Details

Autor(en) / Beteiligte

• Tanaka, K
• Mackay, G. I
• Payzant, J. D
• Bohme, D. K

Titel

Gas-phase reactions of anions with halogenated methanes at 297 ± 2 K

Ist Teil von

• Canadian journal of chemistry, 1976-05, Vol.54 (10), p.1643-1659

Ort / Verlag

Ottawa, Canada: NRC Research Press

Erscheinungsjahr

1976

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• The rate constants for a number of exothermic displacement (S N 2) reactions of the type X −  + CH 3 Y → Y −  + CH 3 X where X −  = H − , O − , C − , F − , S − , Cl − , OH − , C 2 − , CN − , SH − , S 2 − , C 2 H − , NH 2 − , NO 2 − , CHF − , CH 2 Cl − , CH 2 Br − , CH 3 O − , CH 3 S − , and CH 3 NH − and Y = F, Cl, and Br, have been measured in the gas phase at 297 ± 2 K using the flowing after-glow technique. These gas-phase measurements provided an opportunity to determine the intrinsic nucleophilic reactivity of 'nude' anions and hence to assess the role of solvation in the kinetics of S N 2 reactions proceeding in solution. Comparisons of the experimental rate constants with rate constants calculated using classical theories of capture indicate that several displacement reactions may possess large intrinsic energies of activation, . Correlations were found between apparent activation energies and the heats of reaction. These correlations provided a convenient classification of the various anion nucleophiles. Displacement was observed to compete with proton transfer in reactions involving nucleophiles of high intrinsic basicity and with hydrogen atom transfer and H 2 + transfer in the reactions of the O − radical anion.