Reactions of Methane with Iodine Activated by Radiative Neutron Capture. II

Abstract

Further experiments have been conducted to clarify the mechanism of the unique reaction whereby I¹²⁸ freshly formed by the I¹²⁷(n,γ)I¹²⁸ process is able to replace hydrogen in methane (I¹²⁸+CH₄→CH₃I+H). They show that the yield of CH₃I¹²⁸ is decreased by the presence of the inert gases He, A, and Xe but not to the extent which would be the case if the activation energy for the reaction were supplied solely by kinetic energy of the I¹²⁸. I₂, CH₃I, C₂H₅I, C₃H₇I and NO, which have lower ionization potentials than that of the I atom are all more effective than the inert gases in reducing the yield. The organic yield of I¹²⁸ is higher when alkyl iodides are used as the source of iodine than when I₂ is used. The ability of the freshly formed I¹²⁸ to react with C₂H₆ or C₆H₆ is much less than with CH₄. Reactions of I₂ with CH₄ sensitized by argon and xenon occur when several hundred mm of the inert gas is present during exposures to 10⁵r or more of gamma radiation.