THE EFFECTS OF SUBSTITUENS AND SOLVENT POLARITY ON PHOTOCHEMICAL SIGMATROPIC SHIFTS. EXPERIMENTAL EVIDENCE IN FAVOUR OF THE OCCURRENCE OF SUDDEN POLARIZATION IN ACYCLIC ALKENES

Article abstract of DOI:10.1016/S0040-4020(01)86197-4

Furher experimental evidence regarding the occurence of sudden polarization in acyclic alkenes is presented.It is shown that the yield of formation of the product derived from an intramolecular photochemical <1,3>-OH shift in the 1 is dependent only on the polarity of the solvent employed.This result could be well explained in terms of a stabilization of the zwitterionic intermediate formed upon irradiation of 1 by reorientation polarization of the dipole solvent molecules.Besides this, it was found that replacement of the alkyl group at the terminal carbon atom of the C3-C9 exocyclic double bond in 1 by a phenyl substituent led to the occurence of a photochemical <1.3>-H shift.This directive effect of the substituents at the exocyclic double bond could be well explained on the basis of the sudden polarization model.