Aqueous Solutions Of Tert-butyl Alcohol Research Articles

Quantifying the Nearly Random Microheterogeneity of Aqueous tert-Butyl Alcohol Solutions Using Vibrational Spectroscopy.

The microheterogeneous structure of aqueous tert-butyl alcohol (TBA) solutions is quantified by combining experimental, simulations, and theoretical results. Experimental Raman multivariate curve resolution (Raman-MCR) C-H frequency shift measurements are compared with predictions obtained using combined quantum mechanical and effective fragment potential (QM/EFP) calculations, as well as with molecular dynamics (MD), random mixture (RM), and finite lattice (FL) predictions. The results indicate that the microheterogeneous aggregation in aqueous TBA solutions is slightly less than that predicted by MD simulations performed using either CHARMM generalized force field (CGenFF) or optimized parameters for liquid simulations all atom (OPLS-AA) force fields but slightly more than that in a self-avoiding RM of TBA-like molecules. The results imply that the onset of microheterogeneity in aqueous solutions occurs when solute contact free energies are about an order of magnitude smaller than thermal fluctuations, thus suggesting a fundamental bound of relevance to biological self-assembly.

How Different Are the Characteristics of Aqueous Solutions of tert-Butyl Alcohol and Trimethylamine- N-Oxide? A Molecular Dynamics Simulation Study.

Atomistic molecular dynamics simulations have been used to investigate differences in the characteristics of the aqueous solutions of two structurally similar, biologically important molecules, namely, tert-butyl alcohol (TBA) and trimethylamine- N-oxide (TMAO). By analyzing radial distribution functions, preferential solvation factors, and the number of nearest neighbors, structural characteristics of the two aqueous solutions are found to be dramatically different. By examining the distribution of nearest neighbor solute and solvent molecules in these two solutions, it is found that the aqueous solution of TMAO is homogeneous, whereas that of TBA is not. Further scrutiny of TBA-TBA radial distribution function at a high concentration by splitting the surrounding TBA molecules into two hemispheres demonstrates that the TBA aggregation occurs not only from the side of methyl moieties of TBA as expected in hydrophobicity-induced aggregation, but also from the side of the polar C-OH group. To analyze the effect of concentration of the two solute molecules (TBA and TMAO) on the local structure of water, tetrahedral order parameter and distributions of tetrahedral angles and hydrogen-bonding angles have been calculated for both the solutions. It is surprising to see that at high concentrations, the local water structure in the TMAO solution is more disrupted compared to the same in the TBA solution. Finally, the action of these two solutes on the folding-unfolding behavior of Trp-cage miniprotein has been analyzed and their contrasting activities toward the protein stability are correlated to the strikingly different behavior of their aqueous solutions.

Routes to Alkene and Epoxide Functionalized Nanoporous Materials from Poly(styrene-b-isoprene-b-lactide) Triblock Copolymers

Nanoporous materials with inherently tunable surface chemistries are poised to have a considerable impact in catalysis, separations, and nanopatterning. Using core−shell cylinder forming polystyrene-b-polyisoprene-b-polylactide (PS−PI−PLA) triblock terpolymers as templates, we were able to prepare aligned PI-coated nanoporous PS monoliths via the degradative removal of the cylindrical PLA cores. PS−PI−PLA precursors were synthesized using a combination of anionic (PS, PI) and ring-opening (PLA) polymerizations. The degree of order, alignment, and PLA degradation achievable was a strong function of molecular weight at a given triblock terpolymer composition. For intermediate molecular weight samples (25−28 kg mol-1), greater than 95% of the PLA was hydrolyzed through exposure of the monolith to a 0.1 wt % sodium dodecyl sulfate (SDS) solution in 0.5 N NaOH. However, low (17.5 kg mol-1) and high (46.8 kg mol-1) molecular weight samples of identical composition showed considerable resistance to PLA degradation. Treatment of the degraded monoliths with m-chloroperoxybenzoic acid in aqueous tert-butyl alcohol solutions permitted the controlled epoxidation of up to 75−80% of the PI alkene units. Despite some loss in pore alignment, scanning electron microscopy and small-angle X-ray scattering verified the retainment of the nanoporous structure following epoxidation.

Determination of Temperatures within Acoustically Generated Bubbles in Aqueous Solutions at Different Ultrasound Frequencies

Mean acoustic bubble temperatures have been measured using a methyl radical recombination (MRR) method, at three ultrasound frequencies (20, 355, and 1056 kHz) in aqueous tert-butyl alcohol solutions (0-0.5 M). The method is based on yield measurements of some of the hydrocarbon products formed from the recombination of methyl radicals that are thermally generated within collapsing bubbles containing tert-butyl alcohol vapor. The mean bubble temperatures were found to decrease substantially with increasing tert-butyl alcohol concentration at 355 and 1056 kHz but only to a small extent at 20 kHz. Extrapolating the mean temperatures measured to zero concentration of tert-butyl alcohol, at a bulk solution temperature of 20 degrees C, gave the order 355 kHz (4300 +/- 200 K) > 1056 kHz (3700 +/- 200 K) > 20 kHz (3400 +/- 200 K). It is also concluded that the temperature derived from the MRR method is a useful diagnostic parameter for sensing the thermal conditions within an active acoustic bubble. However, attention must be given to the fact that the temperature derived from the MRR method is not theoretically well defined.

Adiabatic compressibility of pseudo-binary aqueous solutions of tert-butyl alcohol and dimethylsulfoxide as a result of ultrasonic investigations

The tert-butyl alcohol (TBA) and dimethyl sulfoxide (DMSO) are two small molecules geometrically very similar, but having different polar groups. Taking into account the intermolecular interactions in the TBA/H 2O and DMSO/H 2O systems, especially in the water-rich region of concentration, the ultrasonic speeds (high accuracy resonance method at the frequency 7.5 MHz) and densities in pseudo-binary mixtures of the system: (TBA + H 2O + DMSO) with the ratio (TBA + DMSO)/H 2O = 1/25 have been measured. From these data, various thermodynamical parameters such as adiabatic compressibility, molar volume, thermal expansivity, and the deviation from reference system have been calculated. In addition, the isobaric molar heat capacity to convert adiabatic compressibility to the isothermal one has been measured. All these parameters have been discussed to explain solute–solvent and solute–solute interactions, especially the effect of the complexation process between TBA and DMSO molecules. The composition dependence of these deviations functions was interpreted in the light of the mixing schemes in the aqueous solutions of TBA and DMSO.

Hydrogen Bonding of Water in Aqueous Solutions of Trimethylamine-N-oxide and tert-Butyl Alcohol: A Near-Infrared Spectroscopy Study

The hydration properties of two biologically relevant molecules, trimethylamine-N-oxide (TMAO) and tert-butyl alcohol (TBA), were investigated by monitoring the effects of these two solutes on the near-infrared (NIR) spectra of water. In particular, the 1450-nm ν1 + ν3 water combination band (ν1 is the symmetric stretching and ν3 is the asymmetric stretching) and the 1928-nm ν2 + ν3 band (ν2 is the bending) were recorded at 25 °C in aqueous solutions of TBA and TMAO over the 0−0.1 and 0−0.05 solute mole fraction intervals for TBA and TMAO, respectively. NIR data show, in agreement with molecular dynamics simulations and other suggestions found in the literature, that on the whole water molecules are more tightly coordinated by TMAO than by TBA. Furthermore, nonadditive perturbations of the water's H-bond network are observed for TBA and are absent in the TMAO case. These results are discussed in connection to the significantly different action exerted by these two solutes on typical processes governed by hydrophobic interactions, such as protein folding and micellization of a surfactant. In these processes, the data support the assumption that the presence of TMAO or TBA modifies the extent of the free-energy contribution associated with structural reorganization of water.

Interfacial Properties of tert-Butyl Alcohol Solutions and Their Relation to Clathrate Formation

According to a previous report (Glinski, J.; et al. J. Chem. Phys. 1996, 102, 8816) the surface entropy of the tert-butyl alcohol/water system shows a maximum with respect to solute concentration. Such a maximum was formerly related to the formation of clathrate structures at the interfacial region. However, more complex behavior has also been observed in other aqueous systems. It is currently believed that the surface entropy maxima may reflect structural changes similar to a phase transition and specific interactions between solute molecules. To test the clathrate hypothesis, the thermodynamic properties of tert-butyl alcohol at water, heptane, and water/heptane interfaces were evaluated. For this purpose, the variation of the surface/interfacial tension as a function of temperature and solute concentration was measured, employing Wilhelmy plate and Du Nouy ring techniques. In aqueous tert-butyl alcohol solutions, the maximum of entropy found by Glinski et al. is reproduced. The absence of a large maxim...

Hydrophobic hydration and hydrophobic interaction in aqueous solutions of tert-butyl alcohol and trimethylamine-N-oxide: a correlation with the effect of these two solutes on the micellization process

We report the study of the effect of tert-butyl alcohol (TBA) and trimethylamine-N-oxide (TMAO) on a typical process governed by the hydrophobic interaction, such as the micellization of a surfactant in aqueous solution. The behaviour of the critical micelle concentration (c.m.c.) of the sodium dodecyl sulfate (SDS) was investigated as a function of the added amounts of TBA or TMAO by conductivity measurements. The hydration properties of the two solutes was studied by IR spectroscopy, in the region of the frequency of the O–H stretching band for H2O and of the methylic band for TBA and TMAO. The overall behaviour of the TBA/H2O and TMAO/H2O solutions is also studied by compressibility measurements. The data were discussed in terms of the hydration properties of TBA and TMAO and of the thermodynamical properties of the mixtures. Significant correlations between these properties and the effect of TBA and TMAO on the micellization process are shown.

Positron annihilation in and compressibility of liquid water + tert-butyl alcohol mixtures

Abstract Aqueous solutions of tert-butyl alcohol (2-methyl-2-propanol) were investigated using sound velocity and positron annihilation methods. The results are interpreted in terms of changing the structure of the solution, especially the formation of clathrate-like hydrates. The annihilation method was found to be applicable for investigating the structure of aqueous solutions of nonelectrolytes; the lifetime and intensity of the long-lived component of the annihilation spectrum were found to be sensitive for structural rearrangements in liquid.

Structure of liquid mixtures studied by positron annihilation and sound velocity: Water+tert-butanol

Aqueous solutions of tert-butyl alcohol (2-methyl-2-propanol) were investigated using sound velocity and positron annihilation methods. The results are interpreted in terms of changing structure of solution, especially formation of clathrate-like hydrates. The annihilation method was found to be applicable for investigating the structure of aqueous solutions of non-electrolytes. Resolution of annihilation spectrum into three components (instead of two) yield non-physical parameters, suggesting that the short-lived mechanisms of annihilation of positrons are too close to be separated.

Viscosities of aqueous tert-butyl alcohol solutions

The kinematic viscosities of dilute aqueous solutions of tert-butyl alcohol, for concentrations of 0-2.5 kmol/m 3 and temperatures from 303.15 to 333.15 K, have been measured. Use is made of the Eyring equation to correlate kinematic viscosities with the alcohol mole fraction and temperature. Enthalpies and entropies of activation for viscous flow, needed in the Eyring equation, are also provided. These correlate linearly with composition

Excess partial molar free energies and entropies in aqueous tert-butyl alcohol solutions at 25.degree.C

Excess partial molar free energies and entropies in aqueous tert-butyl alcohol solutions at 25.degree.C

Enthalpies and heat capacities of transfer of sodium carboxylates and sodium dodecylsulfate from water to aqueoustert-butyl alcohol solutions

Integral enthalpies of solution at very low concentrations of sodium carboxylates and sodium dodecylsulfate in aqueous tert-butyl alcohol solutions at 25°C and 35°C were measured with an isoperibol submarine calorimeter. The enthalpies and heat capacities of transfer of these surfactants from water to aqueous tertbutyl alcohol solutions were derived from integral enthalpies of solution. The results are explained in terms of the structural alteration effect of the constituent hydrophobic and hydrophilic groups of the solute.

Volume Properties of Aqueous Solutions of tert-Butyl Alcohol at Temperatures between 5 and 25 degrees C.

Volume Properties of Aqueous Solutions of tert-Butyl Alcohol at Temperatures between 5 and 25 degrees C.