1- Butylbenzene, oxidation

Pheny 1-3-pheny 1 imino-3-// -indole N -oxide (an indolic nitrone) reacts with triethyl and triisopropyl phosphite in refluxing xylene and fert-butylbenzene to give 2-phenylimino-3// -indole (indolenine) in very good yield (505). 

It is proposed that 32 reacts from its nn excited state by the nitro-to-nitrite (33) inversion followed by nitrite homolysis, when the naphthoxy radical must diffuse away from the cages to obtain the dimerization intermediate 35. However, the source of oxidizing agents is not identified. In comparison, o-nitro-ferf-butylbenzenes 37 are excited to undergo intramolecular H-atom transfer and cyclization to give indol-IV-oxides 40 (equation 34)38. The discrepancy may arise from the nature of the excited state, e.g. that of 37 may react from its njr state. 

In the examples above, one or both of the reaction centers are already attached to the metal center. In many cases, the reactants are free before reaction occurs. If a metal ion or complex is to promote reaction between A and B, it is obvious that at least one species must coordinate to the metal for an effect. It is far from obvious whether both A and B enter the coordination sphere of the metal in a particular instance. A number of metal-oxygen complexes can oxygenate a variety of substrates (SOj, CO, NO, NO2, phosphines) in mild conditions. Probably the substrate and O2 are present in the coordination sphere of the metal during these so-called autoxidations. In the reaction of oxygen with transition metal phosphine complexes, oxidation of metal, of phosphine or of both, may result. The initial rate of reaction of O2 with Co(Et3P)2Cl2 in tertiary butylbenzene. 

Phenyl-2-methylpropane, see sec-Butylbenzene 4-Phenylnitrobenzene, see 4-Nitrobiphenyl p-Phenylnitrobenzene, see 4-Nitrobiphenyl Phenyl oxide, see Phenyl ether... 

In another paper from the Jackson Laboratories of the du Pont Company (Calcott et al., 34) there is reported a repetition of some of the reactions of Simons and Archer, as well as additional ones. Mono-, di-, and 1,2,4,5 tetraisopropylbenzene were obtained from propylene and benzene both l -chloro-i-butylbenzene and di-(l/-chloro)-d-butylben-zene were obtained from 3-chloro-2-methyl-propene-l and benzene p-f-butyltoluene and di-i-butyltoluene were obtained from diisobutylene and toluene tetraisopropylnaphthalene was obtained from propylene and naphthalene naphthyl-stearic acid was obtained from oleic acid and naphthalene mixed isopropyltetrahydronaphthalene was obtained from propylene and tetrahydronaphthalene 2,4,6-triisopropylphenol was obtained from propylene and phenol a mixture of monoisopropylated m-cresols was obtained from propylene and wi-cresol and di-(s-hexyl)-diphenyl oxide was obtained from hexene-3 and diphenyl oxide. 

Butadiene has been co-oxidized with a number of aralkyl hydrocarbons and cyclic olefins. The order of increasing reactivity toward butadieneperoxy radicals (X—02—C H602) is cumene, sec-butylbenzene < cyclooctene < cyclohexene... 

Tables I and II include data for the co-oxidations of styrene and butadiene in chlorobenzene and ferf-butylbenzene solutions, as well as with no added solvent. These solvents were chosen because the rate of oxidation of cyclohexene varies significantly in them at the the same rate of initiation (6). There is a variation in the over-all rate of oxidation under these solvent conditions, but there appears to be no significant difference in the measured ra and rb (Table II). If the solvent does affect the propagation reaction in autoxidation reactions, it affects the competing steps to the same degree.

Let us now consider what we mean by the reactivity of a hydrocarbon in autoxidation. One measure is how fast it oxidizes by itself at unit concentration and unit rate of initiation. (Rates of thermal oxidation at unknown rates of initiation are not useful enough to be considered.) The first two columns of figures in Table VII give such comparisons in terms of kp/(2kt)l/l at 30° and 60°C. and determine the order in which hydrocarbons are listed in the table. The results of Ingold and Sajus agree fairly well the orders of reactivity are identical except for a trivial difference with the xylenes. The stated quotients at 60°C. are uniformly 2 to 3 times as large as at 30°C. for sec-butylbenzene and more reactive hydrocarbons but 3 to 6 times as large for less reactive hydrocarbons. 

The apparent order of Vp with respect to hydrocarbon depends somewhat on the solvent, as shown in Figure 1. In fert-butylbenzene, which is inert chemically and clearly resembles the xylenes, Vp is first order in hydrocarbon, but deviations occur in o-dichlorobenzene. This principle affects generally the choice of solvents (21). Thus, even in radical oxidation, where solvent effects are much weaker than in ionic reactions, proper choice of solvent is essential if kinetic laws are to be observed over a wide range of reagent concentrations. 

Figure 3. Initial oxidation rate as a function of concentration of cumene in tert-butylbenzene at 60°G. containing 0.06M AIBN and 0.02M ZnP...

Table I. AIBN-Initiated Oxidation of Organic Phosphorus Compounds in ferf-Butylbenzene at 70°C.

Recently, the cobalt(II)-tetrasulfonatophthalocyanine system was reinvestigated for its catalytic activity while intercalated into a Mg5Al2 -layered double hydroxide. The intercalate exhibited catalytic properties in the activation of atmospheric dioxygen for the oxidation of a thiolate to a disulfide (97a) and for the oxidation of 2,6-di-tert-butylbenzene to (nearly exclusively) the 2,6,2, 6 -tetra-tert-butyldiphe-noquinone (97b). In marked contrast to the results reported for the homogeneous catalyst, this intercalated catalyst remained active for... 

Cumene does not undergo oxidation at a measurable rate. 1-Butylbenzene undergoes oxidation mainly in the side chain, with traces of aromatic ring oxidation, producing 1-phenyl-1-butanol, l-phenyI-3-butanol, and the corresponding ketones (Clerici, 1991). 

Cumene or isopropylbenzene, diisopropylbenzene, and secondary butyl-benzene, although produced in smaller quantities than some of the other petrochemical alkylates, are very important petroleum refining products. Cumene is further reacted by oxidation to form cumene hydroperoxide, which is converted to phenol and acetone it is produced by alkylating benzene with propylene catalyzed by either solid or liquid phosphoric acid. Secondary butylbenzene is made by alkylating benzene with normal butylene using the same catalysts. Diisopropylbenzene is made by reacting cumene with propylene over solid phosphoric acid or aluminum chloride catalyst. 

In the above example, t-butylbenzene does not contain a benzylic hydrogen and therefore doesn t undergo oxidation. 

The mechanism of side-chain oxidation is complex and involves utcack on C-H bonds at the poaifion next to th aromatic ring to form intermediate benzylic radicals, fcri-Butylbenzene has no benzylic hydrogens, however, and is therefore inert. 

Ti-MOR promoted the ring hydroxylation of toluene, ethylbenzene and xylenes with negligible oxidation of the ethyl side chain [59]. In the same study, however, and in contrast to earlier ones, a similar result was also reported for TS-1. No oxidation of benzylic methyls was observed. Cumene yielded mainly the decomposition products of cumyl hydroperoxide. The oxidation of t-butylbenzene was negligibly low. The reachvity order, toluene > benzene > ethylbenzene > cumene, reflects the reduced steric constraints in the large pores of mordenite. Accordingly, the rate of hydroxylation ofxylene isomers increased in the order para < ortho < meta, in contrast to the sterically controlled one, ortho < meta para, shown on TS-1. It is worth menhoning that the least hindered p-xylene exhibited the same reactivity on either catalyst. 

One-electron oxidation of aromatic compounds (ArH) leads primarily to corresponding radical cation which exist either in monomeric (ArH +) or dimeric form [(ArH)2 ] the latter usually formulated as r-dimer [70]. However, radical cations are reactive species and can undergo further reaction yielding more persistent radical cations e.g. oxidation of rert-butylbenzene or of toluene or o-xylene yielded radical cation of 4,4 -di-rerf-butyl biphenyl, 4,4 -bitoluene or 3,3, 4,4 -tetramethyl biphenyls, products of further a-coupling, proton loss and further one-electron oxidation [71]. This is a well-known pathway of biaryl dehydrodimerization, explored in anodic and metal-ion oxidation of ArH [72, 73]. Other compounds with high reactivity in (T-coupling are alkoxy and amino substituted ArH [73]. Thus a risk with characterization of radical cations is that hardy survivors and not primary radical... 

Thus, electron transfers from a series of unhindered, partially hindered, and heavily hindered aromatic electron donors (with matched oxidation potentials) to photoactivated quinone acceptors are kinetically examined by laser flash photolysis, and the free-energy correlations of the ET rate constants are scrutinized [31]. The second-order rate constants of electron transfers from hindered donors such as hexaethylbenzene or tri-icrt-butylbenzene strongly depend on the temperature, the solvent polarity and salt effects, and they follow the free-energy correlation predicted by Marcus theory (see Figure 20A). Moreover, no spectroscopic or kinetic evidence for the formation of encounter complexes (exciplexes) with the photo-activated quinones prior to electron transfer is observed. 

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