Aqueous Alcohol Systems Research Articles

Effect of solvent type on the formation rate of benzyl cation intermediate in acidolysis of lignin

Abstract The purpose of this study was to examine how the type of solvent among aqueous 1,4-dioxane, tetrahydrofuran, ethanol, iso-propyl alcohol, or ethylene glycol and its content (mol%) affect the formation rate of benzyl cation intermediate (BC) in the acidolysis of lignin, using a simple model compound, 1,2-dimethoxy-4-methoxymethylbenzene. Because the BC forms from the model compound via two steps, i.e., protonation of the benzyl methoxymethyl group as the pre-equilibrium step and liberation of the methanol as the rate-determining step, the observed variation of the formation rate with type of solvent and solvent content originates from the effects on both steps undistinguishably. The formation rate of BC decreased with increasing mol% of any of the organic solvents for a range of relatively low mol%, but increased with it for relatively high mol%. The formation rate varied more in the ether than in the alcohol systems. These results seem to be regulated by the effect of changing the mol% on the pre-equilibrium step, i.e., on the proton activity, rather than on the rate-determining step. Two reaction products, 4-alkoxymethyl-1,2-dimethoxybenzene and 4-hydroxymethyl-1,2-dimethoxybenzene, exclusively formed in the aqueous alcohol systems. The former compound was confirmed to be thermodynamically more stable and kinetically the more favorable product.

Optical studies of acefylline piperazine, chlorpheniramine maleate, thiamine hydrochloride in aqueous, aqueous methanol and aqueous ethylene glycol systems

Refractive index, FTIR and Uv–vis absorption study of acefylline piperazine, chlorpheniramine maleate, thiamine hydrochloride was done to investigate the solute-solvent interactions. The interaction of drugs (AP, CPM, TAD) studied in aqueous, aqueous methanol and aqueous ethylene glycol systems at 303 K. Specific refraction, Molar refraction and polarizability of drugs in aqueous and aqueous alcoholic systems was calculated by using Lorentz-Lorentz equation. FTIR study of drugs in aqueous and aqueous alcoholic systems was undertaken to analyze the compatibility of drugs in studied systems. The UV–vis absorption study has also been done to interpret the interaction patterns occurring in drugs and solvent systems.

Hafnia–Silica Cryogels: Solvent‐Assisted Textural and Catalytic Control in the Citronellal Cyclization

AbstractA series of hafnia–silica mixed oxides of HfO2(SiO2)8 stoichiometry were prepared by a sol–gel method followed by freeze‐drying. Two hafnium precursors, Hf(OiPr)4 and Hf(OtBu)4 were examined under a variety of aqueous–alcoholic systems. A decisive dependence of the alcoholic solvent on the gel formation and the surface and porosity of the final materials was found, which in turn were key to the enhancement of catalysis. Hence, acid hydrolysis and gelification of Hf(OiPr)4 in tert‐butyl alcohol, followed by lyophilization, yielded a material with the highest mesoporosity and specific surface area. This catalyst behaved most efficiently in the acid‐catalyzed cyclization of citronellal to isopulegol at room temperature. Furthermore, this cryogel also presented combined Lewis acidity and hydrogen bonding that resulted in higher diastereoselectivity for the above reaction. These results highlight the effect of how the textural and, therefore catalytic, properties of the cryogels depend decisively on the solvents chosen for their synthesis.

Studies of Partial Molar Volumes of Some Narcotic-Analgesic Drugs in Aqueous-Alcoholic Mixtures at 25°C

Partial molar volumes of the drugs Parvon Spas, Parvon Forte, Tramacip, and Parvodex in aqueous mixtures of methanol (MeOH), ethanol (EtOH), and propan-1-ol (1-PrOH) have been determined. The data have been evaluated using the Masson equation. The parameters, apparent molar volumes \({(\phi_{\rm v})}\), partial molar volumes \({(\phi_{\rm v}^{0})}\), and Sv values (experimental slopes) have been interpreted in terms of solute–solvent interactions. In addition, these studies have also been extended to determine the effect of these drugs on the solvation behavior of an electrolyte (sodium chloride), a surfactant (sodium dodecyl sulfate), and a non-electrolyte (sucrose). It can be inferred from these studies that all drug cations can be regarded as structure makers/promoters due to hydrophobic hydration. Furthermore, the results are correlated to understand the solution behavior of drugs in aqueous-alcoholic systems, as a function of the nature of the alcohol and solutes.

Grape cane waste as a source of trans-resveratrol and trans-viniferin: High-value phytochemicals with medicinal and anti-phytopathogenic applications

Grape cane waste was investigated as a potential source of high-value phytochemicals with medicinal and anti-phytopathogenic applications. Extraction yields of trans-resveratrol and trans-ɛ-viniferin from Vitis vinifera cv. Pinot Noir grape cane were 3.45 ± 0.04 and 1.30 ± 0.07 mg g −1 dw, respectively. The analyte extraction efficiencies were investigated using protic and aprotic solvents. Yields varied 22-fold over the range of solvent systems investigated, demonstrating the importance in solvent polarity and hydrogen bonding capability for efficient extractions. The current study suggests that these compounds can be quantitatively extracted from grape cane residue using low-cost, environmentally benign, and non-toxic aqueous alcoholic solvent systems such as ethanol:water mixtures. With current commercial values of trans-resveratrol and trans-ɛ-viniferin between US$ 2000 and US$ 3000 per kg, established stilbene yields from cane waste could represent an agricultural coproduct valued at US$ 2000–US$ 3000 per hectare of production. At present levels of worldwide wine grape production, the extraction of trans-resveratrol and trans-ɛ-viniferin from grape cane waste may reach a global economic value of >$30 billion.

High-Value Phytochemicals from Grape Cane Waste: Potential Value-Added Viticultural Sources of Trans-Resveratrol and Trans-e-Viniferin with Medicinal and Anti-Phytopathogenic Applications

AbstractGrape canes as agricultural waste from commercial viticultural activities represent a potentially important source of the well-known medicinal and anti-phytopathogenic stilbene compounds trans-resveratrol and trans-e-viniferin. Reports in the literature suggest that concentrations of these compounds range up to 5 mg/g dw and 2 mg/g dw, respectively, and can be quantitatively extracted from the cane residue using low-cost, environmental benign, and non-toxic aqueous alcoholic solvent systems such as ethanol:water mixtures. With current commercial values of these compounds between US$2,000 to US$3,000 per kg, established stilbene yields from cane waste could represent an agricultural coproduct valued at US$2,000 to US$3,000 per hectare of production. At the present worldwide wine grape production of 8,000,000 ha, the extraction of trans-resveratrol and trans-e-viniferin from grape cane waste would have an estimated global economic value of >$30 billion.

Viscosity studies of some narcotic–analgesic drugs in aqueous–alcoholic mixtures at 25 °C

Viscosities of drugs namely Parvon Spas, Parvon Forte, Tramacip and Parvodex in various aqueous mixtures of alcohols (methanol, ethanol and 1-propanol) have been determined. These studies are further extended for solutes like the electrolyte sodium chloride, the surfactant: sodium dodecyl sulphate and the non-electrolyte sucrose in the presence of these drugs. The viscosity data have been analyzed for the evaluation of A and B viscosity coefficients using Jones–Dole equation. A-coefficients are found to be negligible implying weak ion–ion interactions whereas B-coefficients are found to be positive thereby showing drug–solvent interactions. It can be inferred from these studies that all the drug cations can be regarded as structure-makers/promoters due to hydrophobic hydration of the drug molecules. Furthermore, the results are correlated to understand the solution behavior of drugs in aqueous alcoholic systems as a function of the nature of alcohols and different types of solutes.

Application of a New Method to Reproduce the Enthalpies of Transfer of NaI from Water to Aqueous Methanol, Ethanol and iPrOH Solvent Systems at 298 K

The enthalpies of transfer, , of NaI from water to aqueous methanol, ethanol and isopropanol, iPrOH, systems are reported. These data have been analysed in terms of the new solvation theory. These data are considered in terms of the new developed solvation theory including variable (n + N), the net effect of the solute on the solvent-solvent bonding, is positive if there is a net breaking or weakening of solvent-solvent bonds. The solvation parameters recovered from the analyses indicate that the net affect of NaI on solvent structure is a breaking of solvent-solvent bonds and that NaI is preferentially solvated by water in all aqueous alcohol systems considered. (n + N) values increase with increasing in the size of the alcohol alkyl residue from methanol to iPrOH.䢑�⨀਀䢑�⨀墑�⨀؀က墑�⨀?塢Ѐက肑�⨀肑�⨀

Speed of sound measurements conducted at high pressures on aqueous alcohol and aqueous diol systems at T= 298.15 K

The pulse echo overlap technique has been used in conjunction with three unique high-pressure cells to measure ultrasonic speeds of sound in dilute aqueous solutions of the alcohols 2-propanol, 2-butanol, 2-propanol and 2-hexanol and the diols 1,4-butanediol, 1-5-pentanediol and 1,6-hexanediol at p = 0.1, 20.0, 40.0, 60.0, 80.0 and 120.0 MPa and T = 298.15 K. A procedure is described by which the sound velocity measurements may be utilised to calculate precise densities and apparent molar volumes. The concentration and pressure dependences of the calculated apparent molar volumes have been modelled using empirical equations which in turn have been used to obtain values for apparent molar volumes at infinite dilution. In addition, measured speeds of sound have been used to calculate isentropic and isothermal compressibilities, and their associated apparent molar properties, for the investigated aqueous alcohol and diol systems. The latter properties have also been modelled as functions of concentration and pressure using empirical equations to obtain the pressure dependences of the apparent molar properties at infinite dilution. A group additivity approach has been used to model the pressure dependences of apparent molar volumes at infinite dilution. This analysis has provided estimates of the pressure dependences of the contributions of methylene and hydroxyl groups to apparent molar volumes at infinite dilution.

10-Methylacridinium ion as a fluorimetric probe measuring the activity of halide anions in aqueous solutions of cationic surfactants

The quenching of fluorescence of 10-methylacridinium ion by inorganic anions in aerated aqueous solutions was studied at room temperature. In the case of cationic surfactants, with chloride and bromide anions as counterions, characteristic breaks on the Stern–Volmer plots could be observed at concentrations corresponding to the critical micelle concentration of the surfactants. It is shown that the ratio of the slopes of the two linear fragments of the plots, in the micellar and premicellar concentration ranges, gives an estimate of the value of the ionization degree, α, of the micelles. This approach is applicable also in aqueous–alcohol systems.

Marked Difference in Solvation Effects and Mechanism between Solvolyses of Substituted Acetylchloride with Alkyl Groups and with Aromatic Rigns in Aqueous Fluorinated Alcohol and in 2,2,2-Trifluoroethanol-Ethanol Solvent Systems

Solvolyses rate constants of trimethylacetyl chloride (2), isobutyryl chloride (3), diphenylacetyl chloride (4) and p-methoxyphenylacetyl chloride (5) in 2,2,2-trifluoroethanol (TFE)-water, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)-water and TFE-et hanol solvent systems at <TEX>$10^{\circ}C$</TEX> are determined by a conductimetric method. Kinetic solvent isotope effects (KSIE) are reported from additional kinetic data for methanolyses of various substituted acetylchlorides in methanol According to the results of those reactions analyzed in terms of rate-rate profiles,extended Grunwald-Winstein type correlations, application of a third order reaction model based a general base catalyzed (GBC) and KSIE values. Regardless of the kind of neighboring groups (CH3- or Ph-groups) of reaction center, for aqueous fluorinated alcohol systems, solvolyses of 2, 3, 4, and 5 were exposed to the reaction with the same mechanism (a loose SN2 type mechanism by electrophilic solvation) controlled by a similarity of solvation of the transition sate (TS). Whereas, for TFE-ethanol solvent systems, the reactivity depended on whether substituted acetyl chloride have aromatic rings (Ph-) or alkyl groups (CH3-); the solvations by the predominant stoichiometric effect (third order reaction mechanism by GBC and/or by push-pull type) for Ph- groups (4 and 5) and the same solvation effects as those shown in TFE-water solvent systems for CH3- groups (2 and 3) were exhibited Such phenomena can be interpreted as having relevance to the inductive effect ( <TEX>$\sigmaI)$</TEX> of substituted groups; the plot of log (KSIE) vs. <TEX>${\sigma}I$</TEX> parameter give an acceptable the linear correlation with r = 0.970 (slope = 0.44 <TEX>$\pm$</TEX> 0.06, n = 5).

Henry's Law Constants of Chlorinated Ethylenes in Aqueous Alcohol Solutions: Measurement, Estimation, and Thermodynamic Analysis

Henry's law constants of tetrachloroethylene, trichloroethylene, cis-dichloroethylene, and trans-dichloroethylene in air−aqueous alcohol systems were measured. Ethanol, 1-propanol, and 2-propanol were employed as cosolvents. Alcohol concentrations ranged from 0 to 20 vol %. Measurements were taken at temperatures from 0.2 to 70.0 °C. Using the experimental results, equations for the estimation of Henry's law constant as a function of both temperature and alcohol concentration were constructed. In addition, the Gibbs free energy (ΔdisG), enthalpy (ΔdisH), entropy (ΔdisS), and heat capacity change (ΔdisCp) associated with dissolution (solution to gas transfer) were derived by employing a linear regression analysis of the temperature dependence of the Henry's law constant.

Sorption and permeation of binary water-alcohol systems through PVA membranes crosslinked with multifunctional crosslinking agents

Sorption and permeation of aqueous alcohol (C1–C4) through PVA membrane cross-linked with a multifunctional cross-linker is reported. The effect of temperature, feed concentration, cross-linker loading and the shape and size of the permeating species on pervaporation characteristics is investigated. Sorption isotherms of cross-linked PVA are obtained for the aqueous alcohol systems namely water+methanol, +ethanol, +n-propanol, +isopropanol, +n-butanol and +isobutanol. Values of activation energy for permeation (ΔEp), diffusion (ΔEd) and heat of sorption (ΔHs) for water through cross-linked PVA are estimated. The value of ΔEd for water was found to vary for all the water-alcohol systems (20–50 kJ mole-1) covered in this work.

The hydrolysis of azidoprofen esters: A model for a soft anti-inflammatory drug for topical application

A series of ester prodrugs of azidoprofen was investigated for susceptibility towards in vitro enzymatic and chemical hydrolysis. In each case, the parent acid was regenerated with the rate and extent of the process being dependent on the nature of the ester moiety. All esters, with the exception of the glycolamide derivative, exhibited much greater lability towards enzyme-mediated hydrolysis compared to chemical decomposition. In particular, the tetrahydropyranylmethyl ester showed the largest difference in sensitivity towards these two processes. This specificity is an important requirement in prodrug design and indicates the capacity to undergo rapid metabolic activation while exhibiting stability under conditions encountered during formulation and storage. The ability of skin to activate these prodrugs was demonstrated by hydrolysis of the methyl ester of azidoprofen on incubation with a hairless mouse skin homogenate. In addition, when enzymatic hydrolysis was monitored in aqueous alcoholic systems competitive hydrolysis and enzyme-mediated transesterification were observed. The rate of both processes increased with a longer chain ester and transesterification was the predominant reaction. Eventually, the new ester also underwent enzyme-mediated hydrolysis to yield azidoprofen.

Enthalpies of transfer of 2-methyl-2-propanol from water to mixtures of water with methanol, ethanol and 1,4-dioxane

The enthalpies of transfer of 2-methyl-2-propanol (TBA) from water to mixtures of water with methanol, ethanol and 1,4-dioxane have been measured. The data are considered in terms of recently developed theory, and it is found that the enthalpies of transfer can be reproduced quantitatively over most of the composition range in each solvent system. The parameters recovered from the analyses indicate that the net effect of TBA on the solvent structure is a breaking of solvent-solvent bonds and that TBA is preferentially hydrated in the aqueous alcohol systems, but randomly solvated in the water+1,4-dioxane system. It is also found that the model parameters for TBA solvation in the alcohol systems are independent of the alcohol.

A microscopical study of the pathway for diffusion of rhodamine B and octadecylrhodamine B into wool fibres*

The pathways for the diffusion of the basic dyes rhodamine B and octadecylrhodamine B into wool under aqueous and non–aqueous dyeing conditions have been investigated. The distribution of each dye within the fibre at various stages of the dyeing process was monitored by fluorescence microscopy. By judicious choice of solvent system and treatment time, the dyes could be directed into different histological components of the fibre. Intercellular diffusion, involving passage of the dye through the cell membrane complex between the cortical cells, was generally the preferred route for penetration of the fibre. The distribution patterns of the two dyes differed markedly and were strongly dependent upon the solvent composition. Whilst selective staining of the cell membrane complex occurred in an anhydrous solvent system, preferential staining of that region of the cell membrane complex associated with the orthocortex resulted when the dyes were applied from aqueous alcohol systems.

The radiation chemistry of rhodium complexes in aqueous alcoholic systems

Radiation decomposition of rhodium complexes Rh 2(C 6H 5OOCCHOH) 4, Rh 2(OOCH) 4, Rh 2(OOCCH 3) 4, Rh(acac) 3 and Rh(acac)(CO) 2 has been examined in aqueous systems both in liquid and frozen glassy states. Steady state γ-radiolysis and pulse radiolysis have been applied. The yields of radiation decomposition of the complexes as well as the rate constants of electron scavenging have been determined. The mechanism of radiation decomposition of the examined compounds has been discussed.

The evidence and applications of equilibria between hydroxide and alkoxide ions in aqueous-alcoholic systems

The composition of solvolysis products of butyl bromide, acetanhydride, and benzoyl chloride has been followed aqueous alcohol in alkaline and (except for butyl bromide) also in neutral regions. The results have been used as a piece of evidence of the existence of equilibrium between hydroxide and alkoxide ions and for evaluation of the possibility of calculation of the concentration ratio of hydroxide and alkoxide ions from the concentration ratios of the products as well as for evaluation of selectivities of the solvolytic reactions for mechanistic purposes.

Potentials of average force for an interaction site model of aqueous alcohols: a molecular model for the hydrophobic bond

An interaction site model with simple square-well potentials of average force is shown, to accurately fit experimental second osmotic virial coefficients for a number of aqueous alcohol systems. The model takes into account the nonspherical structure of the alcohol molecules, includes all important orientational effects, and considers all interactions of the sites

High-resolution carbon-13 nuclear magnetic resonance studies of maize proteins

The first high-field, high-resolution 13 C nuclear magnetic resonance spectra of zein, and two sub-fractions obtained by extraction in aqueous alcohol systems, are reported. Solubility of zein was also investigated in fourteen different organic solvents and found to be optimal in 100% DMSO and 50% pyridine-water. The effects of extraction or pretreatment of zein with specific solvents were also investigated. Spectral assignments are proposed for zein based on a comparison of the 13 C chemical shift values for peaks in the zein spectra with previously published 13 C chemical shift assignments for proteins. Biochemical characterization of the protein samples by SDS-PAGE and amino acid analysis were carried out in parallel with the NMR studies to aid in the interpretation of NMR spectra.