Water-alcohol mixtures, acidity constant

The crudeness of the modeP should dissuade us from accepting this as gospel. Current disillusionment with the Born equation is understandable, but its minor triumphs should not be denied. It does predict that Ap for molecular acids should be a linear function of the reciprocal of the dielectric constant, and this is verified for water-alcohol mixtures of moderate to high dielectric constant. ... 

The reactions studied included oxidation (using hydrogen peroxide) and reduction (using thioglycolic acid) of keratin cystine. Traditionally, reactions of keratin are performed in water-alcohol mixtures. These reactions were carried out along two lines in the pseudoternary phase diagram, one representing constant (35%) surfactant concentration and the other constant (15%)... 

Methyl ethyl ketone. Use the apparatus of Fig. Ill, 61, 1 but with a 500 ml. round-bottomed flask. Place 40 g. (50 ml.) of see. butyl alcohol, 100 ml. of water and a few fragments of porous porcelain in the flask. Dissolve 100 g. of sodium dichromate dihydrate in 125 ml. of water in a beaker and add very slowly and with constant sturing 80 ml. of concentrated sulphuric acid allow to cool, and transfer the resulting solution to the dropping funnel. Heat the flask on a wire gauze or in an air bath until the alcohol mixture commences to boil. Remove the flame and run in the dichromate solution slowly and at such a rate that the temperature... 

Ethyl nitrite may be prepared by dissolving 38 g (0.55 mol) of sodium nitrite in 120 ml of water in a 500-ml flask equipped as above. Dilute 23 g (29 ml, 0.5 mol) of ethanol with an equal volume of water, carefully add 25 g (13.5 ml) of concentrated sulphuric acid and dilute to 120 ml with water. Cool both solutions to —10 °C in an ice-salt bath and add the acid-alcohol mixture to the nitrite solution slowly with constant stirring during about 30 minutes. Transfer the reaction mixture to a cooled separating funnel, run off- the lower aqueous phase, wash the ethyl nitrite layer rapidly with ice-cold 2 per cent sodium hydrogen carbonate solution and dry over anhydrous sodium sulphate. The product may be kept at 0°C as a 50 per cent solution in absolute ethanol if required but should be used as soon as possible. The b.p. of pure ethyl nitrite is 17 °C. 

Rates and product selectivities 5 = ([ester product]/[acid product]) x ([water]/ [alcohol solvent] were reported for solvolyses of chloroacetyl chloride at —10 °C and phenylacetyl chloride at 0 °C in EtOH- and MeOH-water mixtures. Additional kinetic data were reported for solvolyses in acetone-water, 2,2,2-trifluoroethanol (TFE)-water, and TFE-EtOH mixtures. Selectivities and solvent effects for chloroacetyl chloride, including the kinetic solvent isotope effect (KSIE) of 2.18 for MeOH, were similar to those for solvolyses of p-nilrobcnzoyl chloride rate constants in acetone-water were consistent with a third-order mechanism, and rates and products in EtOH-and MeOH-water mixtures could be explained quantitatively by competing third-order mechanisms in which one molecule of solvent (alcohol or water) acts as a nucleophile and another acts as a general base (an addition-elimination reaction channel) (29 R = Et, Me, H).23... 

The first mention of the a(x) dependence was in experimental work [265], The dielectric relaxation data of water in mixtures of seven water-soluble polymers was presented there. It was found that in all these solutions, relaxation of water obeys the CC law, while the bulk water exhibits the well-known Debye-like pattern [270,271], Another observation was that a is dependent not only on the concentration of solute but also on the hydrophilic (or hydrophobic) properties of the polymer. The seven polymers were poly(vinylpyrrolidone) (PVP weight average molecular weight (MW) = 10,000), poly (ethylene glycol) (PEG MW = 8000), poly(ethylene imine) (PEI MW = 500,000), poly(acrylic acid) (PAA MW = 5000), poly(vinyl methyl ether) (PVME MW = 90,000), poly(allylamine) (PA1A MW = 10,000), and poly(vinyl alcohol) (PVA MW = 77,000). These polymers were mixed with different ratios (up to 50% of polymer in solution) to water and measured at a constant room temperature (25°C) [265]. 

D) Preparation of Methyl Orange. Add 2.6 g (0.015 moles) of sulfanilic acid to 20 ml of water, and then add 3 ml of 6 A sodium hydroxide solution. Warm slightly until solution is complete. Add 1 g of sodium nitrite, stir until the salt is dissolved, and cool to 25°. Pour this mixture, with constant stirring, into a beaker which contains 30 ml of water, 40 g of crushed ice, and 2 ml of concentrated sulfuric acid. Allow to stand for half an hour, adding ice if the temperature rises above 5°. Add a solution of 2 ml of dimethyl-aniline in 2 ml of hydrochloric acid. Stir, allow to stand for 15 minutes, and add 12 ml of 6 A sodium hydroxide and 50 ml of saturated salt solution. Cool for 10 minutes. Filter by suction, and wash the crystals with 10 ml of cold saturated salt solution. Press the crystals on the filter into a cake to drain well. To recrystallize, suspend the cake in 100-125 ml of distilled water and heat until solution is complete at 90-95°, adding more water if necessary. Filter the hot solution, and cool. Filter the crystals with suction, wash with alcohol and finally with ether. The yield is 3.5-4.0 g. 

One-third of the cold nitric-sulfuric mixture is placed in each of three 500-cc. Erlenmeyer flasks (Note 3), and each portion is treated separately with one-third of the methyl alcohol-sulfuric acid mixture, with constant shaking and thorough mixing (Note 4). The temperature is allowed to rise fairly rapidly to 40° and kept at this point by external cooling. During the addition of the methyl alcohol-sulfuric acid, most of the ester separates as an almost colorless oily layer above the acid. The time required for completion of the reaction is two to three minutes for each flask. The reaction mixtures are allowed to stand in the cold for an additional fifteen minutes but not longer. The lower layer of spent acid is separated promptly and poured at once into a large volume of cold water (about i 1. for each portion) to avoid decomposition which quickly ensues with copious evolution of nitrous fumes. 

As the result of the fermentation there is obtained a mixture which contains water, alcohol, fusel oil, acids, yeast cells, and other substances. The alcohol, which is present to the extent of from 10 to 13 per cent, is separated by distillation. Very efficient rectifying apparatus is used in distilling the dilute solution of alcohol. After two distillations alcohol containing but 4 per cent of water is obtained. A mixture of alcohol and water which contains 96 per cent of alcohol by weight cannot be separated into its constituents by distillation, as a mixture of this composition has a constant boiling point below that of pure alcohol. Toward the end of the distillation there is obtained what is called fusel oil, which consists of two isomeric amyl alcohols, CsHnOH, together with small quantities of other alcohols. 

Kinetic studies of aquation of [Fe(phen)3] and derivatives in binary aqueous media remain popular. A group additivity approach has been applied to aquation of [Fe(5N02phen)3] in aqueous alcohols (faster reaction) and formic and acetic acids (slower), to investigate its potential for mechanism diagnosis. Rate constants for dissociation of the parent complex increase tenfold on going from water to 100% dimethylformamide. Aquation rate constants and activation parameters have also been reported for the 5-nitro, 5-phenyl, and 4,7-diphenyl derivatives in water-dioxan mixtures. Both papers contain obscure discussions of solvolysis mechanisms in DMF-rich and dioxan-rich media. In the latter media it seems that ion pairs play a key role, as evidenced by activation entropies. The discussion of reactivities in terms of hydrophobicities of the complexes and their respective transition states represents a qualitative initial state-transition state analysis. An explicit analysis of this type has been published for the iron(II) complexes of the... 

Eighty-seven milliliters of concentrated sulfuric acid (1.5 mol H2SO4) is poured into 60 ml. of water. The mixture is cooled to 0° in an ice-salt bath and maintained at this temperature while 222 g. (3 mols) of n-butyl alcohol is added slowly, with constant agitation. During the course of an hour this mixture is then introduced beneath the surface of a cold (0°) solution of 228 g. (3.3 mols) of sodium nitrite dissolved in 900 ml. of water, which is contained in a... 

In a mixture of two alcohols, the equivalent of reaction (53) may be regarded as an equilibrium process for which the equilibrium constant is a measure of the relative acidity of the two alcohols. In a water-methanol mixture, for example, the equilibrium reaction is... 

In Lavoisier s work on the analysis of mineral waters eight different mixtures of alcohol and water were used to separate the salts formed on evaporation, a method used by Macquer (see p. 87). The results are of no interest. Lavoisier then believed there were only two mineral acids, sulphuric and hydrochloric the nature of nitric acid is unknown and the idea (Sage s) that phosphoric acid is a peculiar acid is not sufficiently demonstrated. Several other articles by Lavoisier on the analyses of natural waters mention the statement by Le Roy that earth can pass over with water on distillation, and Lavoisier believed that true salts would volatilise with water more readily than earth. He described determinations of density by a hydrometer (areometre) and unsuccessful attempts to calculate the composition of solutions from the density. The composition was correctly related to the nature of the strata of the earth through which the waters had passed. A constant-immersion hydrometer is fully described in an article on the determination of specific gravity. Lavoisier had some idea that purely physical methods might replace chemical analysis of waters, and as Thomson said, chemical analyses were not the investigations in which Lavoisier excelled . 

When a mixture which distils without change of composition is formed, and its boiling point is far below that of the more volatile component, as in the case of normal propyl alcohol and water, or of methyl alcohol and benzene, or far above that of the less volatile component as with nitric acid and water, it is usually possible to separate in a pure state both the mixture of constant boiling point and that component which is in excess. But, if the boiling point of the mixture is very near that of one of the two components, as in the case of ethyl alcohol and water (Fig. 71), or of normal hexane and benzene, it is practically impossible to separate that component in a pure state, and it may be impossible to separate the mixture of constant boiling point even when the component which boils at a widely different... 

The aquation kinetics of the chloropentaamminecobalt(III) ion in water-ethanol mixtures has been studied. The rate constants correlate well with the Grunwald-Winstein Y parameter and with the dielectric constant of the medium. The data supports a D mechanism for the reaction. The loss of chloride from the complexes cw-[Co(en)2(NH2CH2CH20H)Cl] and cw-[Co(en)2(NH2(CH2)3 0H)Cl] has been studied in aqueous ethyleneglycol at 40-65 °C in acidic media and at 20-35 °C in basic media.The rate constants decreased linearly with the increasing mole fraction of the cosolvent. The loss of chloride resulted in the formation of the chelated amino-alcohols as the main product. The observed solvent isotope effect (A h2oAd2o) = 112 at 50 °C, [HCIO4] =0.01 moldm for chloride release is lower than the value reported for the aquation of the cw-[Co(en)2(alkylamine)Cl] complexes (1.38-1.44). This result may indicate the lack of direct solvent intervention in the act of substitution at the cobalt(III) center, as expected for a true intramolecular reaction. 

The apparatus required is similar to that described for Diphenylmelhane (Section IV,4). Place a mixture of 200 g. (230 ml.) of dry benzene and 40 g. (26 ml.) of dry chloroform (1) in the flask, and add 35 g. of anhydrous aluminium chloride in portions of about 6 g. at intervals of 5 minutes with constant shaking. The reaction sets in upon the addition of the aluminium chloride and the liquid boils with the evolution of hydrogen chloride. Complete the reaction by refluxing for 30 minutes on a water bath. When cold, pour the contents of the flask very cautiously on to 250 g. of crushed ice and 10 ml. of concentrated hydrochloric acid. Separate the upper benzene layer, dry it with anhydrous calcium chloride or magnesium sulphate, and remove the benzene in a 100 ml. Claisen flask (see Fig. II, 13, 4) at atmospheric pressure. Distil the remaining oil under reduced pressure use the apparatus shown in Fig. 11,19, 1, and collect the fraction b.p. 190-215°/10 mm. separately. This is crude triphenylmethane and solidifies on cooling. Recrystallise it from about four times its weight of ethyl alcohol (2) the triphenylmethane separates in needles and melts at 92°. The yield is 30 g. 

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