Substitution Reactions of Beryllium (II) Ion in Mixed Solvents. I. The Beryllium Sulphate Complex in Water‐Formamide Mixtures

The formation of the inner‐sphere complex of BeSO4 in mixtures of water and formamide has been investigated using the pressure‐jump relaxation method. Whereas in the two pure solvents the reaction is characterized by a single relaxation time in the solvent mixtures two relaxation processes superimpose and which are attributed to the replacement of a water or a formamide molecule, respectively, in the inner‐sphere by the entering sulphate ion. – The multistep association mechanism proposed by Eigen and Tamm [1] prevails also in the solvent mixtures. With increasing mole fraction of formamide the dielectric constant increases and in accordance with Fuoss equation [2] the association constants of the outer‐sphere complexes decrease. However, the inner‐sphere stability constants increase sharply so that the total association constants of BeSO4. increase with the formamide content. The ligand assisted dissociative process (Id [3]) outer‐sphere r̊ inner‐sphere complex is discussed in terms of a concerted mechanism proposed earlier for aqueous solutions [4].