Specific rates of some reactions of the solvated electron in liquid ammonia measured by pulse radiolysis at 23°C

Abstract

An experimental procedure is described for measurement by nanosecond pulse radiolysis of specific reaction rates of e − am with solutes in liquid ammonia at 23°C. The measured specific rates, in units of dm 3mol −1s −1, follow in parentheses after each solute: anthracene (3·5×10 11), nitrobenze (2·8×10[su11]), phenanthrene (2·3×10 11), naphthalene (1·5×10 9), acetone (1·7×10 8) and (1·1 × 10 11), dichloromethane (1·2 × 10 11), 1,2-dichloroethane (1·5 × 10 9, acetone (1·7 × 10 8) and 1-chloropropane (1·1 × 10 7). For 18 other solutes an upper limit for the specific rate is given. The upper limit for reaction of e am - with NH 4 + at zero ionic strength is estimated to be 1·6 × 10 8 dm 3 mol −1 s −1. Application of the Smoluchowski-Debye equation for diffusion-controlled reactions to reactions of e am - with a univalent positive ion (model ion NH 4 +), a univalent negative ion (model ion NO 3 -), and a neutral species (assumed radius 3·5 Å) gives 1·4 × 10 12, 2·9 × 10 9 and 2·9 × 10 11 dm 3 mol −1 s −1, respectively, for the specific rates at 25°C. The transient absorption spectrum induced in neat (pure) liquid ammonia at 23°C by nanosecond pulse radiolysis is given for the wavelength range 0·25–1·93 microm. A transient absorption with a peak at 0·38 microm grows for 60 ns after the pulse, and is ascribed to a product of a non-homogeneous process. The absorption spectrum for phenanthrene negative ion in liquid ammonia at 23°C, in the wavelength range 0·38–0·55 microm, is given and calculation of the extinction coefficient at 0·447 microm, wavelength of maximum absorption, gives 8·60 × 10 2 m 2 mol −1.