Registration Dossier
Registration Dossier
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EC number: 206-074-2 | CAS number: 299-27-4
Dissociation constant
Administrative data
Link to relevant study record(s)
Description of key information
Information regarding the dissociation constant of potassium gluconate was read-across from that of gluconic acid, which in aqueous solution is in equilibrium with its cyclic esters and its anion. A TGD-approved handbook states that gluconic acid (free acid) has a dissociation constant of 3.6 at 25°C, suggesting that at the ambient pH of 3.6, half the gluconic acid molecules will exist in the form of the uncharged acid, and half as the anion. At pH < 3.6, the undissociated form will predominate, and pH > 3.6 the anion will predominate. Therefore, similar to gluconic acid, potassium gluconate will exist predominantly in the form of the dissociated gluconate anion throughout the range of pH 4 to 9.
Key value for chemical safety assessment
Additional information
Potassium gluconate is a 1:1 salt of gluconic acid, which will dissolve in water to generate potassium cation and gluconate anion. Potassium is a strong base, and as such is expected to remain ionized at essentially any pH, but the gluconate anion deriving from the salt will be subject to the same equilibrium as those deriving from the free acid. Therefore, the gluconate anion is predicted to posses the same pKa of 3.6 as the free acid. In this way, gluconic acid in aqueous solution is in equilibrium with its cyclic esters and its anion, according to the pH of the system, and in any system with sufficient buffering capacity, the effects of introducing equimolar amounts of gluconic acid, D-glucono-δ-lactone, or potassium gluconate would be indistinguishable. Hence these substances are considered to be appropriate surrogates for each other in sufficiently buffered aqueous systems, such as environmental waters, flora and fauna. Information regarding dissociation constant of potassium gluconate was read-across from that of gluconic acid, which was sourced from two separate handbooks. Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (14th Ed.) and Ullmann's Encylopedia of Industrial Chemistry (7th Ed.) report that gluconic acid (free acid) has a dissociation constant of 3.6 and 3.7 at 25°C, respectively. Although the information from both sources is comparable, the data obtained from Ullmann’s handbook is not TGD-approved, and as such is of Klimish-4 reliability and is not considered valid.
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