Dibasic acids titration

Gran plots for other types of titrations. Gran64 gave the equations for dibasic acid titration and for precipication, complex-formation and redox titrations especially for the precipitation and complex-formation titrations the equations are complicated. 

A Dibasic Acid Titration for the Physical Chemistry Laboratory 223... 

The progress of polyester-forming reactions between glycols and dibasic acids is easily followed by titrating the unreacted carboxyl groups in samples removed from the reaction mixture. Simple esterification reactions are known to be acid-catalyzed. In the absence of an added strong acid, a second molecule of the acid undergoing esterification functions as catalyst. The rate of the poly esterification process should therefore be written... 

The solvent 1,2-dichloroethane (e = 10.60 at 20° C) was used by Bos and Dahmen77 in a study of the titrations of mono- and dibasic acids with TMG (tetramethylguanidine) and a few other bases. 

It is possible to titrate an acid with a base in bromine trifluoride solution and to follow the reaction conductimetrically (e.g. BrFgSbFg + KBrF = KSbFg + 2 BrFg). Moreover, with the dibasic acid (BrF2)aSnF6 and JKBrF4 the equivalence point is observed at a 1 2 ratio of acid to base ... 

Quinuclidine N-oxides form O-acylium salts stable to hydrolysis in neutral and acid media [Eq. (1)]. Their sensitivity to alkalies, on the other hand, is very high and they can be titrated as dibasic acids.42... 

These salts have sharp and reproducible decomposition temperatures but no true melting points. They act as dibasic acids when titrated with standard alkali, thymol blue being used as indicator. 

The cis- and trans-isomers of [Pt MeNH(OH) 2(NH3)2] have been synthesized and potentiometric titrations show that both are dibasic.161 The difference between consecutive dissociation constants is much greater for the cis-isomer, which is attributed to ds-interaction of the ligands. In addition [PtCl2(NHMeOH)4] was shown to be tetrabasic, the titration curve behaving as though two dibasic acids were present. 

Pyrophosphoric Acid (p. 171) may be titrated as a dibasic acid to pH =4-0 using methyl yellow, etc. as before also as a tetrabasic acid using phenolphthalein, thymolphthalein or thymol blue in the presence of barium salt. Electrometric titrations have also been performed.1... 

Hydrolysis with aqueous mercuric chloride in the presence of cadmium carbonate removed the thioethoxy groups in ethyl tetraacetyl-thiostreptobiosaminide diethyl mercaptal. Crystalline tetraacetylstrep-tobiosamine was obtained in this manner. Bromine oxidation of tetraacetylstreptobiosamine in the presence of strontium carbonate yielded an acid which, after reacetylation, was obtained as the crystalline pentaacetyl derivative. The analytical data and the results of potentio-metric titrations for this oxidation product, designated pentaacetyl-streptobiosamic acid monolactone, were in agreement with the formula, Ci3Hi6NOio(CH3CO)5, required for a dibasic acid monolactone. A crystalline monomethyl ester of the substance was prepared. The established formula shows that all hydroxyl groups present are acetylated or lactonized. 

Analysis of streptosonic acid monolactone showed a composition corresponding to the formula CsHgOe. The formulation of this compound as a monolj,ctone of a dibasic acid was based on its behavior during potentiometric titration, when neutral equivalents of 175 and 87.5 were... 

Hardcopy printout of titration data for the titration of a dibasic acid with a standard base. Metrohm 636 Titroprocessor... 

It must be remarked, however, that the curves shown in Fig. 3 are hardly typical. Two definite points of inflection are observed for a dibasic acid only if the two ionization constants are of quite different orders of magnitude, Auerbach and Smolczyk7 have shown, theoretically, that the two points of inflection will not appear unless the ratio Ki/E2 is greater than 16. However, it is safe to say that the ratio must be considerably greater than that if the inflection points are to be obtained experimentally with any accuracy. Also, if the two ionization constants are not quite different the values of the constants determined by the potentiometric titration method described above may be somewhat in error, as is shown by the authors just mentioned and by Simms. ... 

Moreover, investigation of the oxoacidic properties of the V2O5 derivatives by the potentiometric titration method with the use of Ni,NiOlYSZ oxygen electrode is reported in Ref. [158]. The data obtained show that V2O5 is a dibasic acid. The potentiometric determination was performed from the base to the acid. The equilibrium constants ipK) corresponding to reactions (1.2.86) and (1.2.87) were equal to —9.3 0.3 and — 8.3 0.3, respectively (in molar fractions). 

For acids like adipic acid there is only one end-point, corresponding to complete neutralisation of the dibasic acid after an amount of base has been added equivalent to twice the number of mol of acid initially present. For other acids such as malonic acid two end-points are found and there seems to be an apparent separation of the end-points. This must not, however, be taken to mean that the two stages of the titration curve can be treated independently. 

This analysis is complex, but follows the pattern given for the dibasic acids. The solutions of the final equations have to be found by successive approximation, or else by computer curve fitting to the whole titration curve. In practice, this is how the analysis will be carried out. 

The titration curve can be analysed as for a dibasic acid, with the two acid groups being the +NH3 group and the COOH group. What the titration curve cannot tell directly is to which grouping each pAT refers, or what the species present at the first equivalence point actually is. This must be found from other studies, spectroscopic analysis being the most powerful. As shown in Section 3.5 there are two possible structures ... 

Unstable crystals, mp 119-120. Turns brown and liquefies on standing. The decompn products are formic acid and N-hydroxyglycine. Dibasic acid, potentiometrie titration shows pH peak at 3.5 and 9.1. Soluble in water, methanol, ethanol, acetone, ether... 

Crystals from water + alcohol, dec 195-197". Titrates as a dibasic acid. Freely soluble in water (1 g dissolves in 3 ml HjO). Practically insol in abs ethanol, ether. Remarkably resistant to hydrolysis by boiling with strong alkali. May be hydrolyzed by boiling with 6jY HCl for 14 hrs. 

The only representative of this category is dicrotalic acid, CeHioOs, from dicrotaline, which was found by titration with standard alkali to be a dibasic acid (4). 

Seneciphyllic acid, isolated upon alkaline hydrolysis of seneciphylline by Konovalova and Orekhov (37), is unusual among the necic acids in that it showed no optical activity. Titration with standard alkali indicated that it is a dibasic acid. A Zerewitinoff determination indicated the presence of two active hydrogens. 

Edsall JT, Martin RB and Hollingworth BR, lonizatin of individual groups in dibasic acids, with application to the amino and hydroxyl groups of tyrosine, Proc. Natl. Acad. Sci. USA, 44, 505-518 (1958). Cited in Perrin Bases 1961 no. 3304 ref. E7. NB Used a glass electrode in cells with liquid junction potentials. These results were from direct titrations. pK values calculated from ttie measured microconstants were very similar. 

Dibasic acids, polybasic acids, and proteins, with two or more ionizable groups, give more complex titration curves than the sinqile monobasic adds (Schulz, 1994). Consider the titration curve of a simple amino acid which has no charge in its side chain. In aqueous solution, a monoamino, monocarboxylic add is distributed between three species, namely the fully protonated acid, the zwitterion, and the fully dissociated base ... 

On the other hand, the initial symmetrical Pt (II) complexes of dialkyl H-phosphonates can be titrated by base, whereby they behave as dibasic acids [427]. 

The method preferred in practice for determining the content of "free carbon dioxide", hydrogen carbonate ions and carbonate ipns, and thereby the total carbon dioxide content, is to titrate the water sample acidi-metrically. Carbonic acid is a dibasic acid it dissociates in two stages. The interrelationship which forms the basis of the acidimetric titration... 

Most methods for the determination of carboxyl groups in polymers are based on titration techniques including, for example, the following copolymers acrylic acid-itaconic acid [16], acrylic acid-ethyl acrylate [17] and maleic acid-styrene [18]. High-frequency titration has been applied [19] to the analysis of itaconic acid-styrene and maleic acid-styrene copolymers. The method can also be used to detect traces of acidic impurities in polymers, and in the identification of mixtures of similar acidic copolymers. Titration indicates that the acid segments in the copolymers of itaconic acid-styrene, and maleic acid-styrene, and the homopolymer polyitaconic acid, act as dibasic acids. The method has a sensitivity that permits identification and approximate resolution of two carboxylate species in the same polymer, for example ... 

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