Letter | Published:

Relationships Between some Dissociation Constants

Nature volume 159, page 644 (10 May 1947) | Download Citation



IN these Laboratories the fungistatic properties of ethylenic and acetylenic compounds have been studied recently1. Our results indicated that biological activity was connected with the presence of substituents that attract electrons strongly, and led us to a consideration of the dissociation constants of compounds which donate protons (that is, acids as defined in the broadest sense), since these constants form a basis for a comparison of the affinity for electrons of radicals and groups. During the course of this work, relationships were found between certain dissociation constants, which constants are conveniently expressed as Î"F (= â RT.logeK)2 for the reaction RH + Râ + H+ taking place in dilute aqueous solution at 25° C. Although the relationships summarized below are of general application, space here does not permit them to be illustrated by long lists of examples, and so, as far as possible, only the values of Î"F (calories) for the seven acids, H3PO4 (I) + 2,900; H2PO4â (II) + 9,800; HPO4ââ (III) + 16,900; H2SO3 (IV) + 2,4003; HSO3â (V) + 9,8003; HSO4â (VI) + 2,300 and HOCl (VII) + 10,1004,5, have been used in this discussion differ by 7 kgm. cal. Compare (I) and (II); (II) and (III); and (IV) and (V).

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  1. 1.

    , , and , Nature, 158, 876 (1946).

  2. 2.

    Most of the values given for Î"F have been calculated from the dissociation constants shown in Landolt-Bornstein's "Physikalisch-Chemische Tabellen", Berlin (1923) and Supplements (1927), (1931) and (1936).

  3. 3.

    , and , J. Amer. Chem. Soc., 63, 808 (1941).

  4. 4.

    , Chem. Abst., 35, 2784 (1941).

  5. 5.

    , Chem. Abst., 35, 20 (1941).

  6. 6.

    , Z. phys. Chem., A, 182, 42 (1938).

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  1. Imperial Chemical Industries, Ltd., Butterwick Research Laboratories, The Frythe, Welwyn, Herts. Feb. 26.

    • J. C. MCGOWAN


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