Di-f-butyl peroxide

In the case of allyl peroxides (12 X= CH2, A=CH2, BO),1 1 1 intramolecular homolytic substitution on the 0-0 bond gives an epoxy end group as shown in Scheme 6.18 (1,3-Sn/ mechanism). The peroxides 52-59 are thermally stable under the conditions used to determine their chain transfer activity (Table 6.10). The transfer constants are more than two orders of magnitude higher than those for dialkyi peroxides such as di-f-butyl peroxide (Q=0.00023-0.0013) or di-isopropyl peroxide (C =0.0003) which are believed to give chain transfer by direct attack on the 0-0 bond.49 This is circumstantial evidence in favor of the addition-fragmentation mechanism. 

Di-f-butyl peroxide is a commonly used free-radical initiator that decomposes according to first-order kinetics. Use the following data to estimate AVact for the decomposition in toluene at 120°C ... 

Photolysis of dicyclopentadienyltin results in formation of the Cp- radical (again detected by ESR), along with the precipitation of some unidentified yellow solid54. In contrast, photolysis of dicyclopentadienyllead produces no Cp-, unless di-f-butyl peroxide or biacetyl are added to the reaction mixture. The trimethylstannylcyclopentadienyl radical was produced by photolysis of bis(trimethylstannyl)cyclopentadiene (reaction 35), and was detected using ESR spectroscopy57. 

Some examples, such as thermal polymerization of styrene and decomposition of di-f-butyl peroxide, are given in [194], both treated as first-order reactions. The activation energy found for the decomposition of di-f-butyl peroxide agrees well with the literature value. From the pressure data, it appears that the initial pressure rise is caused by the evaporation of toluene, present as a solvent. At higher temperatures, the gases generated by decomposition are the main contributors to the pressure rise. 

The kinetic resolution of racemic trans ester 76a using catalytic amounts of chiral amine-borane 78 and di-f-butyl peroxide as initiator under pho-tolytic conditions at - 74 °C provided the enantioenriched (R,R) product in 74% ee after 52% consumption of the racemate [64-67]. For the ester 76b, (R,R) product in 97% ee was isolated after 75% consumption at -90°C (Scheme 20). 

Scheme 4. Initiation of Vinylidene Chloride Polymerization Using Di-f- butyl Peroxide (TBPO) as Initiator.

A number of reports on the thermal decomposition of peroxides have been published. The thermal decompositions of f-butyl peroxyacetate and f-butyl peroxypivalate, of HCOH and a kinetic study of the acid-induced decomposition of di-f-butyl peroxide in n-heptane at high temperatures and pressures have been reported. Thermolysis of substituted f-butyl (2-phenylprop-2-yl) peroxides gave acetophenone as the major product, formed via fragmentation of intermediate alkoxy radicals RCH2C(Ph)(Me)0. A study of the thermolysis mechanism of di-f-butyl and di-f-amyl peroxide by ESR and spin-trapping techniques has been reported. The di-f-amyloxy radical has been trapped for the first time. jS-Scission reaction is much faster in di-f-amyloxyl radicals than in r-butoxyl radicals. The radicals derived from di-f-butyl peroxide are more reactive towards hydrogen abstraction from toluene than those derived from di-f-amyl peroxide. 

The HPLC method with CLD described in Section V.B.2.C for determination of hydroperoxides using luminol (124) with hemin (75a) catalysis is ineffective with dialkyl peroxides, such as di-f-butyl peroxide, cumyl propyl peroxide and cumyl 3-phenylpropyl peroxide. However, for a certain set of experimental conditions, cumyl aUyl peroxide can be determined, but the sensitivity is much lower than for hydroperoxides . ... 

Oxidation of 1,4-thioxane by BTSP and f-butyl(trimethylsilyl) peroxide in CHCI3 at 25 °C is compared to those of the same substrate by the more common oxidants, f-butyl hydroperoxide and di-f-butyl peroxide, in the same solvent. The two silyl peroxides give similar oxidations rates, which are over 50 times higher than that measured for f-BuOOH, while f-Bu202 is almost unreactive under the conditions adopted. Oxidation... 

The compounds 43, 45, 48b and 48c gave the corresponding disUoxanes in quantitative yields, and BTSP is converted into hexamethyldisUoxane, 44, formed from difluorote-tramethyldisiloxane. The reaction of 44 with BTSP was not inhibited by 2,4,6-tri(t-butyl)phenol. Compound 48a did not react with di-f-butyl peroxide, which is the carbon analog of BSTP, suggesting an important role of vacant rf-orbitals of the silicon atom. The Si—Si oxidation of compound 49 with BSTP proceeds quantitatively and in a stereospecific fashion (equation 72) . ... 

Fig. 21. Inverse recombination probability of f-butyl radicals formed from O, di-f-butyl peroxide (DBP) by photo-dissociation , di-f-butyl hyponitrite (DBH) by thermal dissociation and A, di-f-butyl peroxyoxalate (DBPO) by thermal dissociation plotted against the inverse viscosity of the solvent. The temperature was 45°C. After Kiefer and Traylor [288 ].

Deoxygenation of esters. Esters can be reduced to hydrocarbons by (QH5)3SiH in the presence of a radical generator, di-f-butyl peroxide, at 140°. Highest yields are obtained with acetates yields based on the alcohol decrease in the order secondary > primary > tertiary. Other silanes are much less effective than triphenylsilane, which is required in excess for high yields. Radical initiators such as AIBN or benzoyl peroxide are not useful.1... 

Sodium ra-chloroperbenzoate, 73 Trifluoroperacetic acid, 258 Triphenylsilane-Di-f-butyl peroxide, 334 Phase-transfer catalysts Adogen 464, 258, 281... 

Some polysiloxanes are curable with lead monoxide, with a consequent reduction in both curing time and temperature. High-frequency electrical energy vulcanizes in one case at least. Zirconium naphthenate imparts improved resistance to high temperatures. Barium salts are said to prevent blooming. Sulfur dichloride is also used. Some resins are solidified by pressure vulcanization, using di-f-butyl peroxide. Improvements are to be found in lower condensation temperatures and shorter times of treatment... 

When Blake and Kutschke23 studied the reaction of methyl radicals with formaldehyde they used di-f-butyl peroxide (DTBP) as a source of... 

The photochemical dissociation of di-(-butyl peroxide appears to proceed in a very similar way to the thermal decomposition. Dorfman and Salsburg47 photolyzed di-(-butyl peroxide using 2537 and 2650 A. radiation between 25 and 75°C. They found that the main products were ethane and acetone in relative yields of 1 2. With low intensity radiation, some methane was obtained and, even though acetone was removed to prevent its reactions becoming appreciable, (-butanol was produced. The evidence is therefore very strong that di-f-butyl peroxide decomposes by the usual breaking of the peroxide 0—0 bond and the (-butyl radicals then rapidly decompose to give acetone and methyl radicals, i.e.,... 

Fig. 5. Photolysis of 10.5 mm. di-f-butyl peroxide in the presence of 3.5 mm. oxygen at 50.2°C. (Hoare and Wellington87).

When 34 mm. benzene was added, the formaldehyde obtained decreased a little only in the early stages of the oxidation of di-f-butyl peroxide, which could be attributed to reaction (20) becoming more important than reaction (18). Similarly, at low oxygen pressures, more carbon monoxide was formed. This could be explained by the greater importance of reaction (71) followed by reactions (18) and (75). These explanations tended to show that a fair number of methyl radicals were produced by decomposition of di-f-butyl peroxide. 

Methylation is taken as illustrative of alkylation for comparative purposes in Table 25 however, a wide range of other alkylations have been studied (76M120503). Photolysis of di-f-butyl peroxide in a mixture of cyclohexane and pyridine gives cyclohexylation (equation 170) (71CR(C)(272)854>. The relative rates for homolytic substitution of pyridines by cyclic alkyl radicals have been obtained (74JCS(P2)1699>. A striking contrast can be seen (Table 26)... 

Chlorohydroxylation of alkenes.1 Anhydrous f-butyl hydroperoxide or di-f-butyl peroxide (1, 211-212) in the presence of TiCl4 effects chlorohydroxylation of alkenes. The reaction shows moderate to high regioselectivity as well as fair to good diastereo-selectivity when the substrate is substituted in the allylic or homoallylic position. Examples ... 

Not surprisingly, adenine and guanine have been a major focus of many studies in this field and in alcohol solutions with irradiation at wavelengths >290 nm, 8-hydroxyalkyl derivatives are produced. The yields are improved by use of sensitizers such as acetone and di-f-butyl peroxide (73JOC3420). With substituted purines, attack may also occur at the substituent group as with caffeine which in 2-propanol produced (174). 

In the case of the successful Ni(II) cyclization, the initial report (1964) indicated that the reaction could be carried out by irradiating with a 200 W tungsten lamp. It was later determined (in 1966) that, in contrast to the case of the metal-free dideoxybiladienes, light did not serve to activate this particular metal-dependent cyclization. Conversely, the presence of a base was found to be essential." As part of this 1966 study, it was also found that cyclization of the metal(II)dideoxybiladienes-ac in the presence of di-f-butyl peroxide afforded only small yields of a mixture of macrocycles. The above results led to the suggestion that the cyclization of metal(II)dideoxybiladienes-ac does not proceed via a free-radical mechanism. It was thus proposed that the initial reaction involved abstraction of a proton from the central (C(10)) methylene group of the dideoxybiladiene-ac. 

Reactions of peroxides with triphenylphosphine usually result in monodeoxygenation. Dialkyl peroxides react relatively slowly with triphenylphosphine and give ethers as the major products for example, di-f-butyl peroxide gave di-f-butyl ether (81%) after being heated with triphenylphosphine at 110-120 C for 30 h. The mechanism suggested for these reactions is an ionic one, triphenylphosphine acting as a nucleophile. The reaction illustrated in Scheme 29 can then be rationalized by the loss of triphenylphosphine oxide and intramolecular attack on the double bond. The reaction has found several useful applications in synthesis an example is a preparation of naphthalene 1,2-oxide (Scheme 32). 

O, direct photolysis at 3130 A O, CH3 from azomethane 0, CH3 from di-f-butyl peroxide. 

Di-f-butyl nitroxide, 129,461 Di-f-butyl peroxide, 123 Di-f-butylquinones, 121 Di-n-butyl sulfide, 6 Di-n-butyl sulfoxide, 6... 

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