Acids organic, dissociation constant

Acetyl peroxide, 164, 245, 295, 338 Acetyltriallyl citrate, MA copolymerization, 297 2-Acetyl-2,5,6-trimethyl-2,3-dihydropyran, 322 Acid chlorides, dehydrating agent, 86, 89 Acids, organic, dissociation constants, 74, 75 Acridine, 131... 

L. Finston and A. C. Rychtman A New View of Current Acid-Base Theories, Wiley, Chichester, 1982. [108] F. Strohbusch Neue Erkenntnisse der Sdure-Basen-Theorie, Chemie in unserer Zeit 16, 103 (1982). [109] R. A. Cox and K. Yates Acidity Eunctions - An Update, Can. J. Chem. 61, 2225 (1983). [110] (a) E. P. Serjeant and B. Dempsey Ionisation Constants of Organic Acids in Aqueous Solution, Pergamon Press, Oxford/U.K., 1979 (b) K. Izutsu Acid-Base Dissociation Constants in Dipolar Aprotic Solvents, Blackwell Scientific Publishers, Oxford/U.K., 1990. 

Carboxylic and sulfonic acid groups are the two most common structures that impart acidity to organic compounds. Most carboxylic acids have dissociation constants that range between 10 " and 10 , and thus these compounds are readily titrated. An indicator that changes color in a basic range, such as phenolphthalein, is required. 

Depending on the mole ratio of reactants used, the polyacetals have either both terminal vinyl groups, both terminal hydroxyl groups, or one vinyl ether and one hydroxyl group. The reaction can be run at -10° to 20°C using acid salts of strong acids, e,g, alkali metal bisulfate or a-haloethers. Organic acids with dissociation constants of 10 to 10 are used if a reaction temperature of 20°-180°C is desired. 

A sample contains a weak acid analyte, HA, and a weak acid interferent, HB. The acid dissociation constants and partition coefficients for the weak acids are as follows Ra.HA = 1.0 X 10 Ra HB = 1.0 X f0 , RpjHA D,HB 500. (a) Calculate the extraction efficiency for HA and HB when 50.0 mF of sampk buffered to a pH of 7.0, is extracted with 50.0 mF of the organic solvent, (b) Which phase is enriched in the analyte (c) What are the recoveries for the analyte and interferent in this phase (d) What is the separation factor (e) A quantitative analysis is conducted on the contents of the phase enriched in analyte. What is the expected relative erroi if the selectivity coefficient, Rha.hb> is 0.500 and the initial ratio ofHB/HA was lO.O ... 

The physical properties of cyanoacetic acid [372-09-8] and two of its ester derivatives are Hsted ia Table 11 (82). The parent acid is a strong organic acid with a dissociation constant at 25°C of 3.36 x 10. It is prepared by the reaction of chloroacetic acid with sodium cyanide. It is hygroscopic and highly soluble ia alcohols and diethyl ether but iasoluble ia both aromatic and aUphatic hydrocarbons. It undergoes typical nitrile and acid reactions but the presence of the nitrile and the carboxyUc acid on the same carbon cause the hydrogens on C-2 to be readily replaced. The resulting malonic acid derivative decarboxylates to a substituted acrylonitrile ... 

Physical properties of the acid and its anhydride are summarized in Table 1. Other references for more data on specific physical properties of succinic acid are as follows solubiUty in water at 278.15—338.15 K (12) water-enhanced solubiUty in organic solvents (13) dissociation constants in water—acetone (10 vol %) at 30—60°C (14), water—methanol mixtures (10—50 vol %) at 25°C (15,16), water—dioxane mixtures (10—50 vol %) at 25°C (15), and water—dioxane—methanol mixtures at 25°C (17) nucleation and crystal growth (18—20) calculation of the enthalpy of formation using semiempitical methods (21) enthalpy of solution (22,23) and enthalpy of dilution (23). For succinic anhydride, the enthalpies of combustion and sublimation have been reported (24). 

The protonation equilibria for nine hydroxamic acids in solutions have been studied pH-potentiometrically via a modified Irving and Rossotti technique. The dissociation constants (p/fa values) of hydroxamic acids and the thermodynamic functions (AG°, AH°, AS°, and 5) for the successive and overall protonation processes of hydroxamic acids have been derived at different temperatures in water and in three different mixtures of water and dioxane (the mole fractions of dioxane were 0.083, 0.174, and 0.33). Titrations were also carried out in water ionic strengths of (0.15, 0.20, and 0.25) mol dm NaNOg, and the resulting dissociation constants are reported. A detailed thermodynamic analysis of the effects of organic solvent (dioxane), temperature, and ionic strength on the protonation processes of hydroxamic acids is presented and discussed to determine the factors which control these processes. 

The influence of NH., and CO, on the chromatographic behaviour of benzoic acid and its derivatives (o-, m-, p-hydroxybenzoic, nitrobenzoic, aminobenzoic, chlorobenzoic acids) was studied. The work was carried out by means of upgoing TLC on Sorbfil plates. Isopropanol- and ethyl acetate-containing water-organic eluents were used as mobile phases in the absence or presence of gaseous modifiers in the MP. The novel modification of TLC has been found to separate benzoic acids with different values of their dissociation constants more effectively than water-organic mobile phases. 

G. Kortiim, W. Vogel and K. Andrussow, Dissociation Constants of Organic Acids in Aqueous Solution, Butterworths, London, 1961. 

In recent years various attempts have been made to account for the observed differences between the dissociation constants of organic acids, whose molecules differ only slightly from each other. The proposed explanations have naturally been given in each case in terms of the structures of the respective neutral acid molecules.1 In the tentative discussion of HN03 and HI03 that has just been given, the approach has been quite different we focused attention, not on the neutral molecule or on the structure of the anion, but on the condition of the solvent in the vicinity of the anion. 

The theory of titrations between weak acids and strong bases is dealt with in Section 10.13, and is usually applicable to both monoprotic and polyprotic acids (Section 10.16). But for determinations carried out in aqueous solutions it is not normally possible to differentiate easily between the end points for the individual carboxylic acid groups in diprotic acids, such as succinic acid, as the dissociation constants are too close together. In these cases the end points for titrations with sodium hydroxide correspond to neutralisation of all the acidic groups. As some organic acids can be obtained in very high states of purity, sufficiently sharp end points can be obtained to justify their use as standards, e.g. benzoic acid and succinic acid (Section 10.28). The titration procedure described in this section can be used to determine the relative molecular mass (R.M.M.) of a pure carboxylic acid (if the number of acidic groups is known) or the purity of an acid of known R.M.M. 

FIG. 4 Thermodynamic equilibria for the interfacial distribution of a solute X which can be ionized n times, and X being its most acidic (or deprotonated) and its most basic (or protonated) forms, respectively. X and are the dissociation constants in the aqueous and organic phase, respectively, and P is the partition coefficient of the various species between the two phases. 

Superior antimicrobial activity in alkaline pH (seawater is always above pH 8), in the presence of nitrogenous organic matter, and due to lower volatility has been documented for bromine antimicrobials3 4. The pKa acid dissociation constants for HOC1 and HOBr are 7.4 and 8.7, respectively the dissociated acids are less effective antimicrobials4,5. Undissociated hypohalous acids are more effective because they are far better halogenating agents compared to the dissociated anion (hypohalite). Table 1 shows the effect of acid dissociation on antimicrobial performance in well-controlled laboratory experiments. 

Woolley, E. M. Hepler, L. G., Apparent ionization constants of water in aqueous organic mixtures and acid dissociation constants of protonated co-solvents in aqueous solution, Anal. Chem. 44, 1520-1523 (1972). 

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