Pulse radiolytical investigation of the reversible reaction of biphenyl with the solvated electron in liquid ammonia

Abstract

From the measured solubility of biphenyl in liquid ammonia for the temperature range 21 to - 15.5$sup 0$, 9.4 kcal mole$sup -1$ for the heat of solution and 30 cal deg$sup -1$ mole$sup -1$ for the entropy of solution for a 1 M standard state are calculated. Nanosecond pulse radiolysis of biphenyl solutions in liquid ammonia show that the reaction of e/sub am/$sup -$ with biphenyl produces the biphenyl anion and it is reversible. From the values of the equilibrium constant (the equilibrium concentration of the biphenyl anion divided by the initial concentration of biphenyl and the equilibrium concentration of e$sup -$/sub am) at 21.6 and 10.5$sup 0$, - 20 kcal mole$sup -1$ for the heat of reaction and - 44 cal deg$sup -1$ mole$sup -1$ for the entropy of reaction for a 1 M standard state are calculated. The specific rate of the reaction of e$sup -$/sub am/ with biphenyl is equal to 1.24 x 10/sup (12- 1600/ 2.3RT)/ for the temperature range 21.6 to - 75$sup 0$. The extinction coefficient of the biphenyl anion at 0.403 $mu$, the wavelength of maximum absorption, is 3.1 x 10$sup 4$ M$sup -1$ cm$sup -1$ for the temperature range 23 to -more » 76.5$sup 0$. The calculated values of the standard heat of formation of e$sup -$/sub am/ and the entropy of e$sup -$/sub am/ for a 1 M standard state are - 14 kcal mole$sup -1$ and 13 cal deg$sup -1$ mole$sup -1$, respectively. (auth)« less