Solubility Relations of Isomeric Organic Compounds. VIII. Solubility of the Aminobenzoic Acids in Various Liquids

Abstract

In a previous paper* 1 there were presented series of measurements of the solubility of the three nitroanilines in water, alcohol, benzene, chloroform, carbon tetrachloride, ether, ethyl acetate and acetone; the corresponding solubility curves for the three isomers are in general very similar, yet differ appreciably in some cases, these differences being evidently somehow correlated with the melting temperature (presumably also with the heat of melting) of the crystalline isomer. These results indicated the desirability of investigating similarly a related series of isomers to learn moie as to the degree of similarity which may be expected in such parallel cases. Consequently we have measured the solubility, in the same solvents, of the three aminobenzoic acids, which differ formally from the nitroanilines only in the substitution of a carboxyl group for a nitro group; in chemical behavior they differ specifically in the pronounced amphoteric character of the aminobenzoic acids in aqueous solution, and in the readiness with which they decompose at elevated temperatures.There are few data available on the solubility of the aminobenzoic acids. Flaschner and Rankin2 determined the solubility of each in water at temperatures ranging in the case of the ortho from 84o, of meta from 66°, of para from 47°, up to the respective melting point; de Coninck3 worked with the meta in water from o°-7o°, and there are scattered data in various solvents at temperatures io°-25°. The solvents used in the work here presented are methyl, ethyl, and butyl alcohol, ethyl acetate, benzene and chloroform; the temperature range is from 25°t o the melting temperature of the respective acid except in the case of butyl alcohol in which fewer measurements were made.The materials used, selected from the purest stock obtainable, were purified as follows:Ortho-aminobenzoic Acid. The C.P. acid was crystallized several times from water at about 80°, boiling water being avoided because at that temperature some decomposition of the acid occurs.4 Norite was used as a decolorizer prior to the first crystallization from water. Finally the acid was crystallized from hot chloroform, which yielded a slightly yellow crystalline material. A white product can be obtained if the acid is sublimed, but * From a part of the dissertation presented to the Graduate

The Solubility of Acetyl-p-toluidine in Various Solvents.

“…It was the object of this work to add a similar series of solubility data for the paraisomer. Similar solubility data for all three isomers of the dihydroxybenzenes (6), nitroanilines (l), aminobenzoic acids (4), and nitrobenzoic acids (2) have also been determined. Pleuger (5) determined the solubility of acetyl-p-toluidine in pure ethyl alcohol, carbon disulfide, and carbon tetrachloride and in mixtures of ethyl alcohol and carbon tetrachloride, carbon disulfide and ethyl alcohol, and ethyl alcohol and water.…”

Isolation of Pharmaceutical Intermediates through Solid Supported Evaporation. Batch Operation Mode

“…Likewise, the solubility of BA compares well with Thati et al 15 who report a solubility in ethanol at 40 °C of 0.810 ± 0.003 g/g solvent; the higher solubility in methanol is due to the higher polarity of the solvent. Lazzel and Johnston 16 give the solubility of PABA in methanol at 40 °C obtained from interpolating their measurements as 0.38 g/g solvent, which is ca. 10% higher than our value.…”

Solvent Design Using a Quantum Mechanical Continuum Solvation Model

“…Experimental data show that ethanol, ethyl acetate, and methanol are the three best solvents in which solubilities have been measured at 298.15 K . Much lower solubilities have been measured in trichloromethane, benzene, and water…”

“…The top 10 solvents for p-aminobenzoic acid are also alcohols, from ethanol to pentanol derivatives, with a similarly narrow range of free energy of solvation values. Experimental data show that ethanol, ethyl acetate, and methanol are the three best solvents in which solubilities have been measured at 298.15 K. 53 Much lower solubilities have been measured in trichloromethane, benzene, 53 and water. 54 For p-chlorobenzoic acid, the top five candidates are alcohols (∆G°s around -12.6 kcal mol -1 ), followed by some carboxylic acids (∆G°s around -9.2 kcal mol -1 ).…”