γ-Radiolysis of cyclohexane with electron scavengers. VI. N 2 O and SF 6 as electron scavengers in the vapor phase

1969

Mittcilung')Summary. N,O has the following cffects on the radiolysis of light and heavy hexane: I t decreases the bimolecular part of the hydrogen production. A corresponding N,-production amounts to the double of this decrease. The speed of competition Is very much faster at higher temperature. The amount of C-C-bond split yiclding alkyl radicals is decreased but not suppressed. The initial amount of hexyl radicals fornicd is not changed and shows no isotope effect, whereas an additional production of these radicals shows such an effect. They are probably formed by the abstraction by OH-radicals that are products of the neutralization reaction of N,O-with the hexyl cation. This additional amount contributes mainly t o the 3-hexyl-isomer. The part of the additional hexene formation that exceeds the amount produced by disproportionation from hexyl radicals is formed in a unimolecular process yielding water as the second product. This is a main product, hexanols and hexanones have not been found. A partial product balance involving hydrogen, hexyl and hexene is presented. The disproportionation/combination ratio for hexyl radicals is according t o this balance 0.75. Ein1eitung.-Seit den grundlegenden Untersuchungen von SCHOLES & SIMIC [2]uber Stickoxidul als Elektronenfanger in radiolytischen Systemen erfreut sich diese Substanz steigender Beliebtheit. Dies ist wohl darauf zuruckzufuhren, dass auf Grund der bisherigen Erfal-irungen angenommen werden darf, dass N,O im untersuchten Konzentrationsbereich nur als Elektronenakzeptor wirkt und dass die Folgereaktionen meistens das Produktenspektrum der Radiolyse niclit sehr komplizieren. Wenn auch angenommen werden darf, dass N,O die negative Ladung einfangt, so herrschen uber das weitere Schicksal der negativen Species einige Kontroversen [3] [4] 151 [6]. Die vorwiegende Zahl der Untersuchungen von Kohlenwasserstoff-Stickoxidul-Systemen beschrankt sich hauptsachlich auf Cyclohexan. Der wesentliche Grund hiefur mag sein, dass die radiolytischen Hauptprodukte in diesem I-osungsmittel einfach zu bestimmen sind. Dies hat aber den Nachteil, dass es schwierig ist, aus der h d e r u n g der Produktbildung auf einen speziellen Mechanismus zu schliessen. Hexan erlaubt infolge der Vielfalt seiner Produkte ein besseres Abwagen verschiedener Reaktionshypothesen, ausserdem gestattet das breitere Temperaturintervall seiner flussigen Phase ein besseres Erfassen der I'emperaturabhangjgkeit. Deshalb berichten wir irn folgenden uber einige Untcrsucliungeri im Hexan-N,O-System in flussiger Phase. 2, __ ~~_ _ _~Stickstoffoxidul wurdc uns freundlicherweise von der Firma SOCSIL in Kcnens zur Vcrfugung gestellt, wofur wir auch an dicser Stelle herzlich danken inochten.

unclassified

Strahlungschemie von Kohlenwasserstoffen. 17. Mitteilung. Hexan‐NO

Menger¹,

1969

Strahlungschemie von Kohlenwasserstoffen. 18. Mitteilung. Hexan‐N₂O

Menger¹,

1969

N2O has the following effects on the radiolysis of light and heavy hexane: It decreases the bimolecular part of the hydrogen production. A corresponding N2‐production amounts to the double of this decrease. The speed of competition is very much faster at higher temperature. The amount of CC bond split yielding alkyl radicals is decreased but not suppressed. The initial amount of hexyl radicals formed is not changed and shows no isotope effect, whereas an additional production of these radicals shows such an effect. They are probably formed by the abstraction by OH‐radicals that are products of the neutralization reaction of N2O− with the hexyl cation. This additional amount contributes mainly to the 3‐hexyl‐isomer. The part of the additional hexene formation that exceeds the amount produced by disproportionation from hexyl radicals is formed in a unimolecular process yielding water as the second product. This is a main product, hexanols and hexanones have not been found. A partial product balance involving hydrogen, hexyl and hexene is presented. The disproportionation/combination ratio for hexyl radicals is according to this balance 0.75.

Effect of Pressure in the Gamma Radiolysis of Cyclohexane in the Vapor Phase

Milon¹,

1974

721than about six or seven carbon atoms, the randomisation of hydrogen atoms over the whole chain is unimportant but the elimination of olefins proceeds by complicated reaction steps not yet known. We thus think that, in its present state, the validity of the quasi-equilibrium theory for the prediction of the fragmentation pattern of alkyl radical ions is doubtful.We would like to express our thanks to Mr. G. Philippossian for his many hints on synthesis and to the Swiss National Foundation for the Encouragement of Research for a grant.