Water ethanol solutions

Water at 20°C rests on solid naphthalene with a contact angle of 90°, while a water-ethanol solution of surface tension 3S dyn/cm shows an angle of 30°. Calculate (a) the work of adhesion of water to naphthalene, (b) the criticd surface tension of naphthalene, and (c) y for naphthalene. 

Many hydantoins are endowed with significant pharmacological activities as highlighted by 5,5-diphenylhydantoin (Dilantin ), an anticonvulsant and antiepileptic discovered by Parke-Davis in 1940 s. Despite the lapse of more than half a century, Dilantin still plays an important rote in modem medicine. Meanwhile, another anticonvulsant 15 was synthesized from 9,10-dimethoxy-l,3,4,6,7,llb-hexahydro-pyrido[2,l-a]isoquinolin-2-one (14) under the standard Bucherer-Lieb variation in a 2 1 water-ethanol solution (15a 15b = 8 l). ... 

Maldotti (96) studied the kinetics of the formation of the pyrazine-bridged Fe(II) porphyrin shish-kebab polymer by means of flash kinetic experiments. Upon irradiation of a deaerated alkaline water/ethanol solution of Fe(III) protoporphyrin IX and pyrazine with a short intense flash of light, the 2 1 Fe(II) porphyrin (pyrazine)2 complex is formed, but it immediately polymerizes with second-order kinetics. This can be monitored in the UV-Vis absorption spectrum, with the disappearance of a band at 550 nm together with the emergence of a new band due to the polymer at 800 nm. The process is accelerated by the addition of LiCl, which augments hydrophobic interactions, and is diminished by the presence of a surfactant. A shish-kebab polymer is also formed upon photoreduction of Fe(III) porphyrins in presence of piperazine or 4,4 -bipyridine ligands (97). 

For the extraction of colourants from Rubia tinctorum (Figure 13.2) roots, mostly methanol, [42] water-methanol (with the addition of n-amyl alcohol in the case of lake extraction)[19,20] or water-ethanol solutions[38] are used. Additional hydrolysis can be performed with hydrochloric acid[8,19,20,34] and trifluoroacetic acid,[42] but also with madder root enzymes,[42] responsible for cleavage of anthraquinone glycosides into the corresponding aglycones and sugars. 

Dissolve a silane coupling agent in the acidic water/ethanol solution with stirring to a final concentration of 2-5 percent (v/v). Allow hydrolysis to occur for 5 minutes at room temperature to form reactive silanols. 

Put a chemical beaker with a water-ethanol solution of sulphur onto shelf 4. Switch on the lamp. Shut the door of the box and through an opening in it observe the luminous cone in the colloidal solution. Re-... 

Comparison of Aqueous and Water-Ethanol Solutions. The effect of the presence of ethanol in aqueous solutions of sodium hydroxide is usually small. This is shown by the similar shape of the dependence of J- on sodium hydroxide concentration (Figure 1) and by the small differences m J values obtained at the different constant ethanol concentrations up to 90 vol % (Table III). Even when the concentration of sodium hydroxide was kept constant (e.g., 0.1 M), the difference between J values in 90 vol % ethanol and 98 vol % ethanol was only 0.16 J- units (Figure 2). In this range of ethanol concentrations, it is necessary to consider the competitive influence of ethoxide ions, the addition of which would result in a decrease of the C6H5CO— absorbance indistinguishable from the decrease caused by hydroxide ion addition. In 90 vol % ethanol, the ratio of hydroxide and ethoxide concentrations is about 1 1, while in 98 vol % ethanol, it is possible to extrapolate (30) that about 90% of the base will be present as the ethoxide ion. 

Dithiocarbamato (dtc) complexes are prepared by mixing VOS04 and the ligand ii water-ethanol solutions. Some of the isolated complexes are in Table 34 they are susceptibh to air oxidation, especially in solution, and are generally monomeric. 

M. Yoshikawa, T. Yukoshi, K. Sanui, N. Ogata, Selective separation of water from water-ethanol solution through quarternized poly(4-vinyl pyridine-co-acrylonitrile) membranes by pervaporation technique, J. Appl. Polym. Sci. 33 (1987) 2369-2392. 

Extensive properties of multicomponent phases (solutions) are related to the amount of material in the phase, but may not be just the sum of the properties of the constituent components. Probably the best known example of this difference is the observation that mixing 1.0 L of ethanol with 1.0 L of water at standard temperature and pressure (STP) produces 1.93 L of water-ethanol solution. We define the difference between an extensive property of the solution and the sum of the properties of its pure components as the property change of mixing for the solution ... 

We have studied photocatalytic properties of nanostructured metal-semiconductor composites, made from mesoporous samples of Ti02 and a number of metals (Cu2+, Ni2+, Co2+, Cd2+, Fe2+, Ag+, Zn2+, Pb2+) in hydrogen evolution from water-ethanol solutions. Correlations between the quantum yields of the photoreaction and various parameters of the reacting system (such as the metal nature and concentration, photocatalyst quantity, light intensity, temperature) have been found and discussed. It has been shown, that maximal quantum yield of hydrogen production (y = 0.44) could be achieved in case of Ti02/Cu composite. 

Bamwenda, G.R., S. Tsubota, T. Nakamura and M. Haruta (1995). Photoassisted hydrogen-production from a water-ethanol solution - a comparison of activities of Au-Ti02 and Pt-Ti02. Journal of Photochemistry and Photobiology A-Chemistry, 89(2), 177-189. 

In the particular case of the carboxylates of the eosin family, a careful examination of electron transfer paths was made by K. Tokumaru and cowor-kers [158, 159, 160]. They found that eosin Y (EY ) was able to sensitize hydrogen evolution from water under visible light irradiation in a system made of an amine donor, methyl viologen (MV2+) mediator and redox catalyst such as colloidal platinum. In a water-ethanol solution of EY, in the presence of MV2+ and triethanolamine (TEOA), a maximum quantum yield of 0.3 was measured for the MV + radical cation formation. Kinetic measurements of the EY triplet quenching constant by MV2+ (kq = 3.109 M 1 s 1) and TEOA... 

Fig. 3.96. DSC-thermograms of water-ethanol solution of DMPC, containing 2 mg ml 1 DMPC and 7-10 2...

Given the following data for water — ethanol solutions at 250°C, calculate and 7c2h5oh relative to the solvent standard states for each component at xH 0 - 0.1, 0.2,... 

Water/ethanol solution Model white wine Model red wine F Model red wine 2 Red wine... 

Berman et al. (1968) noted that mannitol is unusual among carbohydrates in that exists in several polymorphic forms , indicating that a number of these are often obtained simultaneously. They describe the preparation of a number of these modifications. The a form is obtained by slow crystallization from 96 per cent ethanol, the a form by evaporation from 100 per cent ethanol and the p form from aqueous ethanolic solutions, all apparently under thermodynamic conditions. On the other hand the y form is obtained kinetically by rapid cooling of a 1 1 water-ethanol solution. An additional k form was obtained (unexpectedly) upon evaporation of a boric acid/methanol solution (Kim et al. 1968). 

I. Weinberg and J. R. Zimmerman. J. Chem. Phys. 23, 748-9 (1955). NMR concentration dependence of chemical shifts in water-ethanol solutions. 

When water is mixed with another liquid, the number of bonds can increase, as, for instance, in water-ethanol solutions (structure formers) or decrease (structure breakers). However, in all cases, the tetrahedral structure vanishes (except, of course, for isotopic mixtures of light and heavy water). As a consequence, the anomalies of liquid water are strongly reduced upon addition of other components. For instance, 7% of ethanol is sufficient to completely suppress the maximum in the temperature dependence of the density of the mixture [9]. 

Pipeline Mixers used as Reactors for Fast C/C Reactions. Taylor (1996) and colleagues (1998) conducted a study to determine scale-up procedures for fast C/C reactions in pipeline mixers. They used the fourth Bourne reaction, which is the acid catalyzed hydrolysis of dimethoxypropane (DMP) to acetone and methanol. This is an extremely rapid reaction when catalyzed by HCl. The competitive reaction scheme, which is a unique one, is one in which NaOH reacts practically instantaneously with the HCl to remove the catalyst for the hydrolysis reaction. A water/ethanol solution of NaOH and DMP was fed as a main stream to a Kenics helical element mixer and an aqueous side stream containing slightly greater (abour 5% greater) than equimolar amount of NaOH was fed as the side stream. The product was analyzed by GC for methanol and acetone. For extremely rapid mixing, essentially no hydrolysis occurred however, for slow mixing, essentially all the DMP is hydrolyzed because acidic conditions cause very rapid hydrolysis of the DMP. 

The diaqua(2,6-diacetaylpyridinedisemicarbazone)indmm(III) cation (72) represents the first example featuring a pentagonal bipyramidal indium site." It was isolated as [In(H2DAPSC)(H20)2](N03)2(0H) by reacting hydrated indium nitrate and 2,6-diacetylpyridine bis(semicarbazone) (H2DAPSC) in a water-ethanol solution. 

Synthesis of Model Compounds. We have synthesized semi-rigid rod LC polyesters based on poly(methylphenylene bromoterephthalate-co-hexamethylene bromoterephthalate) (Fig. 1) by random copolymerization. The details of the synthesis of these polymers have been reported previously (fi), and are shown schematically in Fig. 1. All chemicals were purchased from Aldrich methyl hydroquinone, and 1,6-hexanediol were used as received. Bromoterephthalic arid (96%) was recrystallized with an 80/20 vol-% distilled water/ethanol solution. Pyridine (used a proton acceptor) was distilled and stored with desiccant. Solvents were used as received, and all glassware was oven dried. 

The C-3 adduct 37, presumed earlier to be the structure of the product obtained on refluxing 3-chloro-5,6-diphenyl-l,2,4-triazine in a water-ethanolic solution, was not detected the product was found later to be 5,6,-diphenyl-l,2,4-triazin-3-one (Scheme 25) (82CPB152). 

Fig. 5a shows the adsorption isotherm of cymarin from water - ethanol solution determined under static conditions. One can see from this figure that this isotherm is convex towards the n axis although the equilibrium concentrations are rather low. Extrapolating the derivative of adsorption by concentration towards zero concentrations, the Henry con-... 

The data of Table 1-4 make it possible to understand the mechanism of adsorption of steroid compounds on hydrophobic surface of adsorbents from water- ethanol solutions and the role in adsorption of different functional groups of these substances. 

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