Poly basic Acids

N-Benzylamides are recommended when the corresponding acid is liquid and/or water-soluble so that it cannot itself serve as a derivative. Phe benzylamides derived from the simple fatty acids or their esters are not altogether satisfactory (see Table below) those derived from most hydroxy-acids and from poly basic acids or their esters are formed in good yield and are easily purified. The esters of aromatic acids yield satisfactory derivatives but the method must compete with the equally simple process of hydrolysis and precipitation of the free acid, an obvious derivative when the acid is a solid. The procedure fails with esters of keto, sul phonic, inorganic and some halogenated aliphatic esters. 

Decarboxylation of Di- and Poly-basic Acids (Malonic Ester Synthesis)... 

J This polarization along aliphatic chains forms the only explanation of the dissociation constants of organic acids, in particular of the effect of substituents, and must also, according to N. Bjerrum Zeitschr. f. phys. Chemie 106, 220 (1923)), be taken into account in the theoretical explanation of the dissociation constants of poly basic acids. Quantitative limits to the magnitude of this effect may be obtained by experimenting with different solvents (L. Ebert, Ber. d. dtsch. chem. Ges., 175 (1925)) for short chains its value is fgund to be considerable. 

Chromic hydroxide is an amphoteric compound and exhibits acidic properties in combining with basic oxides to form chromites, to which the general formula M-jO.CrjOg is given, and which are isomorphous with the corresiiouding aluminium compounds known as spinels. They may be considered as derived from an acid, HCrOj the monohydrate, CrjOj.HjO, has this empirical formula. From a study of the action of sodium hydroxide on chromium hydroxide for prolonged periods and the rate of the formation of chromate by the oxidation of dissolved chromite, it would appear that the chronlic hydroxide acts as a poly basic acid. 

Poly-carboxy acids or poly-basic acids... 

Corresponding to the poly-hydroxy or poly-acid alcohols are the poly-carboxy or poly-basic acids. The simplest of these poly-basic acids are those containing two carboxyl groups. Such compounds contain two acid hydrogens and are thus di-basic, exactly analogous to the di-basic inorganic acids, e.g., sulphuric acid, HO—SO2—OH. 

As each poly-hydroxy alcohol must have as many carbon groups as it has hydroxyls, so also, a poly-basic acid must have at least as many carbon groups as it has carboxyls and the simplest di-basic acid must be derived from the two carbon hydrocarbon. 

Oxidation Products of Poly-hydroxy Alcohols.—In our study of the mixed poly-substitution products we considered the mixed alcohol-aldehyde and alcohol-ketone compounds and showed that they are intermediate oxidation products between poly-hydroxy alcohols and poly-basic acids (p. 228). To illustrate, when glycerol, tri-hydroxy propane, is oxidized the following products are obtained. 

Fig. 4-8 shows a chromatogram of various organic acids obtained by using a modern membrane-based suppressor system. The acid concentration in the mobile phase determines the retention in the analysis of di-basic and poly-basic acids. It affects the degree of dissociation and, thus, the retention time of the carboxylic acid to be analyzed. In general, a higher resolution is observed with increasing add concentration. This effect... 

The action of a highly ionized acid on the salt of a poly-basic acid, with the formation of a hydrogen salt of the latter, depends upon the same general principle as that stated above, although the case may appear slightly more complex. The action of nitric acid upon calcium phosphate serves as an illustration. 

Other cellulose esters of organic acids, including those of substituted and poly basic acids, have been studied in detail and will be described in sections to follow. Their cost of manufacture is in general greater than that of the more simple esters, and their uses are confined to cases in which special properties are required. 

A whole range of these resins is available. They are produced by the reaction of polyhydric alcohols and poly basic acids. An important use of these resins is in the manufacture of glass fibre reinforced polyester laminates which, in addition to their great strength, have a high heat and corrosion resistance. 

Low-molecular-weight low-viscosity hydroxylated polyesters can be used for this purpose and can be formulated from glycols, higher polyols and poly basic acids. The HS fully alkylated amines fit well into this type of coating system because they have low molecular weight, are of moderate viscosity, carry little or no solvent and thus offer many advantages in HS formulations. 

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