Pulse Radiolysis of Liquids at High Pressures. III. Hydratedhyphen;Electron Reactions Not Controlled by Diffusion

摘要

Specific rates of the reactions ofeaqminus;with hydrogen ion, formamide, acetamide, acetoxime, benzyl alcohol, and 2hyphen;chloroethanol have been measured by pulse radiolysis at 29deg;C and six pressures from atmospheric to 6.4 kbar. The specific rates increase monotonically with increase in pressure to 6.4 kbar except that for the H3Oplus;reaction for which there is no further significant increase above sim;3.5 kbar. Results for the H3Oplus;reaction are consistent with that reaction not being diffusion controlled. The activation volume of each reaction increases with increase in pressure. Such a result is attributed to a decrease in cavity volume of the electron with increase in pressure. Activation volumes, in units of milliliters per mole, at 1 atm and 29deg;C are minus;2.7, minus;10.3, minus;7.0, minus;9.5, minus;9.3, and minus;8.2 for the reactions with H3Oplus;, formamide, acetamide, acetoxime, benzyl alcohol, and 2hyphen;chloroethanol, respectively. Interpretation of the activation volumes gives a partial molal volume of 7 ml moleminus;1and, with an electrostriction volume of 3 ml moleminus;1, a cavity volume of 10 ml moleminus;1for the electron in water at 1 atm and 29deg;C. A previous estimate ofVmacr;lpar;eaqminus;rpar; equals; 0thinsp;ml moleminus;1, based on study of competitive reactions ofeaqminus;by ggr; radiolysis at high pressures, is reconciled with the value ofVmacr;lpar;eaqminus;rpar; equals; 7thinsp;ml moleminus;1.