THE REACTIVITY OF THIOLS IN HYDROGEN-ISOTOPE EXCHANGE-REACTION

In order to reveal the reactivity of thiols, the hydrogen-isotope exchange reaction (liquid-solid reaction) between one of thiols dissolved in p-xylene and poly(vinyl alcohol) labeled with tritium was observed at 50 approximately 90-degrees-C. The rate constants ( k ) for the thiol have been obtained with both the A''-McKay plot method and data obtained. Several k for other thiols have been obtained with the same method as above. Comparing these k (and k obtained previously) with each other, the following seven matters have been clarified. (1) The reactivity of benzenethiol increases with temperature. (2) Both the reactivity of benzenethiol and the temperature dependence of the reactivity is similar to that of phenol (and benzoic acid). (3) Benzenethiol is more reactive than cyclohexanethiol and 1-hexanethiol. (4) The reactivity of a certain aliphatic thiol changes with both the length of the straight-chain alkyl group in it and its isomerism. (5) It seems that the reactivity of aliphatic (or alicyclic) thiols follows the Taft's equation. (6) The reactivity of aliphatic (and alicyclic) thiols can be enhanced with one of the substituents (which have the electron attractive effect) since the gradient of the straight line (in the plot based on the Taft's equation) for these thiols in the reaction is greater than zero. ( 7 ) It can be assumed that the effect of the polar effect on the reactivity of the aliphatic compounds is larger than the effect of the steric one on that.