339. Chemical constitution and the dissociation constants of monocarboxylic acids. Part XIX. Dihydroxy- and dichloro-benzoic acids

Composite hydrolytic dissociation constants, KI and KII, of 4-aminobenzoic acids substituted as follows, 2-H-, 2-C&-, 2-C1-, 2-Br-, 2-N02-, 2-OH-, 2-OCH3-, 3-Br -, 2,6-(CH3)2-, 2,6-(CzH&-, 2,6-Q2 -and 2,6-Bra -, have been determined in aqueous solution, at 50°C and at an ionic strength of 0.1.From the values of PKI and ~K I I and the postulate that the inductive effect of the 4-NH3+ group on the dissociation of the 1-COOH group is the same for all the acids studied, namely 0.54, all four individual pK values have been calculated for each acid as well as the fraction of zwitterion. After comparison of the individual pK values with the correspondingly substituted benzoic acids and anilinium ions, several conclusions could be drawn with respect to the configurational and energetic: relationships between the acids.Hydrolytic dissociation of a protonized amino-acid NH3' RCOOH can occur by way of two different ampholytic species, a "neutral" one NHzRCOOH or, allernatively, a dipolar or zwitterionic species NHs+RCOO-.

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Dissociation of salicylic acid, 2,4-, 2,5-and 2,6-dihydroxybenzoic acids in 1-propanol-water mixtures at 25°C

Papadopoulos

Avranas

1991

J Solution Chem

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339. Chemical constitution and the dissociation constants of monocarboxylic acids. Part XIX. Dihydroxy- and dichloro-benzoic acids

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Electronic effects of ether and hydroxyl groups

Electronic effects of ether and hydroxyl groups

Hydrolytic dissociation constants of substituted 4‐aminobenzoic acids

Dissociation of salicylic acid, 2,4-, 2,5-and 2,6-dihydroxybenzoic acids in 1-propanol-water mixtures at 25°C

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