T Butyl hydroperoxide TBHP

SHARPLESS Asymmetne Epoxidation EnanlioselectK/e epoxidation of altyl alcohois by means of Irtanlum a5(oxide, (+) or () diethyl tartarate (OET) and t butyl hydroperoxide (TBHP)... 

The method is applicable to a wide range of substrates. Table 4.4 gives various a, (3-enones that can be epoxidized with the La-(R)-BINOL-Ph3PO/ROOH system. The substituents (R1 and R2) can be either aryl or alkyl. Cumene hydroperoxide can be a superior oxidant for the substrates with R2 = aryl group whereas t-butyl hydroperoxide (TBHP) gives a better result for the substrates with R1 = R2 = alkyl group. 

Butter, peroxide value, 658, 660, 665 t-Butyl alcohol, tetroxide formation, 740 t-Butyl cumyl peroxide air pollutant, 622 determination, 707 hydroperoxide determination, 685 t-Butyl hydroperoxide (TBHP)... 

Gold-catalyzed oxidation of styrene was firstly reported by Choudhary and coworkers for Au NPs supported on metal oxides in the presence of an excess amount of radical initiator, t-butyl hydroperoxide (TBHP), to afford styrene oxide, while benzaldehyde and benzoic acid were formed in the presence of supports without Au NPs [199]. Subsequently, Hutchings and coworkers demonstrated the selective oxidation of cyclohexene over Au/C with a catalytic amount of TBHP to yield cyclohexene oxide with a selectivity of 50% and cyclohexenone (26%) as a by-product [2]. Product selectivity was significantly changed by solvents. Cyclohexene oxide was obtained as a major product with a selectivity of 50% in 1,2,3,5-tetramethylbenzene while cyclohexenone and cyclohexenol were formed with selectivities of 35 and 25%, respectively, in toluene. A promoting effect of Bi addition to Au was also reported for the epoxidation of cyclooctene under solvent-free conditions. 

Aqueous 70 per cent t-butyl hydroperoxide (TBHP) is obtained from Aldrich Chemical Co. 

The process originally developed by Halcon/ARCO, with a current market share of ca. 18%, is based on the use of t-butyl hydroperoxide (TBHP) as the oxidant (Figure 13, = CH3, Equation 17,18). Isobutane is oxidized... 

Since water is detrimental to catalytic performance, and its presence is unavoidable with hydrogen peroxide as the oxidant, an alternative consists of the use of t-butyl hydroperoxide (TBHP), compatible with the pores of Ti-Beta zeolites and with external pockets of Ti-MWW. In the case of the former catalysts, rates are lower than with hydrogen peroxide while with Ti-MWW they are comparable [79, 83]. It should be considered, however, that in this use both large-pore Ti-zeolites and mesoporous Ti-silicates are in competition with the cheaper and easier to prepare Ti/Si02. 

Ti, V and Sn-modified mesoporous silicates were reported to be active in a number of liquid phase oxidation reactions. Ti-containing samples were used for the selective oxidation of large organic molecules in the presence of te/t-butyl hydroperoxide (TBHP) or dilute H2O2 [71,136,137,139-141,147,186,237]. Typical data shown in Table 5 indicate that both Ti-MCM-41 and Ti-HMS are efficient cat ysts for the epoxidation of bulky olefins such as a-terpineol and norbomene in the presence of TBHP or H2O2. Comparison with H-B indicates that the accessibility of active sites plays a critical role in the liquid phase oxidation of organic molecules. Mesoporous titanosilicates also exhibited remarkable activity in the hydroxylation of 2,6-di-rerr-butyl phenol (2,6 DTBP) [142,147] and the oxidation of cyclododecanol [147], naphthol [147] aniline [237] and chloroaniline [186]. However, they were disappointingly poor catalysts for the liquid phase oxidation of n-hexane and aliphatic primary amines, as well as the ammoximation of cyclohexanone [147,238]. 

These complexes are easily prraared from the reaction of t-butyl hydroperoxide (TBHP) or cumyl hydroperoxide with the V-oxohydroxo complex (equation 10). The X-ray structure of VO(dipic)(OOBu )(H20) (22) revealed a pentagonal bipyramidal environment with an 0—0 triangularly bonded t-butyl peroxide group. This structure is comparable with that of the V -peroxo complex [V0(02)(dipic)(H20)]NH4 and the V -0,7V-hydroxylamino complex VO(dipic)-(0NH2)(H20).2 2... 

Isobutane oxidation is performed in the liquid phase at 130-160 °C and elevated pressures. Since this exceeds the critical temperature of isobutane (134 °C), products (TBA, t-butyl hydroperoxide (TBHP)) must be present to maintain a liquid phase. The epoxidation step is performed at 100-130 °C using 10-300 ppm of Mo. Since propene is a rather unreactive olefin, a high propene/TBHP molar ratio is used to suppress nonproductive decomposition of TBHP. The high propene concentration leads to very high operating pressures and high recycle costs. The PO and TBA products are purified by a combination of direct and extractive distillation. TBHP conversion and PO selectivity are in excess of 90 %. 

A case in point is "dilution study". When using hazardous reactants such as benzoyl peroxide (BPO) or t-butyl hydroperoxide (TBHP) which are both labelled as hazardous by CHETAH, one can perform hazard evaluations at different concentrations in a stable (non-hazardous) solvent. This allows for selection of a safe concentration for initial scale-up studies in process development. The effect of dilution with xylene on the maximum enthalpy of decomposition of the above peroxides is shown below ... 

The oxidation reactions were performed in a closed, mechanically stirred 100 ml glass batch reactor under Ar. For the epoxidation of a-isophorone, 0.2 g catalyst, 9 ml solvent, 7.2 mmol cumene (internal standard) and 77 mmol olefin were introduced into the reactor. The slurry was heated to the reaction temperature and the reaction stauted by adding 13.4 mmol t-butyl hydroperoxide (TBHP, ca. 3 M in isooctane) from a dropping funnel to the vigorously stirred slurry (n = 1000 min ). For the epoxidation of P-isophorone, 20 ml ethylbenzene solvent, 61 mmol P-isophorone, 7.2 mmol cumene and 5.6 mmol TBHP or ciunene hydroperoxide (CHP) were introduced into the reactor in this order. The solution was heated to 80 °C and... 

Several solvents have been tested in the epoxidation of a- isophorone with t-butyl hydroperoxide (TBHP). The best performance of the aerogel was observed in low polarity solvents such as ethylbenzene or cumene (Table 1). In these solvents 99 % selectivity related to the olefin converted was obtained at 50 % peroxide conversion, independent of the temperature. Rasing temperature resulted in increasing initial rate and decreasing selectivity related to the peroxide. The low peroxide efficiency is explained by the homol5d ic peroxide decomposition. Protic polar solvents were detrimental to the reaction due to their strong coordination to the active sites. There was no epoxide formation in water. 

The polymerization of the adducts was carried out by adding 0.2ml of either t-butyl peracetate (tBPA), t-butyl perbenzoate (tBPB) or t-butyl hydroperoxide (tBHP-70 containing 70% tBHP and about 30% di-t-butyl peroxide or tBHP-90 containing 90% tBHP and about 10% t-butyl alcohol), by syringe in four equal portions over a 20 min period to 2g of the adduct in a rubber-capped tube immersed in a constant temperature bath. The mixture was then maintained at temperature for an additional 40 min. Reactions at 120°C were conducted in 3ml chlorobenzene. The reaction product was dissolved in acetone and precipitated with methanol twice. 

The first indication of selective substitution reactions came from experiments with 1 and 2 as catalysts for alkene epoxidation. NMR experiments have shown that both compounds catalyze the epoxidation of cyclohexene with t-butyl hydroperoxide (TBHP). The catalytic activity is comparable to that of the model compound Hex7Si70i2Ti(0 Pr). " The measured turn over numbers indicate that all four Ti centers are involved in the catalytic process. The catalysts could be recovered quantitatively, a proof of core-functionalization and for the core stability during many catalytic cycles. A more detailed catalytic study has recently been performed with the cubic titanasiloxane [(2,6- Pr2C6H3) (Me3Si)NSi]40i2[Ti0 Bu]4 (12). This compound was prepared by the reaction of 9 with t-butanol and catalyzes the epoxidation of cyclohexene with TBHP. The titanium butylperoxo intermediate could be isolated after a stoichiometric reaction with TBHP. This intermediate then reacted with cyclohexene to produce cyclohexene oxide. A schematic representation of the catalytic process is given in Figure 28.4. 

The example furthermore shows that diffusion from the bulk fluid phase toward the volume near the IRE, which is probed by the evanescent field, has to be accounted for because it may be the limiting step when fast processes are investigated. The importance of diffusion is more pronounced when a catalyst layer is present on the IRE, because of the diffusion in the porous film is much slower than that in the stagnant liquid film. Indeed, the ATR method, because of the measurement geometry, is ideally suited to characterization of diffusion within films (50,66-68). Figure 16 shows the time dependence of absorption signals associated with cyclohexene (top) and t-butyl hydroperoxide (TBHP, bottom). Solutions (with concentrations of 3mmol/L) of the two molecules in cyclohexane and neat cyclohexane were alternately admitted once to... 

While the detailed mechanism of H2O2 decomposition by 1 is not known yet, we are interested if related organic hydroperoxides can be decomposed. The surprising results, shown in Figure 4, is that 1, which contains the Mn(II)Mn(III)3 core, does not decompose significantly either cumene hydroperoxide (CHP) or t-butyl hydroperoxide (TBHP). In contrast, Mn(II) and Mn(III) acetates decompose CHP. The lack of decomposition of ROOH by 1 combined with its catalytic activity reconmiend Mn4 complexes as candidates for oxidation catalysts. 

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