The kinetics of proton and deuteron transfer from 1-(4-nitrophenyl)-1-nitroethane to 1,8-diazabicycloundec-7-ene in aprotic solvents

Article abstract of DOI:10.1139/v82-230

1-(4-Nitrophenyl)-1-nitroethane reacts with the base 1,8-diazabicyclo<5.4.0>undec-7-ene (DBU) in both acetonitrile and toluene solvents in a normal second-order proton-transfer reaction, in contrast to its behaviour with the base 2,7-dimethoxy-1,8-bis(dimethylamino)naphthalene in acetonitrile.The primary isotope effect, k_H/k_D = 12.0 at 25 deg in toluene is very similar to that observed by other workers for the reaction of 4-nitrophenylnitromethane with DBU under the same conditions.In acetonitrile solvent a k_H/k_D ratio of 7.8 was found at 25 deg C.The isotope effecs on the activation parameters for the reaction in both solvents indicate that tunnelling of the proton through the potential energy barrier makes a significant contribution to the reaction rate.