbenzenes

Zeman¹,

Heusinger²

1967

Radiochimica Acta

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“…1. In the present experiments, however, the 2-ml samples were irradiated for 2 hours a t a dose rate of --2.2X1OZ2 ev/lt hr.…”

Section: Introductionmentioning

confidence: 86%

“…These results are shown in Table I. Values of Gl(D), the unimolecular yield, were obtained using the graphical extrapolation described in (1). Values of g(HD),4 the yield of H D per unit mole fraction of C6D12, were obtained from the slope of the linear plot of G(HD) vs. mole fraction C6D12.…”

Section: Introductionmentioning

confidence: 99%

RADIATION CHEMISTRY OF CYCLOHEXANE: III. EFFECT OF BENZENE AND IODINE ON THE ISOTOPIC COMPOSITION OF RADIOLYTIC HYDROGEN FROM C₆D₁₂–C₆H₁₂ MIXTURES

Dyne¹,

Jenkinson²

1961

Can. J. Chem.

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The isotopic composition of hydrogen evolved in the radiolysis of C B D~T C B H~P mixtures has been measured in the presence of various amounts of benzene and iodine. The yield of the uni~nolecular decomposition and the specihc yield of the bimolecular reaction are reduced in approxin~ately the same proportion as the yield of total hydrogen. I t is concluded that (i) iodine and benzene interact to a comparable extent with both ~~nimolecular and bimolecular decon~position modes, (ii) it is probable that neither of these additives act by scavenging, and (iii) it is probable that they act by quenching a common precursor of the two decomposition modes. INTRODUCTIONWe have shown from measurements of the isotopic composition of hydrogen produced in the radiolysis of C6D12-C6H12 ~~l i x t u r e s(1) that part of the hydrogen is formed in a bimolecular processS n + C G I I~V -+ 1-12 + P PI where the atoms in the H z molecule come fro111 two different cyclohexane molecules, and part is formed in a unimolecular process CGH12 ---3 t I ? + P yield Gl(H)[ 3 I where both hydrogen atoms come from the same cyclohexane molecule. The symbol P represents any product or residue and XE is the reactive intermediate in the biinolecular process.The specific yield of the cleco~~~positionin a large excess of CGI-112 WilS show~l to be 0.25 molecules/100 ev absorbed in the C6DlZ. However, the yield of reaction [3] in pure CGI-112 may amount t o between 25% (2) and nearly 50% (3) of the total yield. I t is conceivable that this large "isotope effect" expresses variations in Gl(D) and Gl(H) with the isotopic con~position of the solvent due to some type of energy transfer or charge transfer effect. In the experinients described in this paper we used the yield of D2 fro111 CGDlZ as an "i~ldicator" of the efficiency of unimolecular processes in benzene and iodine solutions in cyclohexane. We also showed (1) that Gl(D), the yield of reaction [4], was reduced by biphenyl, and slightly reduced by iodine. We concluded that biphenyl could act as a quenchi~lg agent2 on the excited precursors involved in the unilllolecular decomposition.In this paper we describe a series of measurements of the isotopic composition of hydrogen evolved in the radiolysis of CGD12-C61-112 mixtures in the presence of varying amounts of benzene and iodine. We find that, for both these substances, G1(D) is reduced in approxi~llately the same proportioil as the total hydrogen yield, and we infer that the ~~nimolecular and bimolecular decolllpositio~ls are quenched t o approxilllately the salne extent by these substances. Burton and Chang (4)

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“…(12) to the vapor phase radiolysis of cyclohexane using benzene as a scavenger. We applied this same technique to the cyclohexane radiolysis, using N 2 0 and SF, as specific electron scavengers, to see if electron scavengers had any effect on the first order hydrogen yield.…”

Section: Introductionmentioning

confidence: 99%

γ-Radiolysis of cyclohexane with electron scavengers. VI. N₂O and SF₆ as electron scavengers in the vapor phase

Sagert¹,

Robinson²,

Blair³

1968

Can. J. Chem.

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The γ-radiolysis of cyclohexane has been examined in the vapor phase using N2O and SF6 as electron scavengers. Both N2O and SF6 reduce the hydrogen yield from 4.6 to 3.0 G units, indicating that 3.0 G units of hydrogen have neutral species as precursors, while 1.6 G units have electrons as precursors.Radiolysis of cyclohexane vapor with more than 2% N2O produces 10.4 G units of cyclohexene and 11.5 of nitrogen. Carbon dioxide reduces both these yields; the extrapolated value of G(N2) is equal to G(electrons) at infinite CO2 concentration. Thus O− is likely a precursor of that part of the nitrogen yield in excess of G(electrons), and of the cyclohexene yield associated with this nitrogen yield.The first order molecular detachment of hydrogen is unaffected by electron scavengers, showing that most of this first order yield has neutral precursors. The implications for Dyne's general mechanism of hydrocarbon radiolysis are discussed.

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RADIATION CHEMISTRY OF CYCLOHEXANE: I. ISOTOPIC COMPOSITION OF HYDROGEN EVOLVED FROM MIXTURES OF C₆D₁₂ AND C₆H₁₂

Cited by 24 publications

References 5 publications

Inter- and Intramolecular Energy Transfer in Gammaradiolysis of n-Alkylbenzenes

Inter- and Intramolecular Energy Transfer in Gammaradiolysis of n-Alkylbenzenes

RADIATION CHEMISTRY OF CYCLOHEXANE: III. EFFECT OF BENZENE AND IODINE ON THE ISOTOPIC COMPOSITION OF RADIOLYTIC HYDROGEN FROM C₆D₁₂–C₆H₁₂ MIXTURES

γ-Radiolysis of cyclohexane with electron scavengers. VI. N₂O and SF₆ as electron scavengers in the vapor phase

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RADIATION CHEMISTRY OF CYCLOHEXANE: I. ISOTOPIC COMPOSITION OF HYDROGEN EVOLVED FROM MIXTURES OF C6D12 AND C6H12

Cited by 24 publications

References 5 publications

Inter- and Intramolecular Energy Transfer in Gammaradiolysis of n-Alkylbenzenes

Inter- and Intramolecular Energy Transfer in Gammaradiolysis of n-Alkylbenzenes

RADIATION CHEMISTRY OF CYCLOHEXANE: III. EFFECT OF BENZENE AND IODINE ON THE ISOTOPIC COMPOSITION OF RADIOLYTIC HYDROGEN FROM C6D12–C6H12 MIXTURES

γ-Radiolysis of cyclohexane with electron scavengers. VI. N2O and SF6 as electron scavengers in the vapor phase

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RADIATION CHEMISTRY OF CYCLOHEXANE: I. ISOTOPIC COMPOSITION OF HYDROGEN EVOLVED FROM MIXTURES OF C₆D₁₂ AND C₆H₁₂

RADIATION CHEMISTRY OF CYCLOHEXANE: III. EFFECT OF BENZENE AND IODINE ON THE ISOTOPIC COMPOSITION OF RADIOLYTIC HYDROGEN FROM C₆D₁₂–C₆H₁₂ MIXTURES

γ-Radiolysis of cyclohexane with electron scavengers. VI. N₂O and SF₆ as electron scavengers in the vapor phase