Pure 2-propanol Research Articles

Determination of refractive indices of liquids by Fresnel diffraction

We demonstrate an easy, reliable, applicable, and sensitive method to measure refractive index of liquids by using Fresnel diffraction. In this method a cylindrical glass rod, in general, or an optical fiber in special case, is immersed into a liquid. Physical parameters of the rod, like radius and refractive index, should be well known. Then, the normalized intensity distribution on the Fresnel diffraction pattern of a plane wave diffracted from the immersed fiber is measured. Thereafter, refractive index of the liquid is evolved by the least-square method. This method applied to determine the refractive index of four liquids; pure water, 2-propanol (isopropanol), acetone and methanol. Index of refraction of each one has been acquired for four visible wavelengths. A theoretical approach and experimental results is presented.

Compressed and Saturated Liquid Densities for the 2-Propanol + Water System

Compressed liquid densities for the 2-propanol (1) + water (2) mixture have been determined at (300, 325, and 350) K and x1 close to 0.25, 0.49, and 0.73 using a vibrating tube densimeter. Liquid densities have been measured from about atmospheric pressure up to 10 MPa and correlated with a multilayer feedforward neural network. The composition dependence of the excess molar volume has been evaluated in the temperature and pressure range of the experimental data. A model based on a multilayer feedforward neural network function combined with the saturated pressure equation of the pure fluids has been regressed on the available literature data for the bubble pressure. The correlations for liquid density and bubble pressure have been used to generate the saturated liquid density surface in the whole temperature range of the measured compressed liquid densities and for compositions ranging from the pure 2-propanol to the pure water.

Solubility of Losartan Potassium in Different Pure Solvents from (293.15 to 343.15) K

The solubility of 2-butyl-4-chloro-1-[[2′-tetrazol-5-yl)-biphenyl]-4-yl]methyl-5-(hydroxymethyl) imidazole potassium in pure methanol, ethanol, 1-propanol, 2-propanol, 1-pentanol, ethyl acetate, butyl acetate, and cyclohexane was measured by a synthetic method over the temperature range from (293.15 to 343.15) K under atmospheric pressure. The experimental data were correlated by the modified Apelblat model. The results show that the solubility of losartan potassium increases with the increasing temperature in pure methanol, ethanol, 1-propanol, and 2-propanol and decreases with the increasing temperature in 1-pentanol. It is also found that losartan potassium is sparingly soluble in ethyl acetate, butyl acetate, and cyclohexane, and the solubility in these three solvents varys little with the temperature.

The Influence of Mobile Phase Demixion on Thin-Layer Chromatographic Enantioseparation of Ibuprofen and Naproxen

In our earlier article we presented the results of tracing the enantioseparation of the two test analytes (ibuprofen and naproxen) by means of video densitometry and scanning densitometry. In that way we demonstrated an excellent performance of this combined approach to the thin-layer chromatographic detection in the area of enantioseparation. In this paper we study an impact of the four different mobile phases on the enantioseparation of the scalemic mixtures of ibuprofen and naproxen on the silica gel layers impregnated with L-arginine as chiral selector. The main component of all the investigated mobile phases is 2-propanol. Mobile phase 1 consists of pure 2-propanol, while mobile phases 2-4 contain, respectively, ca. 0.66, 1.32, and 1.98 g/L of glacial acetic acid in 2-propanol. Acetic acid is used to protonate L-arginine, as the involved retention mechanism consists of the ion pair formation between L-arginine in the cationic form and the chiral 2-arylpropionic acids (2-APAs), ibuprofen and naproxen, in the anionic form. It is shown that in the absence of glacial acetic acid no enantioseparation can be obtained. Then with adding of 0.66 g/L glacial acetic acid partial enantioseparation of the naproxen and ibuprofen antimers is obtained, with a simultaneous effect of the mobile phase demixion. With the amount of acetic acid increasing, the effect of demixion becomes increasingly perceptible. In that case the displacement effect is observed (and mathematically modeled), which results in compressing of the antimer pairs by the second front of mobile phase. The obtained results allow a deeper insight into the mechanism of enantioseparation with the two test 2-APAs. A combined impact of the crystalline chirality of silica gel and the molecular chirality of L-arginine on the vertical and the horizontal enantioseparation of ibuprofen and naproxen is also discussed.

Mixtures of methanol and 2-propanol as a potential fuel for direct alcohol fuel cells

The electrochemical oxidation of methanol, 2-propanol, and their mixtures was investigated on a Pt/C thin film electrode in acid solution. It was confirmed that the oxidation of 2-propanol commences at less positive potentials than that of methanol and exhibits significantly higher oxidation current densities at low potentials. When both methanol and 2-propanol were present in the solution, the onset of the oxidation current was the same as for the oxidation of pure 2-propanol. Although both alcohols inhibit the oxidation reaction of each other to a certain extent, steady-state polarization measurements showed that their mixture provides higher current densities than single alcohols over the entire potential region from the hydrogen region to oxide formation on the Pt surface. This implies that the addition of 2-propanol into the fuel may extend the operational range of direct methanol fuel cells.

Direct HPLC enantioseparation of chiral aptazepine derivatives on coated and immobilized polysaccharide‐based chiral stationary phases

The direct HPLC enantioseparation of Mianserin and a series of aptazepine derivatives is accomplished on polysaccharide-based chiral stationary phases (CSPs). The resolutions are performed on the coated-type Chiralcel OD and Chiralpak AD CSPs and on the first commercially available immobilized-type Chiralpak IA CSP, in normal-phase and polar-organic modes. The complete separation of enantiomers of all racemates investigated was successfully achieved under at least one of CSP/eluent combinations employed. Pure alcohols such ethanol or 2-propanol, with a fixed percentage of DEA added, serve as valuable alternatives to the more common n-hexane-based normal-phase eluents in resolution of Mianserin on the AD CSP. In order to study the chiroptical properties of aptazepine derivatives, chromatographic resolutions are carried out at semipreparative scale using Chiralpak AD and Chiralpak IA as CSPs. Nonconventional dichloromethane-based eluents have permitted to expand the chiral resolving ability of the immobilized Chiralpak IA CSP and to perform mg-scale enantioseparations with an analytical-size column. Assignment of the absolute configuration of the separated enantiomers is empirically established by comparing their chiroptical data with those of structurally related Mianserin.

Surfaces of Alcohol−Water Mixtures Studied by Sum-Frequency Generation Vibrational Spectroscopy

Sum-frequency generation vibrational spectroscopy was used to investigate the surface molecular structure of binary mixtures of water and alcohol (methanol, ethanol, and propanol) at the air/liquid interface. In this study, it is shown that the sum-frequency signal from the alcohol molecules in the CH-stretch vibration region is always larger for mixtures than that from pure alcohol. For example, the sum-frequency signal from a propanol mixture surface at a 0.1 bulk mole fraction was approximately 3 times larger than that from a pure propanol surface. However, the ratio between the sum-frequency signals taken at different polarization combinations was found to be constant within experimental errors as the bulk alcohol concentration was changed. This suggested that the orientation of surface alcohol molecules does not vary appreciably with the change of concentration and that the origin of the signal enhancement is mainly due to the increase in the surface number density of alcohol molecules contributing to the sum-frequency signal for the alcohol/water mixture as compared to the pure alcohol surface.

Pervaporation from a Dense Membrane: Roles of Permeant−Membrane Interactions, Kelvin Effect, and Membrane Swelling

Dense polymeric membranes with extremely small pores in the form of free volume are used widely in the pervaporative separation of liquid mixtures. The membrane permeation of a component followed by its vaporization on the opposite face is governed by the solubility and downstream pressure. We measured the evaporative flux of pure methanol and 2-propanol using dense membranes with different free volumes and different affinities (wettabilities and solubilities) for the permeant. Interestingly, the evaporative flux for different membranes vanished substantially (10-75%) below the equilibrium vapor pressure in the bulk. The discrepancy was larger for a smaller pore size and for more wettable membranes (higher positive spreading coefficients). This observation, which cannot be explained by the existing (mostly solution-diffusion type) models ofpervaporation, suggests an important role for the membrane-permeant interactions in nanopores that can lower the equilibrium vapor pressure. The pore sizes, as estimated from the positron annihilation, ranged from 0.2 to 0.6 nm for the dry membranes. Solubilities of methanol in different composite membranes were estimated from the Flory-Huggins theory. The interaction parameter was obtained from the surface properties measured by the contact angle goniometry in conjunction with the acid-base theory of polar surface interactions. For the membranes examined, the increase in the "wet" pore volume due to membrane swelling correlates almost linearly with the solubility of methanol in these membranes. Indeed, the observations are found to be consistent with the lowering of the equilibrium vapor pressure on the basis of the Kelvin equation. Thus, a higher solubility or selectivity of a membrane also implies stronger permeant-membrane interactions and a greater retention of the permeant by the membrane, thus decreasing its evaporative flux. This observation has important implications for the interpretation of existing experiments and in the separation of liquid mixtures by pervaporation.

Measurement and modeling of the equilibrium behavior of the Tröger’s base enantiomers on an amylose-based chiral stationary phase

The binary isotherms of the two enantiomers of Tröger’s base were measured on a system made of pure 2-propanol as the mobile phase and of Chiralpak AD, a chiral stationary phase (CSP) based on amylose tri-(3,5-dimethylphenyl carbamate). The experimental data were acquired using both frontal analysis and the perturbation method. The results obtained are most unusual. The adsorption of the more-retained (−)-enantiomer is not competitive: the amount adsorbed onto the CSP at equilibrium with a constant concentration of the (−)-enantiomer is independent of the concentration of the (+) enantiomer. On the other hand, the adsorption of the less-retained enantiomer is cooperative: the amount of this (+)-enantiomer adsorbed by the CSP at equilibrium with a constant concentration of this enantiomer increases with increasing concentration of the (−)-enantiomer. Such a phenomenon has hardly ever been reported. A model equation is proposed that accounts well for all these isotherm data.

The ion exchange equilibria of Na +/K + in nonaqueous and mixed solvents on a strong acid cation exchanger

Na +/K equilibrium ion exchange isotherms on Amberlite IR-120 (known as a strong acid resin) in pure methanol, ethanol, 2-propanol, 1-butanol and 1-penthanol and in mixtures of methanol+water, ethanol+water, 2-propanol+water, 1-butanol+methanol and 1-penthanol+methanol at 313 K have been determined. In this paper two models for the description of ion exchange equilibrium in nonaqueous media are compared: the heterogeneous model (HMAM), based on the mass action law in which ideal behaviour for both the solution and the solid phase and the heterogeneity of ion exchange sites has been assumed and the homogeneous model (LAM), based on the same mass action law in which nonideal behaviour for both the solution and the solid phase has been taken into account. In the LAM model, Wilson and Debye–Hückel equations have been used to calculate activity coefficients in the solid and the liquid phase, respectively. It has been observed that the properties of the solvents that compound the solution phase exerts a strong influence not only on the useful capacity of the resin, but also on the equilibrium parameters of the system. This influence can be, at least, qualitatively explained based on the changes of dielectric constant of the liquid phase and on the solvation of ions. For systems with a behaviour close to ideality, the HMAM model shows that the energy distribution was practically symmetric, with similar equilibrium constants for both kinds of sites. In those systems with a behaviour far from the ideality, the energy distribution is clearly asymmetric.

Effects of ions on the dielectric permittivity and relaxation rate and the decoupling of ionic diffusion from dielectric relaxation in supercooled liquid and glassy 1-propanol

The effects of intermolecular H bonds on the equilibrium permittivity, εs, the relaxation rate, fm, and changes in the dielectric relaxation spectra of 1-propanol were studied by adding a strongly dissociating electrolyte LiClO4. The spectra of both 1 mol % LiClO4 containing 1-propanol (1 molecule of LiClO4 per 99 molecules of 1-propanol), and of pure 1-propanol were measured over a temperature range from ∼90–160 K in the frequency range 1 mHz–1 MHz. An analysis of the spectra showed that the three relaxation processes (I, II, and III in ascending rapidity), that occur in the pure alcohol persist in the presence of ions, the equilibrium permittivity, εs, decreases, the distribution characteristics of the processes changes, and the rate of relaxation, fm, of processes I and III remains constant within analytical errors, while that of process II is reduced. The temperature dependencies of fm,I and fm,II are non-Arrhenius while that of fm,III is Arrhenius. The temperature dependence of the dc conductivity, σ0 is also non-Arrhenius, but the parameters of the fit differ from those of fm,I and are closer to those of fm,II. Its 1000-fold increase on adding 1 mol % LiClO4 is due to the increase in ion concentration and a decrease in the viscosity as a result of the breaking of H bonds. However, as fm,I and fm,III remain constant on the addition of LiClO4, and fm,II decreases slightly, an expected decrease in viscosity would seem to be unrelated to the relaxation rates of these processes. In that case, σ0 is decoupled from these dipolar relaxation modes.

1-Propanol hydrate by IR spectroscopy

The mid-IR attenuated total reflectance (mid-IR–ATR) spectra of a series of 1-propanol and water mixtures were obtained. Factor analysis (FA) applied to spectra gave the spectra of three principal species and their abundance: pure water, pure propanol, and a 1-propanol hydrate (1:1). When compared to the pure solvents, the hydrate propanol bands were modified which indicated that the valence bonds were perturbed. The assignment of the hydrate IR bands was made by comparing them with those of pure 1-propanol and pure water. No monomer was observed which indicated that all species were associated. The simplest representation of the different associations is by groups of two on which an intermolecular bond (H-bond) can be placed. The exchange between the molecules can be represented by the following equation: (H2O···H2O) + (CH3CH2CH2OH···OHCH2CH2CH3) [Formula: see text] 2(CH3CH2CH2OH···OH2). The hydrate's formation constant (Kf) is 1.2 (±0.2). This value is less than the one expected from the association of freely moving molecules, indicating that the hydrophobic interactions of the 1-propanol aliphatic chains decrease the strength of the hydrogen bond between water and alcohol in the hydrate.Key words: IR spectroscopy, ATR spectroscopy, 1-propanol, liquid, aqueous solutions, eigenspectra, hydrate, factor analysis.

New Insights into Pervaporation Mass Transport under Increasing Downstream Pressure Conditions: Critical Role of Inert Gas Entrance

The influence of the total downstream pressure on the pervaporation flux of a pure compound through a dense polymer membrane has been the subject to controversial debates recently. Experimental arguments in favor of either the solution−diffusion model or the newly proposed pore-flow model are alternatively reported on different systems. To critically reexamine this debate, an experimental study under controlled downstream conditions has been performed for pure methanol and pure 2-propanol pervaporation through a poly(dimethylsiloxane) film, the latter having been previously reported to follow pore-flow model predictions. It is shown that a rational analysis of the effects of the downstream pressure on the results can be achieved according to the classical solution−diffusion model, provided that the influence of air leaks in the installation is properly taken into account. Based on this observation, the implications of an inert gas contribution, generally speaking, on pervaporation operation are discussed.

Article

As a foundation for a future measurement of solvated electron mobilities in alcohol-water mixed solvents, the electrical conductances of sodium tetraphenylboride (STPB) in methanol-water, ethanol-water, and 2-propanol-water were measured at different temperatures. The molar conductivity LAMBDA 0 (10-4 S m2 mol-1) of STPB at 298 K is 70 in pure water and 82 in pure methanol; in methanol-water mixed solvents it passes through a minimum, the value being 45 at 70 mol% water. In 2-propanol-water LAMBDA 0 (10-4 S m2 mol-1) at 298 K decreases rapidly from 70 in pure water to 22.6 in 80 mol% water, then gradually to 16.5 in pure 2-propanol. Behavior in ethanol-water is intermediate, with a minimum of 29.5 in 70 mol% water, gradually increasing to 35.5 in pure ethanol. The product of LAMBDA 0 and the solvent viscosity eta has a maximum at about 75 mol% water in methanol, 90 mol% water in ethanol, and 95 mol% water in 2-propanol. The effects are attributed to changes of solvent structure and of solvated ion radius as alcohol is added to water.Key words: alcohol-water mixed solvents, electrical conductivity, large ions, solvent effects, activation energy.

An FT-EPR Investigation of the Anomalous CIDEP Observed in Photoinduced Reactions of Xanthone with Alcohols in the Presence of Hydrochloric Acid

CIDEP spectra from free radicals produced by the photolysis of xanthone (Xn) in 2-propanol were investigated with FT-EPR. The spectra were assigned to the 2-hydroxypropan-2-yl (2HP) and xanthone ketyl (XnH) radicals. In pure 2-propanol and 2-propanol containing 10% H2O, the spectra display low field emission/high field absorption with net emission (E*/A) type polarization. The observed CIDEP pattern is mainly due to the S−T0 radical pair mechanism (RPM) with minor contributions from the triplet mechanism (TM) and radical triplet pair mechanism (RTPM). Upon addition of HCl, the polarization changes to net absorption. The rise time of the absorptive signals is determined by the response time of the spectrometer (∼3 × 10-8 s). Transient optical absorption measurements show that the triplet state of xanthone (3Xn*) is quenched by HCl, and the change in spin polarization produced by HCl addition is attributed to this quenching process. The dependence of the CIDEP pattern and triplet xanthone lifetime on HCl co...

Fate of a Highly Strained Hydrocarbon in Aqueous Soil Environment

Quadricyclane, a highly strained hydrocarbon, is currently being evaluated by the U.S. Air Force as a possible high-performance aviation fuel. It is therefore important to discover how it would interact with the environment in the event of a spill. The reactions of quadricyclane were investigated in water, 50/50 wt % water/2-propanol and pure 2-propanol, and in abiotic aqueous soil environments consisting of four different naturally occurring soils. The reaction products were exo-5-norbornen-2-ol and nortricyclyl alcohol. The reactions in the three solvent systems were pseudo-first-order in quadricyclane. Second-order rate constants were determined from plots of the pseudo-first-order rate constants versus [H+] and were found to be 26.0 L mol-1 min-1 in water, 0.195 L mol-1min-1 in 50/50 water/2-propanol, and 0.099 L mol-1min-1 in 2-propanol, all at 25 °C. The soil experiments were run for periods of up to 9 months. The most important factor affecting the reactivity of quadricyclane in the soils was pH, w...

Comparison of the Photoelectronic and Photocatalytic Activities of Various Anatase and Rutile Forms of Titania in Pure Liquid Organic Phases and in Aqueous Solutions

Various titania samples of industrial origin (Degussa and Tioxide) have been characterized by electrical photoconductance measurements and tested as photocatalysts in various liquid media (either pure organic liquids or aqueous solutions) as a function of their structure (anatase versus rutile). Anatase was constantly found more active than rutile, whatever the reaction chosen (mild oxidation of pure cyclohexane and 2-propanol; total degradation of phenol and nitrophenol isomers in water). In identical conditions, Degussa was found more active, but the intrinsic activity, expressed in moles converted per hour and per square meter of active surface, was found slightly higher for anatase Tioxide. The higher activity of anatase with respect to that of rutile could be explained by the interpretation of the photoconductance measurements, which evidence the higher aptitude of anatase (i) to photoadsorb oxygen, in O2- and O- forms; (ii) to photodesorb it; and (iii) to have a lower relative electron−hole recombin...

Imaging soft samples with the atomic force microscope: gelatin in water and propanol

We have imaged mica coated with thin gelatin films in water, propanol, and mixtures of these two liquids by atomic force microscopy (AFM). The elastic modulus (Young's modulus) can be tuned from 20 kPa to more than 0.1 GPa depending on the ratio of propanol to water. The resolution is best in pure propanol, on the order of 20 nm, and becomes worse for the softer samples. The degradation in resolution can be understood by considering the elastic indentation of the gelatin caused by the AFM tip. This indentation becomes larger and thus the contact area becomes larger the softer the sample is. Therefore this study may be used to estimate the resolution to be expected with an AFM on other soft samples, such as cells. Nondestructive imaging was possible only by imaging at forces < 1 nN. This was difficult to achieve in contact mode because of drift in the zero load deflection of the cantilever, supposedly caused by temperature drift, but straightforward in tapping mode.

Effects of mixed alkanols as cosurfactants on single phase microemulsion properties

The phase behaviour and properties of a microemulsion system cyclohexane-SDS+alkanolwater, where alkanol indicates various mixtures of two short chain alcohols, were studied. The alcohols used as cosurfactants were propanol and hexanol. The surfactant to cosurfactant weight ratio was kept at 1:2. The phase behaviour study includes determination of the phase diagram and Winsor transitions while the properties studied were conductance, viscosity and adiabatic compressibility. The area of the single phase microemulsion region in the ternary phase diagram increased considerably in systems containing mixed alkanols as cosurfactants, compared with pure alkanol containing systems. The nature of Winsor transitions also changed drastically when an alkanol mixture was used. Temperature increase induces a Winsor transition in the order II→III→I in the mixed systems which was opposite to the trend observed in the pure propanol containing system. The conductivity studies in the mixed alkanol systems revealed that the mixtures of two alkanols behave somewhat like alcohols of carbon chain lengths (C 4 or C 5) intermediate between those of the two components. The viscosity and adiabatic compressibility studies highlighted the nonideal behaviour of mixing.

Vapor-Liquid Equilibria and Salt Apparent Molar Volumes of the Water + 2-Propanol + Tetrabutylammonium Bromide System

Vapor-liquid equilibrium and density measurements have been performed on 1.00-5.89 m tetrabutylammonium bromide (TBAB) in mixtures of 2-propanoland water. The VLE experiments were performed using a modified Othmer still at ambient pressure. The effect of salt on the relative volatility of 2-propanol was evaluated at molalities of 1.00,1.79, and 5.89 over the full range of solvent composition. At each salt molality, as the alcohol concentration increased, salting-in and then salting-out behavior of the alcohol was observed. The azeotrope was shifted but apparently not eliminated for the salt concentrations studied. Density measurements at 25,40, and 55 C were taken using a vibrating tube densimeter at four salt molalities over the full range of solvent composition. As salt molality increases, the apparent molar volume of TBAB exhibits a minimum between 1 to 2 m TBAB in pure water, it is slightly larger and monotonically increases in pure 2-propanol, and it is larger yet, with a maximum at lower 2-propanol amounts, in the ternary mixture.