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 ... 

This is the starting chain and is identical to the IPi species in Equation (13.28), The notation explicitly shows the free-radical nature of the polymerization, and the moiety denoted by I represents a fragment from the chemical initiator e.g. a butyl group when f-butyl peroxide is the initiator. The propagation reaction is... 

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.

Basic solid liquid two-phase conditions with f-butyl peroxide and N-benzylquininium chloride convert cyclohex-2-enone preferentially into the 2(S),3(S)-oxirane (20% ee) which, upon purification and treatment with hydrazine, yields (S)-cyclohex-2-enol [7]. This reaction contrasts with the direct reduction of cyclohex-2-enone to the /J-isomer by lithium aluminium hydride in the presence of quinine [20]. 

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. 

For the formal deoxygenation (decomposition) reaction 5, there is an enthalpy of formation value for every alcohol that matches a hydroperoxide . Using our exemplary groups, R = 1-hexyl, cyclohexyl and ferf-butyl, the liquid enthalpies of reaction are —77.9, —75.0 and —65.6 kJmoR, respectively (there is no liquid phase enthalpy of formation reported for f-butyl peroxide from Reference 4). The secondary hydroperoxides enthalpies of reaction average —77 7 kJmoR. For the three instances where there are also gas phase enthalpies of formation, the enthalpies of reaction are almost identical in the gas and liquid phases. The 1-heptyl (—60.3 kJmoR ) and 1-methylcyclohexyl (—50.6 kJmoR ) enthalpies of reaction are again disparate from the 1-hexyl and tert-butyl. If the enthalpy of reaction 5 for 1-hexyl hydroperoxide is used to calculate an enthalpy of formation of 1-heptyl hydroperoxide, it is —325 kJmoR, almost identical to values derived for it above. The enthalpies of reaction for the liquid and gaseous phases for the tertiary 2-hydroperoxy-2-methylhex-5-en-3-yne are —78.2 and —80.9 kJmoR, respectively. For gaseous cumyl hydroperoxide, the enthalpy of reaction is —84.5 kJmoR. ... 

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) . ... 

ESR measurements on irradiation of 3,3-diethoxycarbonyldiaziridine in f-butyl peroxide showed signals of the diaziridinyl radical (43). The structure of the radical followed from coupling with two N atoms with aN = 14.2 and aN = 11.7 g and one proton with aH = 45.7 g (76TL4205). 

Palladium f-butyl peroxide trifluoroacetate (PPT), CF3C02PdOOC(CH3)3 (1). Mol. wt. 296.52, stable orange crystals. This material can be prepared from Pd(OCOCF3)2 and r-BuOOH or from Pd(OAc)2, t-BuOOH, and CF3COOH (85% yield). 

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... 

Methyl ketones can be catalytically produced when an excess of TBHP is used for regenerating the initial f-butyl peroxide species from the resulting alkoxy complex in Scheme 6- To prevent the formation of a Tr-allylic complex from causing lower selectivities, a large excess of TBHP with respect to the alkene is required (equation 86).260... 

Platinum f-butyl peroxide trifluoroacetate, (CF CC PtlOOCCCh KCHaV COH j 2 (1). Mol. wt. 1168.72, orange powder. This peroxidic complex is prepared by the reaction of f-butyl hydroperoxide with (norbornadiene)Pt(CF3C02)2. 

Thus the primary reaction in di-fe/f-butyl peroxide decomposition is a usual decomposition reaction in the scheme (1.10) the secondary reaction induced by the initial one is described by the scheme (1.11). It is worthy of note that both decomposition reactions are described by the same overall equation, and free radical is the general intermediate particle. 

A source of free radicals is needed to initiate the chain reaction. These free radicals are usually produced by decomposing a peroxide such as di-fe/f-butyl peroxide or benzoyl peroxide, shown below. In the presence of either heat or light, these peroxides decompose to form a pair of free radicals that contain an unpaired electron. 

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