- Oxidation of amines with hyper valent Tert-butylperoxyiodanes: Synthesis of imines and Tert-butylperoxyamino acetalsh
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Reaction of secondary amines with 1-tert-butylperoxy-1,2-benziodoxol-3(1H)-one (2) undergoes dehydrogenation to afford imines in the presence of K2CO3, while oxidation of tertiary amines without base produces tert-butylperoxyamino acetals.
- Ochiai, Masahito,Kajishima, Daisuke,Sueda, Takuya
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- Post-irradiation Decomposition of Sulfanylperoxides and Peroxycyclohexadienethiones formed from Thiyl and Peroxyl Radicals
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Photolysis of (E)-azoisobutane and dialkyl and diaryl disulfides in oxygenated 2-methylbutane at temperatures below 230 K results in a very low photostationary state of peroxyl radical, because of the high efficiency of the mixed termination reaction to form sulfanylperoxide and peroxycyclohexadienethione.Surprisingly, after photolysis is stopped there is an immediate threefold rise in the peroxyl radical concentration.This post-illumination dark reaction is interpreted and accurately modelled using an algorithm, by assuming an irreversible decomposition of the sulfanylperoxide or peroxycyclohexadienethione to alkoxyl and other radicals.Spin traps have been used to confirm the nature of the radicals involved in many of the proposed reactions and to give a measure of radical concentrations under various experimental conditions.Values of the rate parameters for a number of these reactions have been measured and Arrhenius parameters E2 = 34 kJ mol-1, A2 = 106 s-1, E2 = 14 kJ mol-1, A2 = 102.4 s-1 determined for the decomposition of phenyl and tert-butyl sulfanylperoxides, respectively.The low A factor for tert-butyl sulfonylperoxide is probably associated with a tight, four-membered ring transition state with a loss of internal rotations about partially formed sulfur-oxygen double bonds and accompanying solvent orientations about the more dipolar S=O bond.The decomposition of the phenyl analogue occurs by scission of O-O links in para and ortho substituted peroxycyclohexadienethione.
- Mile, Brynmor,Rowlands, Christopher C.,Sillman, Philip D.,Holmes, Andrew J.
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p. 2141 - 2148
(2007/10/02)
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- Dynamics of the reactions of [meso-tetrakis(2,6-dimethyl-3-sulfonatophenyl)porphinato]-manganese(III) hydrate with various alkyl hydroperoxides in aqueous solution. Product studies and comparison of kinetic parameters
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The second-order rate constants (kly) for reactions of [meso-tetrakis(2,6-dimethyl-3-sulfonatophenyl)porphinato]manganese(III) hydrate [(1)MnIII(X)2, X = H2O or HO-] with t-BuOOH and (Ph)(Me)2COOH have been determined in aqueous solution in the pH range 7.3-12.6. The pH dependencies of kly were fitted to a kinetic expression (eq 2) that was similar to that shown previously to describe the pH dependence of the reaction of (1)MnIII(X)2 with (Ph)2(MeOCO)COOH. Comparison of the very similar pH-rate profiles for t-BuOOH, (Ph)(Me)2COOH, and (Ph)2(MeOCO)COOH (ROOH) showed that the log of the second-order rate constants exhibits only a modest dependency on the acidity of the ROH leaving group (-0.32 for the pH 7.3-10.0 range) as would be expected of a homolytic reaction. Product analysis on the reactions with t-BuOOH in the absence of the ABTS trapping agent provided (Me)2CO (60-70%) as the major product with the remainder of the oxidant recovered as t-BuOH (12%), t-BuOOMe, (t-BuO)2, MeOH, and HCHO. The product distributions showed no significant dependence on the pH of the reaction solutions. In the presence of ABTS (Me)2CO is formed in 5% yield, and the main product is t-BuOH (89%). These findings are consistent with a mechanism involving the homolytic (but not heterolytic) cleavage of the O-O bond of manganese(III)-coordinated alkyl hydroperoxide. Addition of imidazole to the reaction of (1)MnIII(X)2 with t-BuOOH resulted in a ~4-10-fold enhancement in the rate of reaction. The pH dependence of log klm for the reaction in the presence of imidazole, from pH 5.3 to 12.6, was found to be in accord with that determined previously for (Ph)2- (MeOCO)COOH. The product distribution for the reactions in the presence of imidazole showed significant dependence on the pH of the reaction mixtures. At pH 7.8 and 10.0 the product profiles were only consistent with a homolytic mechanism for the O-O bond cleavage where the major product was (Me)2CO (63-67%), with the remainder being t-BuOH (19%), t-BuOOMe (13-16%), (t-BuO)2, MeOH, and HCHO. At pH 12.6, the yield of t-BuOH (63%) increased dramatically with concomitant decreases in the yields of (Me)2CO (34%), t-BuOOMe (4%), (t-BuO)2, MeOH, and HCHO. The latter product distribution finds explanation in a change in mechanism of the O-O bond cleavage from homolysis to heterolysis as a result of the proton dissociation of the manganese(III)-coordinated ImH (i.e., (1)MnIII(OOR)(ImH) → [(1)MnIII(OOR)(Im)]-). The acidity dependences of the 1e- oxidation and reduction potentials of (1)MnIII(X)(ImH) have been used to determine the acid ionization constants for the mono-imidazole-ligated (1)MnII(H2O)(ImH), (1)MnIII(H2O)(ImH), and (1)MnIII(H2O)(ImH) species. The change in 1e- oxidation potentials with pH has also been compared to the change in rate constants with pH for reactions occurring in the presence and absence of imidazole.
- Arasasingham, Ramesh D.,Jeon, Seungwon,Bruice, Thomas C.
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p. 2536 - 2544
(2007/10/02)
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- Reactions of Oxygenated Radicals in the Gas Phase. Part 14. Reactions of t-Butylperoxyl Radicals
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The photo-oxidation of trans-2,2'-azoisobutane has been studied between 313 and 393 K.The principal products are acetone, t-butyl alcohol, t-butyl hydroperoxide, and formaldehyde.The yields of hydroperoxide and formaldehyde come to a limiting value during photolysis.Detailed analyses of products were carried out at different temperatures and total pressures.Further experiments were performed in which t-butyl hydroperoxide was added.The reaction was simulated over this wide range of conditions.The importance of reactions between the various alkylperoxyl radicals is emphasised.
- Osborne, David A.,Waddington, David J.
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p. 1861 - 1868
(2007/10/02)
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