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78-93-3Relevant articles and documents
Fluorescence excitation spectrum of the 2-butoxyl radical and kinetics of its reactions with NO and NO2
Lotz,Zellner
, p. 2607 - 2613 (2001)
The (A ← X) fluorescence excitation spectrum of the 2-C4H9O(X) (2-butoxyl) radical in the wavelength range 345-390 nm was obtained using a combined laser photolysis/laser-induced fluorescence (LIF) technique following the generation of the radicals by excimer laser photolysis of 2-butylnitrite at λ = 351 nm. The fluorescence excitation spectrum shows 5 vibronic bands, where the dominant progression corresponds to the CO-stretching vibration in the first electronically excited state with v′CO = (560 ± 10) cm-1. The transition origin was assigned at v00 = (26768 ± 10) cm-1 (λ00 = (373.58 ± 0.15) nm). The kinetics of the reactions of the 2-butoxyl radical with NO and NO2 at temperatures between T = 223-305 K and pressures between p = 6.5-104 mbar have been determined. The rate coefficients for both reactions were found to be independent of total pressure with kNO = (3.9 ± 0.3) × 10-11 cm3 s-1 and kNO2 = (3.6 ± 0.3) times; 10-11 cm3 s-1 at T = 295 K. The Arrhenius expressions have been determined to be kNO = (9.1 ± 2.7) × 10-12 exp((3.4 ± 0.6) kJ mol-1/RT) cm3 s-1 and kNO2 = (8.6 ± 3.3) × 10-12 exp((3.3 ± 0.8) kJ mol-1/RT) cm3 s-1. In addition, the radiative lifetime of the 2-C4H9O(A) radical after excitation at λ = 365.938 nm in the (0,1) band has been determined to be τrad(2-C4H9O(A)) = (440 ± 80) ns. Quenching rate constants of the 2-C4H9O(A) radical were measured to be kq = (4.7 ± 0.3) × 10-10 cm3 s-1 and kq = (5.0 ± 0.4) × 10-12 cm3 s-1 for 2-butylnitrite and nitrogen, respectively.
Homogeneous Hydrogenation of α,β-Unsaturated Ketones and Aldehydes Catalyzed by Co2(CO)8-Di(tertiary phosphine) Complexes
Murata, Kazuhisa,Matsuda, Akio
, p. 1899 - 1900 (1981)
The cobalt complexes modified by some di(tertiary phosphine)s as ligands were found to be much more active catalysts than Co2(CO)8 for the hydrogenation of α,β-unsaturated ketones and aldehydes under hydroformylation conditions.
Isoxazoles. 8. Preformulation studies of an isoxazolylnaphthoquinone derivative
Longhi,De Bertorello,Granero
, p. 336 - 338 (1994)
The degradation kinetics of 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4- naphthoquinone 4-imine (1) in a 25% solution of ethyl alcohol in water has been studied. The rate constants were observed to follow pseudo-first-order kinetics in all cases. The pH-rate profile indicated a negligible decomposition at pH values higher than its pK(a2) value [5.40 ± 0.14 (*n = 6)]. Un-ionized 1 was subject to specific acid catalysis. The ionic strength did not affect the stability of the drug. These data can be used to develop a stable oral liquid dosage form of the drug.
Mutation of serine-39 to threonine in thermostable secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus changes enantiospecificity
Tripp, Allie E.,Burdette, Douglas S.,Zeikus, J. Gregory,Phillips, Robert S.
, p. 5137 - 5141 (1998)
The substrate specificity of wild-type and Ser39 → Thr (S39T) secondary alcohol dehydrogenase (SADH) from Thermoanaerobacter ethanolicus was examined. The S39T mutation increases activity for 2-propanol without any significant effect on NADP+ binding. There is no significant effect of the mutation on the primary and secondary alcohol specificity of SADH. However, an effect on the enantiospecificity of SADH by the S39T mutation is demonstrated. Throughout the temperature range from 15 to 55 °C, wild-type SADH exhibits a preference for (S)-2-pentanol. In contrast, a temperature- dependent reversal of enantiospecificity is observed for 2-butanol, with a racemic temperature of 297 K. Throughout the same range of temperatures, S39T SADH exhibits higher enantiospecificity for the (R)-enantiomers of both 2- butanol and 2-pentanol. Examination of individual k(cat)/K(m) values for each enantiomer of the chiral alcohols reveals that the effect of the mutation is to decrease (S)-2-butanol specificity, and to preferentially enhance (R)-2- pentanol specificity relative to (S)-2-pentanol. These results are the first step toward expanding the synthetic utility of SADH to allow efficient preparation of a range of (R)-alcohols.
Phosphomolybdic Acid as a Reoxidant in the Palladium(II)-catalysed Oxidation of But-1-ene to Butan-2-one
Davison, Suzanne F.,Mann, Brian E.,Maitlis, Peter M.
, p. 1223 - 1228 (1984)
Phosphomolybdic and a variety of phosphomolybdovanadic acids were examined as reoxidants for the palladium sulphate-catalysed oxidation of but-1-ene to butan-2-one both in the absence and the presence of oxygen.All of these co-oxidants were approximately equally effective in reoxidising Pd0 to PdII but they varied substantially in their ability to be reoxidised themselves by air under the optimum reaction conditions in aqueous acid.Phosphomolybdovanadate systems were the most effective at a pH>0, but VIV itself could not be reoxidised by air under these conditions and therefore the molybdenum must play a vital role.Phosphomolybdic acid, H3, itself was quite a good co-oxidant under more acid conditions (1 mol dm-3 sulphuric), but 31P n.m.r. spectroscopy showed that in dilute solution it was largely dissociated into phosphoric acid; evidence for the presence under some conditions of other phosphomolybdic acids, which may be related to the active species, is presented.
Isoxazoles VI: Aspects of the chemical stability of a new naphthoquinone-amine in acidic aqueous solution
Longhi,De Bertorello
, p. 754 - 757 (1990)
Some aspects of the chemical degradation of N-(3,4-dimethyl-5-isoxazolyl)-4-amino-1,2-naphthoquinone were investigated as a function of pH and temperature. In acid and neutral pH, four main degradation products were identified: 2-hydroxy-1,4-naphthoquinone, 2-butanone, ammonia, and hydroxylamine. No significant buffer effects were observed for the buffer species used in this study. The pH-rate profile exhibited a specific acid catalysis which is important at pH values 3.5, and an inflection point at pH 1.10 corresponding to a pK(a) value. From Arrhenius plots, the activation energy was found to be 17.8 ± 0.3 kcal/mol.
Syntheses of ketonated disulfide-bridged diruthenium complexes via C-H bond activation and C-S bond formation
Sugiyama, Hiroyasu,Hossain, Md. Munkir,Lin, Yong-Shou,Matsumoto, Kazuko
, p. 3948 - 3956 (2000)
The α-C-H bonds of 3-methyl-2-butanone, 3-pentanone, and 2-methyl-3-pentanone were activated on the sulfur center of the disulfide-bridged ruthenium dinuclear complex [{RuCl(P(OCH3)3)2}2(μ-S2)(μ-Cl)2] (1) in the presence of AgX (X = PF6, SbF6) with concomitant formation of C-S bonds to give the corresponding ketonated complexes [{Ru(CH3CN)2(P(OCH3)3)2}(μ-SSCHR1COR2){Ru(CH3CN)3( P(OCH3)3)2}]X3 ([5](PF6)3, R1 = H, R2 = CH(CH3)2, X = PF6; [6](PF6)3, R1 = CH3, R2 = CH2CH3, X = PF6; [7](SbF6)3, R1 = CH3, R2 = CH(CH3)2, X = SbF6). For unsymmetric ketones, the primary or the secondary carbon of the α-C-H bond, rather than the tertiary carbon, is preferentially bound to one of the two bridging sulfur atoms. The α-C-H bond of the cyclic ketone cyclohexanone was cleaved to give the complex [{Ru(CH3CN)2(P(OCH3)3)2}(μ-SS-1-cyclohexanon-2-yl){Ru(CH3CN)3(P(OC H3)3)2}](SbF6)3 ([8](SBF6)3). And the reactions of acetophenone and p-methoxyacetophenone, respectively, with the chloride-free complex [{Ru(CH3CN)3(P(OCH3)3)2}2(μ-S2)]4+ (3) gave [{Ru(CH3CN)2(P(OCH3)3)2}(μ-SSCH2COAr){Ru(CH3CN)3(P(OCH3)3)2}] (CF3SO3)3 ([9](CF3SO3)3, Ar = Ph; [10](CF3SO3)3, Ar = p-CH3OC6H4). The relative reactivities of a primary and a secondary C-H bond were clearly observed in the reaction of butanone with complex 3, which gave a mixture of two complexes, i.e., [{Ru(CH3CN)2(P(OCH3)3)2}(μ-SSCH2COCH2-CH3){Ru(CH3CN)3 (P(OCH3)3)2}](CF3SO3)3 ([11](CF3SO3)3) and [{Ru(CH3CN)2(P(OCH3)3)2} (μ-SSCHCH3COCH3){Ru(CH3CN)3(P(OCH3)3)2}](CF3SO3)3 ([12](CF3SO3)3), in a molar ratio of 1:1.8. Complex 12 was converted to 11 at room temperature if the reaction time was prolonged. The relative reactivities of the α-C-H bonds of the ketones were deduced to be in the order 2°> 1°> 3°, on the basis of the consideration of contributions from both electronic and steric effects. Additionally, the C-S bonds in the ketonated complexes were found to be cleaved easily by protonation at room temperature. The mechanism for the formation of the ketonated disulfide-bridged ruthenium dinuclear complexes is as follows: Initial coordination of the oxygen atom of the carbonyl group to the ruthenium center, followed by addition of an α-C-H bond to the disulfide bridging ligand, having S=S double-bond character, to form a C-S-S-H moiety, and finally completion of the reaction by deprotonation of the S-H bond.
Palladium Salts of Heteropolyacids as Catalysts in the Wacker Oxidation of 1-Butene
Stobbe-Kreemers, A. W.,Lans, G. van der,Makkee, M.,Scholten, J. J. F.
, p. 187 - 193 (1995)
Palladium salts of heteropolyacids (PdHPAs) of the Keggin series H3+nPVnMo12-nO40 supported on silica, have been used successfully as catalysts in the gas-phase Wacker oxidation of 1-butene.In such catalysts the palladium reaction centre and the redox component are combined in one complex.At 343 K and atmospheric pressure a high initial butanone yield of more than 0.2 g g-1cat h-1, in combination with a very high butanone selectivity of more than 98percent, can be obtained.In the steady state, the activity of the catalyst is more than a factor of 10 lower than the initial activity, due to slow reoxidation of reduced palladium-heteropolyanion complexes.The rate of reoxidation depends on the composition of the HPA, the palladium loading, and the reaction conditions.The reaction order of 0.5 in the O2 partial pressure indicates the dissociation of dioxygen to be rate determining.The degree of hydration of the HPA appears to be important for the acitivity and stability of the catalysts.Spent catalysts can be regenerated by an oxidation treatment in air at temperatures around 525 K.Regeneration becomes more difficult with high palladium loading of the catalyst.
High-turnover supramolecular catalysis by a protected ruthenium(II) complex in aqueous solution
Brown, Casey J.,Miller, Gregory M.,Johnson, Miles W.,Bergman, Robert G.,Raymond, Kenneth N.
, p. 11964 - 11966 (2011)
The design of a supramolecular catalyst capable of high-turnover catalysis is reported. A ruthenium(II) catalyst is incorporated into a water-soluble supramolecular assembly, imparting the ability to catalyze allyl alcohol isomerization. The catalyst is protected from decomposition by sequestration inside the host but retains its catalytic activity with scope governed by confinement within the host. This host-guest complex is a uniquely active supramolecular catalyst, capable of >1000 turnovers.
Greatly improved activity in ruthenium catalysed butanone synthesis
Van der Drift,Mul,Bouwman,Drent
, p. 2746 - 2747 (2001)
In situ mixing of ruthenium trichloride with one equivalent of 1,10-phenanthroline yields a highly active catalyst for synthesis of butanone from buta-1,3-diene.