Methanol ethyl acetate system

The salt effect is attributable to the formation of preferential solvation from the standpoint of molecular structure. In other words, when calcium chloride, which dissolves readily in methanol but very little in ethyl acetate, was added to the methanol-ethyl acetate system to saturation, calcium chloride formed with methanol the preferential solvate which may be written CaCl2 6CH30H. It was also shown from the observation of solubility that the solvated methanol molecules did not participate in the vapor-liquid equilibrium. 

The preferential solvation formed between salt and solvent molecules causes a salt effect on vapor-liquid equilibria. A method of prediction of salt effect based on the preferential solvation number was reported previously for the case in which salt was solved below the saturation level. The idea introduced in this chapter applies for salt solved in saturation. The alcohol-ester-calcium chloride system for which the preferential solvation was thought to be formed was examined. Specifically, calcium chloride dissolves readily in alcohol but only sparingly in ester. Thus, when calcium chloride is solved into alcohol-ester mixed solvent, the calcium chloride will form a preferential solvation with alcohol only. Methanol-methyl acetate, butanolr-butyl acetate, and methanol-ethyl acetate systems were selected for the mixed-solvent systems. 

Figures 4, 5, and 6 indicate caluculated results of the preferential solvation numbers for the three systems. As shown by each figure, preferential solvation numbers are almost constant against compositions of the solvent. On the other hand, the concentration of salt increases linearly against an increase in the concentration of alcohol in the solvent as indicated in Figures 1, 2, and 3. This fact denotes that for an increase of solvent which forms a preferential solvate in a solvent mixture, the salt required to form a certain solvation number with that solvent is dissolved. For essential concentration x1SL in Equations 3 and 4, which are required in calculating solvation numbers, the data observed by the author et al. (I) were used for the methanol-ethyl acetate system ...

Figure 4. Preferential solvation number in the methanol-ethyl acetate system at 1 atm (O), CaCl2 5 wt % (A), CaCl2 10 wt % (V), CaCl2 20 wt % (D)y CaCl2 25 wt % (%), CaCl2 saturated (1).

Similar polymerizations have been carried out at monomer concentrations of 0.2 M/liter using potassium persulfate as the initiator for the polymerization of methacrylic, acrylic, and itaconic acids at 50°C for 5 hr under reduced pressure. In this case, the solid acids were isolated by precipitation from the aqueous solution with ethyl acetate and reprecipitated from a methanol-ethyl acetate system [49]. 

A method of prediction of the salt effect of vapor-liquid equilibrium relationships in the methanol-ethyl acetate-calcium chloride system at atmospheric pressure is described. From the determined solubilities it is assumed that methanol forms a preferential solvate of CaCl296CH OH. The preferential solvation number was calculated from the observed values of the salt effect in 14 systems, as a result of which the solvation number showed a linear relationship with respect to the concentration of solvent. With the use of the linear relation the salt effect can be determined from the solvation number of pure solvent and the vapor-liquid equilibrium relations obtained without adding a salt. 

A mixture of norcodeine hydrochloride (11.48 g, 27.8 mmol), (chloromethyl)cyclopropane (5.14 g, 55.6 mmol), sodium carbonate (14.73 g, 139.0 mmol), and potassium iodide (4.61 g, 27.8 mmol) in ethanol (250 ml) was heated at reflux for 20 hr, cooled, and evaporated in vacuo to dryness. The residue was basified with NH4OH, and extracted with methylene chloride. The extract was washed with water and evaporated in vacuo to dryness. The residue (11.7 g) was chromatographed on silica gel with a eluting solvent system of methanol/ethyl acetate (10/90) to give 17-cyclopropylmethylnorcodeine (10.68 g, 91% yield). 

FIG. 13-95 Number of theoretical stages versus solvent-to-feed ratio for extractive distillation, (a) Close-boiling vinyl acetate-ethyl acetate system with phenol solvent, (b) Azeotropic acetone-methanol system with water solvent. 

The author selected the system containing salt which is not dissolved with other components but only with a particular component of a solvent mixture as a system with which the phenomenon of preferential solvate can be understood easily. Calcium chloride is dissolved with alcohol but it is not dissolved well with ester. Thus, calcium chloride forms a preferential solvate with alcohol and does not with ester. For the component system which consists of calcium chloride, alcohol, and ester, the author selected the following three systems for which vapor-liquid equibrium relations have been measured methanol-ethyl acetate-calcium chloride (I) methyl acetate-methanol-calcium chloride (3) and n-butyl acetate-n-butanol-calcium chloride (3). 

Figures 7, 8, and 9 indicate the prediction results for the following three systems methanol-ethyl acetate, methyl acetate-methanol, and butyl acetate-butanol with saturated calcium chloride, respectively. The absolute value of mean errors At/ were 0.018 and 0.014 for each system, while the maximum and minimum errors were 0.047 and 0, 0.039 and 0.005, and 0.039 and 0.005, respectively.

Figure 7. Result of prediction for methanol-ethyl acetate-calcium chloride system at 1 atm (O), observed (—), calculated.

Sometimes a column will become contaminated with stubborn polar material. Back-washing some columns is possible, but this is not necessarily the best way to treat them. It is better to nm a polar solvent through, such as methanol (or even water), then gradually change the solvent back to a less polar system, through the sequence water methanol ethyl acetate ethyl acetate/petrol petrol. 

For the piuification of the reaction mixtiues, flash-chromatography was used. The solvent was a 35 65 (vol/vol) hexane/ethyl acetate system, and the Revalues are mentioned in Table 10. The chemical structure of the compounds was identified with the aid of NMR spectroscopy. For the deacetylation of compounds [36a-h], sodium in methanol was used. The products were dissolved in a solvent mixture of methanol and dichloromethane (6 1, vol/vol) because the protected glycosyl part of [36a-h] is not soluble in methanol. The FTIR data and yields of compounds [37a-h] are shown in Table 11. 

TLC on silica gel 60 plates was used in various TLC solvent systems for both determination and identification of flavin derivatives in baker s yeast and foods (plain yogurt and bioyogurt, raw egg white, and egg powder). The Rf values of two unknown compounds found in plain yogurt were identical to those of 7a-hydroxyriboflavin (Rf values 0.32 and 0.21) and riboflavin-p-galactoside (Rf values 0.14 and 0.10), but not to those of other flavin compounds [flavin adenine dinucleotide or FAD (Rf values 0 and 0), flavine mononucleotide or FMN (Rf values 0 and 0.05), 10-hydroxyethylflavin (/ f values 0.71 and 0.40), riboflavin (Rf values 0.55 and 0.32), and 10-formyhnethylflavin (Rf values 0.86 and 0.76)] by TLC on silica gel with chloroform-methanol-ethyl acetate (5 5 2) and 1-butanol—benzyl alcohol—glacial acetic acid (8 4 3) as solvents, respectively. ... 

Nagata, I. Isobaiic vapor-liquid equilibria for the ternary system chloroform-methanol-ethyl acetate J. Chem. Eng. Data 1962, 7... 

Pd(II), Rh(III), Ru(III), and Pt(II) were baseline resolved as their 4-(5-nitro-2-pyridylazo)resorcinol complexes using a C g column (A = 536nm) and a 50/10/40 methanol/ethyl acetate/water (lOmM acetate buffer at pH 4.0 with lOmM tetra-butylammonium bromide and 0.01 mM sodium EDTA) mobile phase [155]. Separation was complete in 20 min and detection limits of - 1 ng/mL were reported. A plot of k versus percent methanol ranging from 40% to 90% with no ethyl acetate present was given. The k for some complexes exceeded 9 when the mobile phase contained <50% methanol, so this is probably not an effective system to use. Ethyl acetate was used to enhance the selectivity of the separation. Levels of 4% to 20% ethyl acetate were used to generate baseline separation. 

An additional challenge of biomedical applications of TLC relate to the separations of cyclic nucleotides from noncyclic phosphates. Potter and Yamazaki (48) employed alumina TLC and ammonium acetate pH with ammonium hydroxide to effect these separations. Hynie (49) separated 3 S cGMP using borate impregnated silica in butanol-methanol-ethyl acetate-ammonium hydroxide. Tomasz (SO) separated cyclic pyr/purines on cation exchange, pretreated with HCI, as opposed to the popular anion (PEI) systems. The run with 0.05 M oxalic acid is appealing. 

Akita, K. Yoshida, F. Phase equilibria in methanol - ethyl acetate - water system. J. Chem. Eng. Data 1963, 8, 484-490. 

Nakanishi, K. Nakasato, K. Toba, R. Shirai, H. Vapor-Uquid equilibria of binary systems containing alcohols. Methanol-ethyl acetate and methanol-isopropyl ether. J. Chem. Eng. Data 1967, 12, 440-442. 

Hydrogen peroxide has also been analy2ed by its chemiluminescent reaction with bis(2,4,6-trichlorophenyl) oxalate and perylene in a buffered (pH 4—10) aqueous ethyl acetate—methanol solution (284). Using a flow system, intensity was linear from the detection limit of 7 x 10 M to at least 10 M. 

However, it was not until the beginning of 1994 that a rapid (<1.5 h) total resolution of two pairs of racemic amino acid derivatives with a CPC device was published [124]. The chiral selector was A-dodecanoyl-L-proline-3,5-dimethylanilide (1) and the system of solvents used was constituted by a mixture of heptane/ethyl acetate/methanol/water (3 1 3 1). Although the amounts of sample resolved were small (2 ml of a 10 inM solution of the amino acid derivatives), this separation demonstrated the feasibility and the potential of the technique for chiral separations. Thus, a number of publications appeared subsequently. Firstly, the same chiral selector was utilized for the resolution of 1 g of ( )-A-(3,5-dinitrobenzoyl)leucine with a modified system of solvents, where the substitution of water by an acidified solution... 

---