Reaction of Oxygen Atoms With Benzene

Abstract

The reaction of benzene with oxygen atoms produced by mercury photosensitized decomposition of ~litrous oside has been studied in a circulating systern a t roorn temperature. The maill reaction product is a non-volatile material probably largely aldehydic in character. This is tentatively assumed to result from the rearrangetnentand polymerization of the initially for~ned aclduct. Smaller alllou~lts of phenol and carbon monoxide are also formed. The rate of forlllatioll of carbon monoxide decreases with increasing pressure, suggesting an energyrich precursor.Oxygen atoms react with benzene much more slowly than with olefines. At 120" cyclopentene reacts about 150 times more quickly than benzene. 'The activation energy of the reaction of oxygen atoms with benzene has been estimated a t -1.6 to -1.9 kcal/rnole, with a n uncertainty of about 0.7 kcal/mole. INTRODUCTIOSReactions of a nurnber of unsaturated hydrocarbons with oxygen atoms generated by the mercury photosensitized decolnpositio~l of nitro~ls oxide have been studied in some detail in this laboratory, but attention has previously been concelltrated on alkenes and cycloalltenes (1-3). The present investigation is a further stage in these studies and has been u~ldertaltell in an attempt to derive some information on the attack of ground state oxygen atoms on an aronlatic n~~cleus. Unfortunately, the major part of the reaction product, a poly~neric inaterial of low volatility, could not be characterized; only a fraginentary pict~lre of the process has therefore been obtained. This is in sharp contrast to the relativelj-well-understood nlajor feat~ii-cs of the reactions of oxygen atoms with alkenes.Early attempts to obtain approximate valucs oi the rates of reactions of a nulllber of compounds with oxygen atonls (4) led to the co~lclusioll that benzene reacted very rapidly with oxygen atoms. In the present work, however, this reaction is found to be much slower tllall the corresponding reactions of alkenes. I n view of the electrophilic character of oxygen atoms (3), this finding is not ~lnexpectecl.Several worlters (4-7) have iilvestigated the reaction of beilzelle with oxygen atoms generated i l l electrical discharges. Chu, -\i, and O t l~n~e r (8) useel a flow system and generated oxITgell atollls by electrical discharge in illolecular oxygen. They obtained phenol yields of LIP to 13% per pass, in substantial agreement with the previous filldings of Avramenlto and co-workers (7). I-Iolvever, with water vapor instead of oxygen discharge they founcl no detectable amouint of phenol although rlvramenlto et al. clainled yields of up to 27% ~11lder si~llilar conditions.The presence of other reactive species and the need to rnaintaiil relatively low over-all pressures seriousl>~ conlplicate the use of electrical discharges in molecular oxygeil or in water vapor for fundaineiltal studies of the reactions of oxygen ato~lls with organic compouncls. Some of the potential complexities liave beell discussed elsewhere (8) in co~lllectioil with a s t~l d y of th...

Quantum Chemical and RRKM Investigation of the Elementary Channels of the Reaction C6H6 + O (3P)

“…Furthermore, the data were consistent with addition being the product channel, although the products were not directly measured. The most recent work by Ko et al 7 using a method similar to Nicovich et al over a temperature range of 600-1330 K returned Arrhenius parameters and conclusions very similar to those of ref 4. Benzene combustion modelers have employed the addition channel (product ) phenol), 14,15 the abstraction channel (product ) phenyl + OH), 14,15 and the addition/elimination channel (product ) phenoxy + H).…”

Theoretical Reinvestigation of the O(3P) + C6H6 Reaction: Quantum Chemical and Statistical Rate Calculations

“…14 The Lowest-Lying Singlet Surface. As mentioned above, almost all experimental studies 12,[18][19][20][21] show singlet phenol to be one of most important products for the title reaction. In addition, benzene oxide was experimentally detected earlier 18 and very recently cyclohexadienone, butadienyl ketene, and benzene oxide have been observed in an argon matrix study.…”

“…Figures 10 and 11 also show that the products c-C 5 H 6 + CO, phenol, and benzene oxide/oxepin are major, at least in some conditions, while the products phenoxy radical + H, c-C 6 H 4 + H 2 O, the ketone S3 and BDK S8 are always minor. These results are in agreement with earlier experimental observations for key products such as phenol and CO. [19][20][21] As can be seen, the fractions of the various products depend in a complex way on T and P. In general, an increase of temperature enhances the yields of c-C 5 H 6 + CO, phenoxy radical + H, and c-C 6 H 4 + H 2 O. On the other hand, increasing the pressure will reduce the yields of c-C 5 H 6 + CO, phenoxy radical + H, and c-C 6 H 4 + H 2 O, but increase those of phenol and benzene oxide/oxepin.…”

Mechanisms of Photochemical Air Pollution

“…For example, following the initial addition of O(3P) to the benzene ringrs6] [reaction (32)], ring opening may occur according to reaction (33)[*']'. Subsequent reactions of the unsaturated diradical may then produce the nonvolatile products [86]. Alternatively, the following Scheme (34) has been proposed[861 to account for the observed products :…”