Water NaBr system, methanol

Another type of ternary electrolyte system consists of two solvents and one salt, such as methanol-water-NaBr. Vapor-liquid equilibrium of such mixed solvent electrolyte systems has never been studied with a thermodynamic model that takes into account the presence of salts explicitly. However, it should be recognized that the interaction parameters of solvent-salt binary systems are functions of the mixed solvent dielectric constant since the ion-molecular electrostatic interaction energies, gma and gmc, depend on the reciprocal of the dielectric constant of the solvent (Robinson and Stokes, (13)). Pure component parameters, such as gmm and gca, are not functions of dielectric constant. Results of data correlation on vapor-liquid equilibrium of methanol-water-NaBr and methanol-water-LiCl at 298.15°K are shown in Tables 9 and 10. 

Table 9. Vapor-Liquid Equilibrium Data Correlation for Methanol-Water-NaBr system at 298.15°K... 

Figure 5. Activity coefficients for methanol and water in NaBr system...

Furter [91] has analyzed the state of the art from the point of view of employing the salt effect in industrial processes, especially in extractive distillation. In addition, he ha.s made up a list of references covering the years 1966 to 1977 [91 a]. Schubert et al. [92] investigated the effect of some metal chlorides and other salts on the isothermal = 60°C) phase equilibrium behaviour of the systems n-propanol-water, n-butanol-water and methanol-water. Using CH30H/H20/NaBr as an example, the method of predicting salt effects for vapour-liquid equilibria as developed by Schuberth has been extended to uusaturated solutions [92a]. 

Included among the salts chosen for study were those that cause salting-out (NaBr, NaF, KCl, Li Cl) and salting-in (HgC ) of methanol in aqueous solutions. To test the technique described above, the vapor-liquid equilibria of systems of constant ratios of salt to solvent 2 were measured. For example, in cases where methanol is salted out, the experiments were done at constant salt-to-water ratios, and when methanol is salted in (salting-out of water), constant salt-to-methanol ratios were used. This was done by preparing a solution of a fixed salt molality and using it as component 2 in the equilibrium still. Thus, references to molality refer to the ratio moles of salt to 1000 g of solvent 2. 

Bis(acyloxy)iodo]arenes in the presence of bromide anion in water also oxidize primary and secondary alcohols similarly to the (PhIO) /KBr system [11,12]. The oxidation of primary alcohols using ArI(OAc)2/KBr in water or aqueous methanol affords carboxylic acids or esters [9, 13], while the oxidation of secondary alcohols under similar conditions results in the formation of the respective ketones in excellent yields [14]. Aldehydes can be converted into methyl esters by a similar procedure using PhI(OAc)2/NaBr in an acidic aqueous methanol solution [15]. Likewise, acetals 3 can be converted into the corresponding hydroxyalkyl carboxylic esters 4 by oxidation with PhI(OAc)2/LiBr in water (Scheme 6.3) [16]. 

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