Ultrafast generation/annihilation dynamics of the tert-butyl carbocation in sulfuric acid as studied by Raman band shape analysis

The ultrafast generation/annihilation dynamics of the tert-butyl carbocation (ultrafast dehydration/hydration dynamics of tert-butyl alcohol) in sulfuric acid has been studied quantitatively by Raman band shape analysis. The two-state exchange model successfully explains the change of the Raman band shape with increasing proton concentration and hence with increasing the rate of dehydration. Highly dynamic nature of the carbocation has been elucidated; in 1 mol dm−3 sulfuric acid, it is generated in timescales of 10 ps, and is annihilated with lifetimes of about 500 fs.