Benzoic acid separation from other compounds

How could we separate a mixture of benzoic acid and cyclohexanol Both compounds are organic, and as a result, both are soluble in an organic solvent such as CH2CI2 and insoluble in water. If a mixture of benzoic acid and cyclohexanol were added to a separatory funnel with CH2CI2 and water, both would dissolve in the CH2CI2 layer, and the two compounds would not be separated from each other. Is it possible to use extraction to separate two compounds of this sort that have similar solubility properties ... 

As mentioned earlier, the control of properties in a supercritical fluid can allow separation to be incorporated into a recrystallisation process. This uses the so-called crossover effect, which arises when the isotherms of solubility versus pressure for two compounds at the same temperature can cross, i.e. the solubility of one compound is greater at a lower temperature, whereas that of the other compound is higher at a higher temperature, and they are equal at an intermediate temperature. Chimowitz et al. [103], by expansion of the solution from an extraction vessel down to 1 bar, measured solubility of 1 10 w/w decanediol-benzoic acid mixture in supercritical carbon dioxide. They experimentally defined the crossover behaviour for the two compounds, and subsequently achieved the separation of almost pure benzoic acid [104] from the 1 10 w/w decanediol-benzoic acid mixture. In a subsequent study, Sako et al separated phenanthrene and naphthalene to 97 wt% purity from a 1 1 w/w mixture using a similar technique [105]. 

Separations based upon differences in the chemical properties of the components. Thus a mixture of toluene and anihne may be separated by extraction with dilute hydrochloric acid the aniline passes into the aqueous layer in the form of the salt, anihne hydrochloride, and may be recovered by neutralisation. Similarly, a mixture of phenol and toluene may be separated by treatment with dilute sodium hydroxide. The above examples are, of comse, simple apphcations of the fact that the various components fah into different solubihty groups (compare Section XI,5). Another example is the separation of a mixture of di-n-butyl ether and chlorobenzene concentrated sulphuric acid dissolves only the w-butyl other and it may be recovered from solution by dilution with water. With some classes of compounds, e.g., unsaturated compounds, concentrated sulphuric acid leads to polymerisation, sulphona-tion, etc., so that the original component cannot be recovered unchanged this solvent, therefore, possesses hmited apphcation. Phenols may be separated from acids (for example, o-cresol from benzoic acid) by a dilute solution of sodium bicarbonate the weakly acidic phenols (and also enols) are not converted into salts by this reagent and may be removed by ether extraction or by other means the acids pass into solution as the sodium salts and may be recovered after acidification. Aldehydes, e.g., benzaldehyde, may be separated from liquid hydrocarbons and other neutral, water-insoluble hquid compounds by shaking with a solution of sodium bisulphite the aldehyde forms a sohd bisulphite compound, which may be filtered off and decomposed with dilute acid or with sodium bicarbonate solution in order to recover the aldehyde. 

Xiao-Hua Yang et al. [ 1 ] determined nanomolar concentrations of individual low molecular weight carboxylic acids (and amines) in seawater. Diffusion of the acids across a hydrophobic membrane was used to concentrate and separate carboxylic acids from inorganic salts and most other organic compounds prior to the application of ion chromatography. Acetic propionic acid, butyric-1 acid, butyric-2 acid, valeric and pyruvic acid, acrylic acid and benzoic acid were all found in reasonable concentrations in seawater. 

In the synthesis of n-talose, Pigman and Isbell succeeded in separating a small quantity of talose monobenzoate from the action of perbenzoic acid on galactal. It gave a positive color test for benzoic acid only after acid hydrolysis and was therefore not a molecular compound of talose and benzoic acid. The method used for the preparation of talose. monobenzoate eliminated any position for the benzoyl residue other than carbon atoms 1 and 2, but the properties of the monobenzoate were different from those which might be anticipated for a normal talose 1- or... 

Phthalic acid and anhydride in systems involving naphthoquinones phthalic determined in 0.1 M HCl at 274 m/x with little interference from maleic. Acids were precipitated as barium salts in alcohol to separate them from naphthoquinones and other interfering compounds Phthalic acid and anhydride in systems involving naphthoquinones after 17 hr in methanol, phthalic esterifies, does not then interfere with the determination of naphthalene at 311 m/x naphthoquinone determined on fresh solutions at 347 m/x, working in red light to avoid photochemical changes. Mixtures also contained benzoic acid, maleic anhydride... 

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