Hydroperoxide Tetralin

Submitted by H. B. Knight and Daniel Swern.1 Checked by John C. Sheehan and Curt W. Beck. 

In a 1-1. round-bottomed three-necked flask, equipped with a thermometer, a reflux condenser, and two fritted-glass gas dis- 

Rubber connections must be avoided because rubber is rapidly attacked by tetralin. Convenient gas dispersion tubes are Pyrex No. 39533. 

Active oxygen content is determined iodometrically 3 In an iodine flask, an accurately weighed sample (0.1-0.3 g.) is dissolved in 20 ml. of an acetic acid-chloroform solution (3 2 by volume), and 2 ml. of saturated aqueous potassium iodide solution is added. The flask is immediately flushed with nitrogen, stoppered, and allowed to stand at room temperature for 15 minutes. Fifty milliliters of water is then added with good mixing, and the liberated iodine is titrated with 0.1 A sodium thiosulfate, employing starch as indicator. A blank titration, which usually does not exceed 0.2 ml., is also run. One milliliter of 0.1 N sodium thiosulfate is equivalent to 0.00821 g. of tetralin hydroperoxide. 

The distillation should be conducted behind a safety shield. 

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Pt(II)(8-quinolinolate), Tb(III)(TTFA)3(o-phen) with TTFA = thenoyltrifluoroacetonate and o-phen = 1.10— phenanthroline, Tb(III)(TTFA) , and Eu(III)(TFFA)3 (o-phen). An eel of Re(o-phen)(CO)3C1 occured during the electrolysis of tetralin hydroperoxide in the presence of the rhenium compound. The mechanism of these electrochemical reactions is discussed. 

In 1981 we found that Re(o-phen)(COj Cl shows an intense chemiluminescence during the catalytic decomposition of tetralin hydroperoxide (THPO) in boiling tetraline (1 2). 

The three solid phase tetralin and decalin hydroperoxides have enthalpies of reaction that are surprisingly comparable, —93.9 6.4 kJmoR, despite the sometimes large error bars associated with either the peroxide or corresponding alcohol and their differences in structure. Notably, the gas phase reaction enthalpy for the cumyl hydroperoxide is nearly identical to the solid phase reaction enthalpy for the 1-methyl-1-tetralin hydroperoxide, —87.0kJmoR, for these structurally similar compounds and supports the hypothesis that the gas and condensed phase formal reaction enthalpies are nearly the same for all compounds. Flowever, for 2,5-dimethylhexane-2,5-dihydroperoxide, the enthalpies of reaction 5 per hydroperoxy group for the solid and gaseous phase are not close —57 and —76 kJmoR, respectively. Compare them with the enthalpies of reaction for ferf-butyl hydroperoxide of —66 (Iq) and —67 or —78 (g) kJmoR. For the unsaturated counterpart, 2,5-dimethylhex-3-yne-2,5-dihydroperoxide, the solid and gas phase enthalpies of reaction per hydroperoxy group are —64.2 kJmoR and —74.6 kJmoR, respectively. 

Tetralin hydroperoxide (1,2,3,4-tetrahydro-l-naphthyl hydroperoxide) and 9,10-dihydroanthracyl-9-hydroperoxide were prepared by oxidizing the two hydrocarbons and purified by recrystallization. Commercial cumene hydroperoxide was purified by successive conversions to its sodium salt until it no longer increased the rate of oxidation of cumene at 56°C. All three hydroperoxides were 100% pure by iodometric titration. They all initiated oxidations both thermally (possibly by the bi-molecular reaction, R OOH + RH — R O + H20 + R (33)) and photochemically. The experimental conditions were chosen so that the rate of the thermally initiated reaction was less than 10% of the rate of the photoreaction. The rates of chain initiation were measured with the inhibitors 2,6-di-ter -butyl-4-methylphenol and 2,6-di-fer -butyl-4-meth-oxyphenol. None of the hydroperoxides introduced any kinetically first-order chain termination process into the over-all reaction. 

Co-oxidation of Cumene and Tetralin. The present method for determining cross-propagation constants is based on Thomas and Tolman s (34) observation that the oxidation of cumene is strongly inhibited by adding low concentrations of Tetralin hydroperoxide. These workers concluded that TOO radicals formed in the transfer reaction ... 

The rate of oxidation of 6.7M cumene in chlorobenzene at 30°C. was found to be decreased to a constant value by adding 0.1M Tetralin hydroperoxide. At this point, all the COO radicals are being converted into TOO radicals without undergoing any other reactions. Hence, the TOO radicals are propagating and terminating the chain. The propagation constant is the cross constant kp (Reaction 5) and the termination constant is kt. The rate is given by... 

Tetralin hydroperoxide has little or no effect on the thermally or photochemically initiated oxidation of Tetralin, nor are the absolute rate constants for the oxidation of Tetralin (1.7M in chlorobenzene) affected by adding 0.1M [TOOH] (Table I). [Hydrogen-bonded peroxy radicals are either unimportant in this system or have the same reactivity as the peroxy radicals formed in the absence of hydroperoxide. A similar conclusion applies to propagation in cumene and cumene-COOH mixtures (see Table I).]... 

Hydrogen Atom Transfer from Hydroperoxides to Peroxy Radicals. The reaction of cumylperoxy radicals with Tetralin hydroperoxide (Reaction 10) can be studied at hydroperoxide concentrations below those required to reduce the oxidation rate to its limiting value. The rate of oxidation of cumene alone can be represented by ... 

Table IV. Effect of Tetralin Hydroperoxide on Autoxidation of Cumene at 30°C.

Figure 1. Effect of Tetralin hydroperoxide on autoxidation of cumene at 30°C.

Table VI. Effect of tert-Butyl Alcohol on Hydrogen Atom Transfer from Tetralin Hydroperoxide to Cumyl Peroxy Radicals at 30°C.

Table VII. Rate Constants (in Mole"1 Sec."1) for Hydrocarbon Oxidation in Absence and Presence of 0.1 to 0.4M Tetralin Hydroperoxide at 30°C.

In the presence of 0.1 to 0.4M Tetralin hydroperoxide the measured termination constants for toluene, ethylbenzene, and cumene are in good agreement with the value 3.8 X 10° Mole"1 sec."1 obtained with pure Tetralin. Since the variations in the measured values are within the limits of experimental error, the cross-propagation constants, kp, were obtained using this termination constant and the measured values of 1 /(2It )1/2. 

Materials. Chemically pure solvents and reagent grade ceric ammonium nitrate were used as received. Cumene hydroperoxide was purified via the sodium salt. Lucidol tert-butyl hydroperoxide was purified by low temperature crystallization. Tetralin hydroperoxide, cyclohexenyl hydroperoxide, and 2-phenylbutyl-2-hydroperoxide were prepared by hydrocarbon oxidation and purified by the usual means. 1,1-Diphenyl-ethyl hydroperoxide and triphenylmethyl hydroperoxide were prepared from the alcohols by the acid-catalyzed reaction with hydrogen peroxide (10). 

Several other types of antioxidants can inhibit oxidation by donating a hydrogen atom to a peroxy radical. Howard (15) has described the interesting case of inhibition by a second hydrocarbon or its hydroperoxide. In the particular case he discussed, the inhibition of the oxidation of cumene by Tetralin (TH) or Tetralin hydroperoxide (TOOH) occurs because the tetralylperoxy radical (T02 ) reacts with a cumylperoxy radical (CO2 ) much more rapidly than two cumylperoxy radicals react with one another. The inhibition sequence can be represented by the following reactions. 

Tetralin Hydroperoxide Detonated by superheating H. Hock W. Susemiehl, Ber 66, 22 (1944)... 

Pure tetralin hydroperoxide has an active oxygen content of 9.74%. 

Tetralin hydroperoxide is a convenient model compound for many studies in peroxide chemistry. It remains colorless and does not decrease in peroxide content for months if stored in the dark at or below 0°. Storage under warm summer conditions for several months results in decomposition to a dark, viscous liquid. 

Tetralin Hydroperoxide. See in Vol 8, P207-L under 1,2,3,4-Tetrahydro-l-Naphthyl Hydroperoxide and the following Addril Refs J.S. McDonald J.S. Owens, Investigation of Tetralin Explosion , NAA-SR-4803, Atomics Intrnl, Canoga Park, Contract AT (1 l-l)-GEN-8 (1960) [An expln in a Na-tetralin heat exchanger is reported as being caused by the unforeseen formation of a-tetralin hydroperoxide. The decompn ° hydroperoxide to Oi-tetralone... 

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