β-Elimination of 9-fluorenylmethanol in solutions of methanol and t-butyl alcohol
Abstract
In solutions of methan[2H1]ol containing sodium methoxide, β-elimination of 9-fluorenylmethanol occurs by an E1cB mechanism. The rate of β-hydrogen exchange exceeds that of elimination and the mechanism is established in a manner similar to that for the reaction in D2O, by analysis of the kinetic induction period upon elimination of undeuteriated substrate in deuteriated solvent. In CH3OH, as in H2O, there are indications of a competing elimination mechanism, probably E2. Addition of t-butyl alcohol to methanol leads to an increase in the absolute rates of exchange and elimination and a decrease in their relative rates. In pure t-butyl alcohol, exchange is completely suppressed, and comparison of both the relative rates of tritium exchange of [9-3H1]9-fluorenylmethanol and [9-3H1]fluorene, and the isotope effect upon elimination, with values in other solvents suggests that elimination occurs via rate-determining formation of a carbanion intermediate.