Poly basic

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. 

The chromatographic conditions specified produced a chromatogram in which, for Uni-dyme-18-dimer acid, there are four broad peaks corresponding to neutrals, monobasic, dibasic, and poly basic components. Each peak represents the elution of many isomers for example, the dibasic peak is composed of linear, cyclic, and aromatic dimer, each in various geometric, structural, and conformational isomeric forms (the peaks are very broad as a result of the presence of these isomers). 

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. 

It will be evident that if the acids are poly basic, we can imagine available hydrogen atoms replaced one by one. If all the available hydrogen atoms are replaced by bases, the normal salt is obtained if only one of the available hydrogen... 

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. 

A few other poly-basic ring carboxy acids may be mentioned by name and formula only. Mesitylene, I-3-5-tri-methyl benzene, yields a di-carboxy and tri-carboxy acid together with a mono-carboxy acid already referred to. 

As both nitration and sulphonation take place with comparative ease, with either hydrocarbons or acids, and as the nitro compounds yield amino compounds and these yield diazo compounds, with their numerous reactions, in particular the Sandmeyer reaction for obtaining nitriles and as sulphonic acids are easily converted into phenols or nitriles it will be seen that by a combination of these synthetic reactions practically any desired ring-substituted mono-basic or poly-basic ring-carboxy acid may be obtained. 

We have seen from Fig. 3.9 that the buffer capacity is at a maximum at a pH equal to the pK of the weak acid used in the formulation of the buffer system and decreases appreciably as the pH extends more than one unit either side of this value. If, instead of a single weak monobasic acid, a suitable mixture of poly-basic and monobasic acids is used, it is possible to produce a buffer which is effective over a wide pH range. Such solutions are referred to as universal buffers. A typical example is a mixture of citric acid (pJC i = 3.06, pK,2 = 4.78, pK,3 = 5.40), Na HPO (pK, of conjugate acid H2PO4 = 7.2), diethylbarbituric acid (pKji = 7.43) and boric acid (pK i = 9.24). Because of the wide range of pK, values involved, each associated with a maximum buffer capacity, this buffer is effective over a correspondingly wide pH range (pH 2.4-12). 

The ammonium salts of di- and poly-basic adds react in a similar way, e-s- CO-ONH4 CO.NH,... 

With benzenesulphonic add this important reaction does not take place smoothly for this reason the directions for carrying it out practically will be given later in another place (see /3-naphthol). Polyadd phenols may also be obtained from poly-basic sulphonic adds. The formation of m-dioxvbenzene or resordnol from benzenedisul-phonic acid is of practical value ... 

In poly-basic adds, all the carboxyl groups can be replaced by hydrogen. In this way an add may be transformed into the hydrocarbon from which it was derived. In the above case, the potassium salt may be used instead of the calcium salt. 

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. 

Chemical Formula C, 3, N 0 S, molecular Wt 2639 ziconotide is a 25 amino acid, poly-basic peptide containing three disulfide bridges... 

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. 

Carbon acids (e.g. malononitrile), pK.j values, 90 Carbon bases, 96 Carboxylic acids, pKg values aliphatic and alicyclic, 82, 84 aliphatic (Tables), 84, 86 aromatic, 83 aromatic (Table), 85 dibasic, 31,88 dibasic (Table), 89 heterocyclic, 85, 96 phenols, 86 poly basic, 89 Chelation, ix... 

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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