Chemical and Physical Factors which Control the Substitution Reactions of Direct Fission-Produced lodine with Gaseous Methane and the Methyl Halides

Reactions of β¯-Decay Iodine Fission Products with CH4 and CH3X

“…The comparisons of the reaction probabilities of the indirectly produced *I with directly produced *I as reported in reference [1 ], indicates that steric factors are much more important in direct reactions.…”

“…The exact manner in which this was accomplished is outlined in detail in ref. [1 ]. The indirect reaction probabilities were also divided by the number of atoms on the CH3X available for substitution to yield the product molecule.…”

“…It was shown [1 ] that the directly produced *I (withmuch higher translational kinetic energies) reacts with the CH3 X to replace X in a relationship directly proportional to the cross-sectional area of X; likewise, H is replaced with a probability which is inversely proportional to the volume When this mechanistic approach is applied to the reactions of and CH3X, a series of reactions such as those shown in reactions (5) through (9) result. There are other reactions similar to (8) and (9) The initial interaction of with the orpnic molecule leading to formation of the intermediate (reaction (5)) is of an electrostatic or ion-dipole character [29].…”

“…In a previous report [1 ], we hypothesized that the extent of I-for-H and I-for-X reactions of direct-fission-produced iodine with CH4 and CH3X (X = F, Cl, Br and I) are not controlled by conventional chemical factors such as electronegativity and bond energies. Rather the physical steric effects appeared to be the dominant factors Controlling the reactions.…”

Recent Developments in Gas-Phase Hot Atom Chemistry

“…Each system seems a law unto itself and we must look to Professor RACK in his talk later in this conference for guidance. Others who have studied recoil iodine reactions during the past few years include KLKUCHI and CHURCH [43] who showed that fission produced 131 1 gave small yields of CH 3 131 I and CH 2 X 131 1 from substituted methanes (CH 3 X, X = H, F, CI, Br and I) and that the efficiency of the reaction I + C-X ->· C-I + X appeared to increase as did the mass of X. In a moderator study [44] of (η, γ) 128 1 with methyl iodide the yield of CH 3 128 1 was reduced by added neon in a way tractable to an Estrup-Wolfgang analysis, suggesting that this reaction at least was due to translational excitation.…”