Aqueous T-butyl Alcohol Research Articles

Kinetic effect of alcohols on hexose isomerization under subcritical aqueous conditions

The kinetic effect of subcritical aqueous alcohols (methanol, ethanol, 1-propanol, 2-propanol, and t-butyl alcohol) on the isomerization of hexoses (mannose, glucose, and fructose) was examined at 180°C at the alcohol concentrations ranging from 0 to 80% (v/v). The results showed that increase in the concentration of primary and secondary alcohols markedly promoted the aldose-to-ketose isomerization; however, the ketose was scarcely isomerized to aldose and predominantly decomposed. Further, the kinetic analysis revealed that the rate constants of isomerization and decomposition strongly depended on the dielectric constant of the aqueous alcohols. The rate constants for isomerization were more sensitive to the change in the dielectric constant than the decomposition rate constants. On the other hand, the isomerization reactions of mannose and fructose were suppressed in subcritical aqueous t-butyl alcohol despite the low dielectric constant of the solution.

Promotion or suppression of glucose isomerization in subcritical aqueous straight- and branched-chain alcohols.

The influence of water-miscible alcohols (methanol, 1-propanol, 2-propanol, and t-butyl alcohol) on the isomerization of glucose to fructose and mannose was investigated under subcritical aqueous conditions (180-200°C). Primary and secondary alcohols promoted the conversion and isomerization of glucose to afford fructose and mannose with high and low selectivity, respectively. On the other hand, the decomposition (side-reaction) of glucose was suppressed in the presence of the primary and secondary alcohols compared with that in subcritical water. The yield of fructose increased with increasing concentration of the primary and secondary alcohols, and the species of the primary and secondary alcohols tested had little effect on the isomerization behavior of glucose. In contrast, the isomerization of glucose was suppressed in subcritical aqueous t-butyl alcohol. Both the conversion of glucose and the yield of fructose decreased with increasing concentration of t-butyl alcohol. In addition, mannose was not detected in reactions using subcritical aqueous t-butyl alcohol.

Distinguishing aggregation from random mixing in aqueous t-butyl alcohol solutions

Raman spectroscopic measurements are combined with various multivariate curve resolution (Raman-MCR) strategies, to characterize the aggregation of t-butyl alcohol (TBA) in aqueous solutions. The resulting TBA solute-correlated (SC) spectra reveal perturbed water OH features arising from the hydration-shell of TBA as well as shifts in the TBA CH vibrational frequency arising from TBA-TBA interactions. Our results indicate that at low concentrations (below approximately 0.5 M), there is virtually no TBA aggregation. The first aggregates formed above 0.5 M remain highly hydrated, while those formed above approximately 2 M are significantly less hydrated. Comparisons with predictions pertaining to a randomly mixed (non-aggregating) solution indicate that below approximately 1 M there are fewer TBA-TBA contacts than would be present in a random mixture, thus implying that the thermodynamic stability of the first hydration-shell of TBA suppresses the formation of direct contact aggregates at low TBA concentrations. Our results further suggest that microheterogeneous domains containing many water-separated TBA-TBA contacts form near a TBA concentration of approximately 1 M, while at higher concentrations the TBA-rich domain size distribution may resemble that in a non-aggregating random mixture.

Improvement of the total turnover number and space‐time yield for chloroperoxidase catalyzed oxidation

Chloroperoxidase from Caldariomyces fumago was applied for the oxidation of indole to oxindole using hydrogen peroxide as the oxidant in aqueous t-butyl alcohol medium. Different ways of adding the oxidant, various reactor types, and the use of a hydrogen peroxide-stat were compared, resulting in a 20-fold increase of the total turnover number (ttn) and space-time yield (sty). The highest ttn of >860,000 was obtained in a fed-batch reactor, whereas the highest sty of 120 g/(L · d) was reached in a continuously operated enzyme membrane reactor. The results were compared to other enzyme systems already established for the synthesis of amino acids and carbohydrates. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 283–288, 1997.

Improvement of the total turnover number and space-time yield for chloroperoxidase catalyzed oxidation

Chloroperoxidase from Caldariomyces fumago was applied for the oxidation of indole to oxindole using hydrogen peroxide as the oxidant in aqueous t-butyl alcohol medium. Different ways of adding the oxidant, various reactor types, and the use of a hydrogen peroxide-stat were compared, resulting in a 20-fold increase of the total turnover number (ttn) and space-time yield (sty). The highest ttn of >860,000 was obtained in a fed-batch reactor, whereas the highest sty of 120 g/(L . d) was reached in a continuously operated enzyme membrane reactor. The results were compared to other enzyme systems already established for the synthesis of amino acids and carbohydrates. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 283-288, 1997.

ChemInform Abstract: Convenient Preparation of 3,3‐Dibromo‐1,3‐dihydroindol‐2‐ones and Indole‐2,3‐diones (Isatins) from Indoles.

AbstractTreatment of indole‐3‐carbaldehyde (XIII) with 3 or 4 mol NBS causes bromination of the 5‐position as well.

Convenient preparation of 3,3-dibromo-1,3-dihydroindol-2-ones and indole-2,3-diones (isatins) from indoles

3,3-Dibromo-1,3-dihydroindol-2-ones, useful precursors of Indole-2,3-diones, are readily formed by the reaction of either 3-bromoindoles or indoles with 2 or 3 mol equiv. of N-bromosuccinimide, respectively, in aqueous t-butyl alcohol. Some bromination of the 6-membered ring may occur and 3,5,6-tribromoindole-4,7-dione is a product from 3-bromo-4,7-dimethoxy-Indole. Similar reactions with Indole-3-carbaldehyde and 1H-pyrrolo[2,3-b]pyridine give 3,3-dibromo-1,3-dihydroindole-2-one and 3,3-dibromo-1H-pyrrolo[2,3-b]pyridin-2-one analogue, respectively, the latter yielding the corresponding 2,3-dione only with difficulty.

Cobalt(III)-salicaldehyde-aminophenol complexes: solubilities, transfer chemical potentials and solvation in binary aqueous solvent mixtures

Solubilities are reported for four cobalt(III) complexes of Schiff bases derived from 2-aminophenol and (substituted) salicaldehydes, in aqueous methanol, and for one of these complexes also in aqueous t-butyl alcohol and in aqueous acetone. The derived trends of transfer chemical potentials with solvent composition are discussed in relation to the nature of the ligand and the nature of the co-solvent. Solvation characteristics for the title complexes are compared with those of other inorganic complexes, particularly of cobalt(III).

Effect of solvent on the reactions of coordination complexes. Part 8.—Kinetics of solvolysis of cis-(chloro)(ethanolamine)bis(ethylenediamine)cobalt(III) in methanol–water, propan-2-ol–water and t-butyl alcohol–water

The solvolysis of cis-(chloro)(ethanolamine)bis(ethylenediamine) cobalt (III) in aqueous methanol, propan-2-ol and t-butyl alcohol results in the formation of the chelated ethanolamine complex, cis-[Co(en)2(NH2CH2CH2OH)]3+. The pseudo-first-order rate constant (ksobs) of this reaction decreases with increasing mole fraction (Xorg) of the organic cosolvent, the effect being less marked with increasing hydrophobicity of the alcohols. The plots of log ksobsvs.D–1s(Ds= bulk dielectric constant) are curved. The plots of log ksobsvs. Grunwald Winstein ‘Y’ parameter are nearly linear for CH3OH–H2O and propan-2-ol-H2O, but appreciably curved t-butyl alcohol–H2O. Under isodielectric conditions (Ds= 50) at 50 °C the plot of log ksobsvs.Xorg for CH3OH–H2O, C2H5OH–H2O, (CH3)2CH—OH–H2O, (CH3)3C—OH–H2O and (CH3)2CO–H2O in water-rich media is a straight line from which the data point for ethylene glycol–H2O (XEG= 0.36) shows positive deviation indicating its better solvating ability. The observed variation of the rate constant on solvent composition (log ksobs= log kwobs– a Xorg+bX2org) for a given aquo-organic cosolvent is interpreted in terms of a preferential solvation model. The plots of activation enthalpy and entropy vsXorg exhibit maxima and minima, thereby indicating that solvent structural changes play a significant role even for this intramolecular dissociative interchange process. The solvolysis of the complex in 99 % D2O yielded a solvent isotope effect (kH2O/kD2O= 12.6) at 50 °C, which is slightly lower than the value for several other analogous alkylamine complexes.

Solubility of Tris(acetylacetonato)chromium(III) in Aqueous Alcohol Mixtures

Abstract From the temperature dependence of the solubility of tris(acetylacetonato)chromium(III) in aqueous t-butyl alcohol mixtures and in aqueous methanol mixtures, thermodynamic parameters of the solution were calculated. The solubility and these parameters in aqueous t-butyl alcohol mixtures could be explained qualitatively by the cavity formation terms of the scaled particle theory. It was suggested that tris(acetylacetonato)chromium(III) is in water microphases at XBuOH≤0.04 and in t-butyl alcohol microphases over this region.

Oxytelluration of olefins to (β-alkoxy- and β-hydroxy-alkyl)aryltellurium dihalides and their reactions with reducing agents and aqueous NaOH

Treatment of olefinic hydrocarbons with phenyltellurium tribromide or a mixture of diphenylditelluride and bromine in alcohol affords (β-alkoxyalkyl)phenyltellurium dibromides in fair to good yield (alkoxytelluration of olefins). Various aryltellurium trichlorides, diphenylditelluride/CuCl 2, and phenyltellurocyanate/CuCl 2 can be used for the preparation of (β-alkoxyalkyl)aryltellurium dichlorides. Similar reactions in aqueous tetrahydrofuran or aqueous t-butyl alcohol result in the formation of the corresponding β-hydroxy compound (hydroxytelluration of olefins). The reaction is trans stereospecific in the cases of cis-2-butene and cis- and trans-4-octenes and regiospecific in the cases of all terminal olefins examined (1-hexene, 1-octene, 1-decene, styrene, α-methylstyrene, 2-methyl-1-pentene, and isobutylene), tellurium species attacking the terminal carbon solely. The diorganyltellurium dihalide produced is reduced to the corresponding diorganyltelluride by reducing agents such as N 2H 4, Na 2S, Na 2S 2O 3, and NaHSO 4 in aqueous solution. Treatment of the diorganyltellurium dibromide with aqueous NaOH affords either an allylic ether (by telluroxide elimination) or a telluroxide depending on the structure of the telluroxide.

Solvent effects on the kinetics of oxidation of cysteinatobis(ethylenediamine)cobalt(III) ion by peroxodisulphate

The kinetics of oxidation of cysteinatobis(ethylenediamine)cobalt(III) ion, [Co(CysOS)(en)2]+, by peroxodisulphate were investigated at different ionic strengths, adjusted with various electrolytes, and at different temperatures and concentrations of perchloric acid. Rate constants and activation parameters are also reported for this oxidation in mixtures containing up to 40% acetone, t-butyl alcohol, isopropyl alcohol, or acetonitrile. The solubilities of [Co(CysOS)(en)2]ClO4 and KClO4 have been determined in water and aqueous acetone and aqueous t-butyl alcohol at 298.2 K. From these values, Gibbs free energies of transfer for [Co(CysOS)(en)2]+ and S2O82– have been estimated. The solvent effects on the oxidation have been divided into their initial-state and transition-state components.

Effect of 1,4-Dioxane on the Structure of Aqueous t-Butyl Alcohol. Sound Velocity Studies

Abstract The structure of aqueous t-butyl alcohol in the water rich region is known to be more structured than pure water. 1,4-dioxane is known to be a weakly hydrophobic solute. The effect of 1,4-dioxane on the structure of aqueous t-butyl alcohol has been studied by fixing the temperature of sound velocity maximum in the ternary solution from the experimentally determined ultrasonic velocity data at different temperatures. The structural contribution to the shift in the temperature of sound velocity maximum of the aqueous t-butyl alcohol solution due to the addition of 1,4-dioxane, [ΔTstr.]exptl, has been found to be positive having the nature of variation similar to that of the effect of 1,4-dioxane on pure water, when the concentration (Xs) of t-butyl alcohol is 0.0075. But, for aqueous t-butyl alcohol solutions having Xs=0.0025 and Xs=0.0046, [ΔTstr.]exptl, has been found to be negative reaching maximum values around X2=0.0045 and there after decreasing with a tendency to become positive at higher concentrations of 1,4-dioxane. These results have been explained in the light of structure breaking and formation of dioxane complexes in the ternary solutions.

The mechanism of photolysis of some benzyltrimethylammonium salts in water and in alcohols

Photolysis of a range of benzyltrimethylammonium and 3,5-dimethoxybenzyltrimethylammonium salts in water or methanol at 253.7 nm gave typically benzyl alcohols (or benzyl methyl ethers), toluenes, bibenzyls and isomers, and di- and tri-methylammonium salts. By detailed sensitisation and quenching experiments it was established that, in the photolysis of benzyltrimethylammonium bromide in aqueous t-butyl alcohol, benzyl t-butyl ether, benzyl alcohol, and some toluene were produced by a singlet pathway and bibenzyl by a triplet pathway. A general mechanistic scheme for all the photolyses studied is thus suggested.

ペンタシアノコバルト（ＩＩ）酸錯体を用いたカルコン類の接触還元によるジヒドロダイマーの生成

The catalytic hydrogenation of chalcones with pentacyanocobaltate(II) afforded r-2-benzoyl, t-3, c-4-triphenylcyclopentanols, dimeric products from chalcones. The use of 50% aqueous t-butyl alcohol as a solvent and the addition of potassium hydroxide resulted in the increase of the dimeric product yields. The replacement of hydrogen at 4-position of chalcone with chlorine increased the yield of the corresponding dimeric product whereas the methoxy groupe at 4- or 4'-position of chalcone entirely suppressed the reaction.

Reactions at high pressure. Part 6. Anomalous volumes of activation, and kinetic isotope effects in the ionisation of 2-nitropropane

Rates of iodination of 2-nitropropane, catalysed by 2,4,6-trimethylpyridine have been measured in aqueous t-butyl alcohol at 25° at pressures of 1–1 285 bar and similarly for 2-nitro[2-2H]propane. It is found that oxygen affects the measured rates and, if the reaction is carried out under nitrogen, rates are faster and the kinetic isotope effect, kH/kD 16, less than previously reported. There is still a large tunnelling contribution and this is found to be pressure dependent, tending towards 7. The volumes of activation for 1H and 2H compounds are different, –31 and –40 cm3 mol–1 respectively; it is believed the former is anomalous. The large negative value of ΔV0‡ is consistent with a high degree of proton transfer and almost maximum charge development in the transition state.

Lumry's law and the quenching of anthracene fluorescence by bromide in aqueoust-butyl alcohol

The Stern-Volmer quenching constant for the quenching of anthracene fluorescence by bromide at 298.15 K shows a complex dependence on alcohol mole fraction in water plust-butyl alcohol mixtures. A similar pattern is observed at other temperatures except near 285 K, the Lumry temperature for aqueous systems.

Mechanism of photolysis of benzyltrimethylammonium salts in hydroxylic solvents

Photolysis of benzyltrimethylammonium bromide in aqueous t-butyl alcohol gives benzyl t-butyl ether and some toluene by a singlet pathway with more toluene and bibenzyl by a triplet pathway, in each case via a reactive intermediate geminate pair (or pairs); analogous mechanisms are suggested for photolysis of a range of benzyltrimethylammonium salts in water or methanol.

ChemInform Abstract: SOLVATION SPECTRA PART 44, NUCLEAR MAGNETIC RESONANCE STUDY OF BINARY SOLVENT MIXTURES, WATER STRUCTURAL EFFECTS

The hydroxyl proton resonance frequency for various binary solvent mixtures, including water with methanol, t-butyl alcohol, triethylamine and acetone, has been measured over the complete mole fraction range. Results of similar experiments for alcohol + alcohol and alcohol + amine mixtures are used for comparative purposes. At low concentrations water behaves normally in these solvents, but in the water-rich region shifts to low-field were generally observed, especially for aqueous alcohols and amines. These are interpreted in terms of an acid-base effect, and an effect involving local changes in water structure, equivalent to a temperature reduction. Various methods for differentiating between these two factors are outlined. It is concluded that for aqueous methanol, the acid-base effect dominates, whilst for aqueous t-butyl alcohol the water-structure effect is of major significance. Other solvents fit between these extremes.

The formation of (CH 3) 3Ċ, H 2ĊC(Me) 2OH and ĊH 3 radicals in the radiolysis of aqueous t-butyl alcohol: on the solvation of t-butyl alcohol by water

Exposure of aqueous glassy solutions of t-butyl alcohol to 60Co γ-rays at 77°K gave ESR spectra characteristic of Me 3Ċ, and H 2ĊC(Me) 2OH radicals. The results for the former were unusual in that, for very dilute aqueous solutions and for solutions of 0.4 mole fraction through to the pure alcohol, all the Me 3Ċ radicals were apparently freely rotating, whilst for solutions in the mole fraction region 0.05 to 0.4, some or all of these radicals were stationary. Implications with respect to water structural factors are discussed.