THE NUCLEOPHILIC-ADDITION ELIMINATION-REACTION ON THE CARBONYL GROUP OF PIVALOYL CHLORIDE, S-METHYL THIOPIVALOATE AND 1-PIVALOYL-1,2,4-TRIAZOLE IN THE GAS-PHASE

The nucleophilic addition-elimination reaction on the carbonyl group of the substrates (CH3)3CCOCl, (CH3)3CCOSCH3 and (CH3)3CCON-CH = N-N = CH [(CH3)3CCOTAZ] has been studied using Fourier-Transform Ion-Cyclotron-Resonance (FT-ICR) Mass Spectrometry. The rates of reactions of (CH3)3CCOCl and (CH3)3CCOSCH3 appear to depend on the basicity of the nucleophiles with the more basic ones reacting most rapidly, while the reactions of (CH3)3CCOTAZ with various nucleophiles occur either at the collision rate for exothermic reactions or not at all for endothermic reactions. These results are for (CH3)3CCOCl and (CH3)3CCOSCH3 in agreement with a double-well potential model having the tetrahedral structure as central energy barrier. The results for the substrate (CH3)3CCOTAZ, however, can be explained very well with a single-well potential model, where the tetrahedral structure corresponds to an energy minimum.