Trends in alkyl substituent effects on nucleophilic reactions of carbonyl compounds: gas phase reactions between ammonia and R1R2COCH3+ oxonium ions.
The reactivity of carbonyl substituted methyl oxonium ions (R1R2COCH3+) towards ammonia has been investigated using an FT-ICR mass spectrometer and ab initio calculations. The monosubstituted ions (R1 = H; R2 = H, CH3, C2H5 and i-C3H7) show different reaction patterns with variable degree of: (1) nucleophilic substitution, (2) addition-elimination and (3) proton transfer, when reacted with ammonia. In all cases addition-elimination dominates over nucleophilic substitution, and the observed reactions are slow. The trends in reactivity are consistent with the alkyl group's electronic properties, as expressed by a single parameter linear or slightly non-linear model.
Bache-Andreassen
Lihn
L
Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway.
Uggerud
Einar
E