Separating the Products of Hydrolysis

The experimental procedure to be followed depends upon the products of hydrolysis. If the alcohol and aldehyde are both soluble in water, the reaction product is divided into two parts. One portion is used for the characterisation of the aldehyde by the preparation of a suitable derivative e.g., the 2 4-dinitrophenylhydrazone, semicarbazone or di-medone compound—see Sections 111,70 and 111,74). The other portion is employed for the preparation of a 3 5-dinitrobenzoate, etc. (see Section 111,27) it is advisable first to concentrate the alcohol by dis tillation or to attempt to salt out the alcohol by the addition of solid potassium carbonate. If one of the hydrolysis products is insoluble in the reaction mixture, it is separated and characterised. If both the aldehyde and the alcohol are insoluble, they are removed from the aqueous layer separation is generally most simply effected with sodium bisulphite solution (compare Section Ill,74),but fractional distillation may sometimes be employed. 

The experimental details already given for the detection and characterisation of aliphatic esters (determination of saponification equivalents h3 diolysis Section 111,106) apply equally to aromatic esters. A sfight modification in the procediu-e for isolating the products of hydrolysis is necessary for i)henolic (or phenyl) esters since the alkaline solution will contain hoth the alkali phenate and the alkali salt of the organic acid upon acidification, both the phenol and the acid will be hberated. Two methods may be used for separating the phenol and the acid ... 

Only in a few cases has this compound been isolated from the products of hydrolysis of proteins, since its separation is extremely laborious. It can only be effected after all the other amino acids have been removed by crystallisation and by the ester method, and after the diamino acids have been precipitated by phosphotungstic acid. From the last mother-liquors it is obtained by crystallisation, and is best identified in the form of its /8-naphthalene sulpho-derivative. 

Organic-soluble ester is brought to the reactor with the organic feed solution and freely permeates the immobilized organic liquid membrane to reach the catalyst enzyme. The ester is then hydrolyzed. The alcohol and acid products of hydrolysis are much more polar than the ester and, as such, are water soluble but relatively organic insoluble. These products diffuse to the aqueous permeate solution. The membrane both provides an active site for the reaction and separates the products of reaction from the feed [38]. 

With the exception of 4-methylxylose all the methyl ethers that are derivable theoretically from D-xylopyranose or D-xylofuranose are known. From the products of hydrolysis of methylated polysaccharides 2-methyl-, 3-methyl-, 2,3-dimethyl-, 2,4-dimethyl-, 3,4-dimethyl- and 2,3,4-tri-methyl-D-xylose have been separated. No D-xylofuranose derivatives have been isolated from a natural source. Unknown at the present time are the 4-methyl-, 4,5-dimethyl-, 2,4,5- and 3,4,5-trimethyl- and... 

Column separations of the products of hydrolysis of carbohydrate boronates by use of anionic resins provides an alternative, efficient means of deboronation,27,67 69 and other similar separations have used columns of cellulose,48 alumina,67 and, for carbonyl-containing compounds, anion-exchange resins in the hydrogensulfite form.53 In special cases, electrophoresis30 and direct crystallization23 have been employed. 

If all the hydroxyl groups are converted into —O.CH3 by methylation, the two end glucose units will each have four methoxy groups compared with three in all the other components in the chain. When the methylated cellulose is hydrolysed, B above breaks down with the loss of one methyl group. There will therefore only be one tetramethyl glucose unit in the product of hydrolysis, and this can be separated by distillation under reduced pressure. There has, however, been some dispute about the accuracy of this method. More recently Wolfram J. Amer. Chetn. Soc. 1937, 1938, 1939) formed mercaptals with the aldehyde structural isomer... 

We might then suspect that the original polysaccharide was composed of separate glucose and galactose chains, with a gluc-gal branching point where one chain joined the other. Alternatively, if the products of hydrolysis were the fragments... 

For anionic surfactants colorimetric methods utilize the formation of an ion pair between the surfactant anion and a cationic dye. Similarly to two-phase titration, colorimetric determination is based on the fact that the ion pair is extractable into organic solvent, while the dye by itself is not. A characteristic example of the analysis of anionic surfactant is the determination of alkylsulfates and alkyl(aryl)sulfonates as their complex with methylene blue extracted into chloroform [31]. The absorbance of chloroform extract is measured at 625 nm versus chloroform background. This methods allows one to analyze alkylsulfates and alkyl(aryl)sulfonates separately. Alkylsulfates, in contrast to sulfonates, are easily hydrolyzed by hydrochloric acid. The products of hydrolysis do not interact with methylene blue and are not transferred into chloroform. Some other cationic dyes, such as dimidium bromide, can also be used. In fact, the use of the latter allows one to achieve much higher sensitivity than that obtained with methylene blue. 

The five fractions separated in Witte peptone are likewise found in the products of hydrolysis, either with adds, or with enzymes of all protein substances The limits of pre-dpitation of the four albumoses, according to their different origins, are given in the following table ... 

For testing nutrition by means of simple amino-adds described above, we have utilized a very complex mixture which greatly resembles the natural products of the hydrolysis of peptones. Most of the substances entering into this mixture have been studied separately, espedally from the point of view of the influence which each may exert on the assimilation of the whole. It has been attempted experimentally to see whether all the products of hydrolysis are indispensable, or whether they can be replaced by each other. Although these tests are very delicate and are diflflcult to perform, they have nevertheless given definite results. Glycin appears to play an entirely secondary part and another add can be substituted for it. On the contrary, tryptophane appears to be a substance that is absolutely necessary. The following is an experiment on this subject ... 

The products of hydrolysis are the separate, individual amino acid molecules. The product of denaturation has the same primary protein backbone with different secondary, tertiary, and quaternary structures. 

Enzymes, carboxypeptidases, or amino peptidases have been found that can release C- and N-terminal amino acids selectively. Chromatography is used to separate the product of enzymic or organic hydrolysis. 

The gradient elution method, with varying concentrations of hydrochloric acid, was employed to separate the products of both types of hydrolysis on the Dowex resin. The products were located among the fractions collected by their color reaction with ninhydrin and by their radioactivity. Final identification of the compounds was made by microacetylation and paper chromatography of selected fractions. Distribution of label in the subunits is summarized in Tables 2 and 3-... 

The residue in the flask will contain the sodium (or potassium) salt of the acid together with excess of alkali. Just acidify with dilute sulphuric acid and observe whether a crystalline acid separates if it does, filter, recrystallise and identify (Section 111,85). If no crystaUine solid is obtained, the solution may be just neutralised to phenolphthalein and the solution of the alkali salt used for the preparation of a crystaUine derivative. This wiU confirm, if necessary, the results of hydrolysis by method 1. If the time factor is important, either method 1 or the product of the caustic alkali hydrolysis may be used for the identification of the acid. 

Separation Processes. The product of ore digestion contains the rare earths in the same ratio as that in which they were originally present in the ore, with few exceptions, because of the similarity in chemical properties. The various processes for separating individual rare earth from naturally occurring rare-earth mixtures essentially utilize small differences in acidity resulting from the decrease in ionic radius from lanthanum to lutetium. The acidity differences influence the solubiUties of salts, the hydrolysis of cations, and the formation of complex species so as to allow separation by fractional crystallization, fractional precipitation, ion exchange, and solvent extraction. In addition, the existence of tetravalent and divalent species for cerium and europium, respectively, is useful because the chemical behavior of these ions is markedly different from that of the trivalent species. 

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