15min:

NICOLA M TONGE, EWAN C MAC MAHON AND MARTIN C R COCKETT, University of York, Department of Chemistry, Heslington, YO10 5DD, United Kingdom.

The study of ionised molecular clusters provides an insight into ion-molecule chemistry; ubiquitous in atmospheric, flame and plasma processes. The neutral fluorobenzene-ammonia system, essentially unreactive in the gas phase, will react in solution under high temperature and pressure conditions. However, fluorobenzene⁺ will react, via nucleophilic substitution to form aniline⁺ and HF. In combination with the aquisition of REMPI spectra, we have observed the following reactions, post-ionisation, of fluorobenzene⁺-(NH₃)_n (n=1,2) clusters:

C₆H₅F⁺.(NH₃)₂ C₆H₅NH₂⁺

C₆H₅F⁺.NH₃ NH₃⁺ + C₆H₅F

While nucleophilic substitution satisfactorily accounts for the formation of aniline⁺, it is more difficult to rationalise the formation of NH₃⁺ on thermodynamic grounds. By performing ab initio calculations we hope to be able to postulate a mechanism for this reaction.