The role of hydrogen bonding on kinetics of rearrangement of heterocyclic aldoximes in perchloric acid

Abstract EN

Four paris of syn and anti aromatic heterocyclic aldoximes as 2-thiophenealdoxime, 2-furfuralaldoxime, 2-pyridineaIdoxime and 2-pyrroleaIdoxime are prepared.

The strcutures of these geometrical isomers are confirmed by the measurements of their U.V, I, R and melting points.

Experiments show the existence of these aldoximes in an intramolecular hydrogen bonding with variable strength depending on the hetero atoms in the aldoximes.

The first order rate constants of the rearrangement of syn aldoximes follow the order of hetero S>0>N, while the anti aldoximes show irregular order.

Factors governing the anti constants of the rearrangement of syn and anti aldoximes are analysed.

Activation parameters are estimated and discussed on the basis of isokinetic relation-ship.

The differences in physical and spectroscopic behavior of aldoximes lead to an important suggestion regarding the configuration of oxime.