| Abstract: | The rate coefficients and partial rate factors for the hydrogen-deuterium exchange of some 1-substituted pyrroles (1-substituents = -COCH3, - COC6H5, -SO2CH3, -SO2CF3, -N(CH3)3, -NH(CH3)2, -SO2C6H5) in deuterated trifluoroacetic acid have been determined. In all cases the rate of exchange is faster at the 2-position. Similarly, the hydrogen-deuterium exchange of some pyrroles with electron withdrawing substituents in the 2-position indicate a relative reactivity of 4→ 5→ 3-position with the selectivity being greatest for the more electron withdrawing groups. A nitro group in the 3-position of pyrrole shows a relative reactivity of 5→2→4-position for the hydrogen-deuterium exchange in deuterated trifluoroacetic acid. A linear correlation is observed for the log of the rate coefficient of the hydrogen-deuterium exchange at the 4-position of some 2-substituted pyrroles and the difference in the calculated energy of formation of the pyrrole and the corresponding 4-deuterated cation. |
