Terf-Butyl hydrogen peroxide

Jackson has reported a similar process using tartrate ligands, magnesium as the metal and terf-butyl hydrogen peroxide as the oxidant [55]. Enantiomeric... 

The three saturated long-chain tert-butyl peresters are members of a homologons series, and as such, the weighted least-squares regression analysis of the enthalpies of formation V5. number of carbons yields a methylene increment of —26.7 kJmol , a typical valne for liquids. The methylene increment for the terf-butyl esters of the Cg, Cjo, Cn and C14 acids is —28.0 kJmol. The closeness of these two values ensures that the enthalpies of formal reaction 16 will be nearly constant. For the three pairs from Table 3, the value is —70.3 8.1 kJmol. The standard deviation from the mean is quite large because the arithmetic difference for the C12 ester and perester, —79.5 kJmol, is quite a bit more negative than the differences for the Cio and C14 pairs, —64.4 and —66.9 kJmol, respectively. Unfortunately, the acids and esters are in different phases and so we are reluctant to attempt any comparison between them, such as a formal hydrolysis reaction or disproportionation with hydrogen peroxide. 

Since 19951, to the best of our knowledge, there have appeared few papers detailing structural investigations of silyl radicals. Of those few, Matsumoto and coworkers investigated the isomerization of silyl radicals derived from 9,10-di-terf-butyl-9,10-dihydro-9, 10-disilaanthracenes (2)6. Irradiation of a di-terf-butyl peroxide (DTBP)/pentane solution of either cis-2 or trans-2 affords the same 81% cist 19% trans mixture of 2. In the absence of DTBP and irradiation, solution NMR studies indicate that each isomer of 2 is unchanged in the —85 to 20 °C temperature range. The authors propose that the radicals 3 derived from 2 isomerize to each other via inversion of the radical centre (equation 1) followed by hydrogen abstraction from the parent compound 2 (an identity reaction). 

A similar increase in reactivities in the methyl-methylene-methine series is found in the free-radical oxidations of lower alkanes with oxygen in the presence of hydrogen bromide as an initiator of the reaction. Ethane gives a 64% yield of acetic acid at 220 °C, propane gives a 72% yield of acetone at 189 °C, and isobutane gives a 69.5% yield of terf-butyl hydroperoxide, a 10% yield of fm-butyl alcohol, and a 6% yield of di-rm-butyl peroxide at 163 °C [54],... 

Alkyl radicals can be obtained by abstraction of a hydrogen atom from an alkyl group by another radical. This method was utilized for the generation of benzyl radicals from toluene with tert-butoxy radical obtained on heating di-terf-butyl peroxide.38 Benzoyl92 and carboxymethyl88 radicals have also been obtained by this method. The reaction gives rise to a complex mixture of products and therefore is of rather limited use. 

Many types of peroxides (R-O-O-R ) are also utilized, including diacyl peroxides, peroxydicarbonates, peroxyesters, dialkyl peroxides, and inorganic peroxides such as persulfate, the latter being used mainly in water-based systems. The rate of peroxide decomposition as well as the subsequent reaction pathway is greatly affected by the nature of the peroxide chemical structure, as illustrated for fert-butyl peroxyesters in Scheme 4.2. Pathway (a), the formation of an acyloxy and an alkoxy radical via single bond scission, is favored for structures in which the carbon atom in the a-position to the carbonyl group is primary (for example, terf-butyl peroxyace-tate, R = CHg). Pathway (b), concerted two-bond scission, occurs for secondary and tertiary peroxyesters (for example, terf-butyl peroxypivalate, R = C(CH3)3) [1, 2]. The tert-butoxy radical formed in both pathways may decompose to acetone and a methyl radical, or abstract a hydrogen atom to form tert-butanol. 

In the putative catalytic cycle, the catalyst deprotonates TBHP to form the active catalytic species, the alkyl-ammonium / terf-butyl peroxy ion pair. The hydroxyl group acid-activates the enone by forming a hydrogen bond with the carbonyl group while the peroxide adds in Michael-fashion. The intermediate enolate attacks the 0-0 bond intramolecularly and forms the epoxide and the tcrt-butoxide anion. Finally, the ferf-butoxide acts as base to regenerate the catalyst. 

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