Solutions Of Tert-butanol Research Articles

Compressibilities of aqueous tert-butanol in the water-rich region at 25°C: Partial molar fluctuations and mixing schemes

We measured the speeds of sound, u, and the densities, d, and, hence, determined the adiabatic compressibilities, κS, of aqueous tert-butanol (TBA) at small increments in mole fraction of TBA, xTBA. Existing data for heat capacity, Cp, and thermal expansivity, αp, were used to convert κS to the isothermal compressibilities, κT. Using these κT data, the normalized volume fluctuations, VΔ, and their composition derivative, the partial molar volume fluctuations of TBA, VΔTBA, (Y. Koga and P. Westh, Bull. Chem. Soc. Jpn., 1996, 69, 1505) were calculated. By using Cp data available in the literature we also calculated the normalized entropy fluctuations, SΔ, and the partial molar entropy fluctuations of TBA, SΔTBA. Furthermore, the density data at 15, 25 and 35°C in the literature were used to evaluate the thermal expansivities, αp, from which the normalized cross (entropy–volume) fluctuations, SVΔ, and the partial molar cross-fluctuations of TBA, SVΔTBA, were calculated. The composition dependence of these fluctuation functions were interpreted in the light of the mixing schemes in aqueous solutions of TBA and other non-electrolytes and the transition between them (Y. Koga, J. Phys. Chem., 1996, 100, 5172).

Dissociation constants of methyl orange in aqueous alcohol solvents

The dissociation constants of methyl orange (H +In −) has been determined at 25°C and an ionic strength of 0.1 mol l −1 in water and in mixed aqueous solutions of methanol (10–90 wt%), ethanol (10–70 wt%), iso-propanol (10–60 wt%) and tert-butanol (10–50 wt%) by spectrophotometric measurements. It has been shown that the solvents affect the acid–base equilibria, visible absorption spectra and color transition range of methyl orange to different extents. The p K a values decrease with increasing composition of the co-solvent in the order: tert-butanol>iso-propanol>ethanol>methanol>water. A linear relationship between p K a and the mole fraction of the co-solvent was observed in a limited range of the compositions for each of the solvent systems. The results have been discussed in terms of the standard Gibbs energies of transfer of H +, Δ G 0 t (H +), and the relative values of Δ G 0 t(In −) and Δ G 0 t(H +In −) in all solvent systems.

Fluctuations in aqueous solutions of some hydrophobic solutes

The entropy fluctuation in liquids and solutions is most conveniently normalzied to the coarse-grained volume. Hence, 〈(ΔS/V) 2〉 = RC p/V m 2 and 〈ΔS/V)(ΔN/N)〉 = RTα p/V m . It is shown to be useful if the response functions, C p , χ T and α p , and the fluctuations derived from them, were discussed separately in contrasting the peculiar nature of liquid H 2O against a typical van der Waals liquid, benzene. The composition dependence of these fluctuations was examined in aqueous solutions of typical hydrophobic solutes, 2-butoxyethanol, 2-butanone and tert-butanol. It was concluded that the above solutes reduce the hydrogen bond probability in H 2O up to the crossover point of mixing scheme, x i c .

Determination of stability constants of copper(II) complex of glycine in water + alcohol mixed solvents with ion selective electrode technique

The first stability constants (log β 1) of the copper(II) complex of glycine in water and in 13 water + alcohol (isopropanol, tert-butanol, 1,2-propylene glycol and glycerol) solvents have been determined at 25°C and an ionic strength of 0.10, from pH and pCu measurements of cells containing copper(II) ion selective electrode. It has been shown that as the proportion of the alcohol increases, the stability constants become increasing positive in all of the mixed solvents examined. An almost linear relation between log β 1 and the mole fraction of alcohol was found for the complex in aqueous solutions of isopropanol, tert-butanol and glycerol. The response of the copper(II) ion selective electrode in water and in water + alcohol mixed solvents was also investigated. The advantages of using an ion selective electrode to determine the stability constants in mixed solvents are discussed.

Millimeter spectroscopic study of intermolecular interactions in solutions

The absorption of 5 cm−1 electromagnetic radiation by aqueous solutions of methyl, ethyl, n-, and isopropyl, sec-, iso-, and tert-butyl, and tert-amyl alcohols and ethylene glycol was measured within their solubility limits in water at 20°C. It was found that the observed nonadditivity of absorption (absorption deficit) is a qualitative measure of hydration of alcohols of two types: hydrophilic and hydrophobic. The possibility of distinguishing these effects by millimeter spectroscopy was demonstrated. Hydrophobic hydration makes the basic contribution to the hydration number of aliphatic alcohols. On the example of solutions of ethanol and tert-butanol, it was shown that hydrophobic hydration decreases with an increase in the temperature of the solution due to intensification of hydrophobic interactions between the hydrocarbon radicals.

NMR chemical shifts of xenon in aqueous solutions of amphiphiles: A new probe of the hydrophobic environment

The chemical shift of elemental xenon in solution is sensitive to the environment. The shift arises from van der Waals interactions in most liquids, but an additional effect is present in aqueous media yielding a larger shift than expected. In water the shift is affected by the presence of low molecular weight amphiphiles, and its variation with composition can reveal the presence of hydrophobic hydration of the amphiphile. The results are similar to the conclusions drawn from other physical studies. Data are presented for aqueous solutions of methanol, ethanol, n-propanol, iso-propanol, tert-butanol, dimethylsulfoxide, p-dioxane, and acetonitrile.

Concerning 1e- transfer in reduction by dihydronicotinamide: reaction of oxidized flavin and flavin radical with N-benzyl-1,5-dihydronicotinamide.

The rates of reaction of 5-ethyl-3-methyllumiflavinium perchlorate and 5-ethyl-3-methyllumiflavinyl radical with a NADH analogue, N-benzyl-1,4-dihydronicotinamide, were measured anaerobically in tert-butanol and 5% acetonitrile/95% tert-butanol solutions at 30 degrees C. The biphasic kinetics observed for the reaction of flavin radical with dihydronicotinamide were interpreted in terms of both a 1e- and a 2e- mechanism; the former was found to be inadequate based on experimental requirements of the mechanism. The dihydronicotinamide reacts preferentially with oxidized flavin rather than flavin radical, even when the concentration of oxidized flavin is at a concentration 5 orders of magnitude less than that of radical. These studies show that the "hydride" reduction of oxidized flavin by BNAH is more facile than is the 1e- reduction of flavin radical by BNAH.

Zur Kinetik der Isobutenhydratation in Schwefels�ure-Wasser?t-Butanoll�sungen

The reaction rate constants of the hydratization of isobutene in aqueous sulfuric acid—tert-butanol solutions can be correlated with theHammett acidity function. The activity energy depends on the concentration oftert-butanol. On the basis of the given correlation it is possible to extrapolate reaction rate constants beyond the kinetic regime of the isobutene hydratization.

Isentropic compressibilities of alcohol-water mixtures at 25�C

The sound velocities of aqueous solutions of methanol, ethanol, 2-propanol, tertbutanol and 2-butoxyethanol (BE) were measured over the whole mole fraction range at 25°C. The isentropic apparent and partial molar compressibilities, φK,S and φS,A were derived from these data. In the case ofBE, the isothermal partial molar compressibilities were also calculated. φK,S and φS,A for all alcohols except BE initially decrease slightly with the mole fraction and then increase sharply, especially with the higher members, to the value of the pure liquid. In the case of BE, φK,S and φS,A do not go through an initial minimum and the latter goes through a sharp maximum. The compressibilities of water in these mixtures are significantly lower than those of pure water itself. These data can be correlated with other properties and are consistent with the existence of microphase transitions in these aqueous organic mixtures.

A pulse radiolysis study of solvated electrons in dilute solutions of polar liquids in nonpolar solvents

Measurements of the conductivities following electron pulse irradiation of dilute solutions of ethanol, n-propanol, tert-butanol, or dimethyl sulphoxide in n-hexane, cyclohexane, or i-octane are quantitatively consistent with the existence of equilibria between electrons in the hydrocarbon and electrons solvated by dimers of the polar molecules. With dimethylformamide solutions in alkanes the equilibrium could be with the monomeric anion of the solute but this assignment is not unequivocal. Absorption spectra of es− in n-hexane solutions of ethanol and of tert-butanol have been obtained.