Kinetics of Reaction between Phthalic Acid and Potassium Peroxydisulphate-Part I.

The reaction has been carried out in H2SO4 medium in the presence of AgNO3 as catalyst. The reaction is first order w.r.t. [S2O8"]c and zero order w.r.t. [phthalic acid] but the rate constant decreases with an increase in K2S2O8 concentration, according to the relationship -log k = 2·65+ 13·33 [S2O8"]c The rate is only slightly increased on increasing the concn. of H2SO4, while there is great increase with the increase in AgNO3 concentration, the rate expression being of the form \(\frac{\mathrm dx}{\mathrm dt}\) = kCAg+X CS2O8" The reaction is characterised by a low energy of activation (6·0 Kcals/mole), abnormally low frequency factor (0·2708 litre mole-1 sec.-1 ) and a large negative entropy of activation ( -28·390 E.S.U.). A yellow product soluble in acetone, glacial acetic acid, hot ethyl alcohol and in sodium hydroxide was obtained which chars and does not give any sharp m.p. The separation of the different reaction products by paper chromatography or by T.L.C. has not been successful so far