The diatropic sigma ring currents of [pi2s + pi2s + pi2s] pericyclic transition states.
Ab initio current-density maps for the (4n + 2)-electron transition states of two thermally allowed [pi2s + pi2s + pi2s] trimerisations, of ethyne to benzene (1), and of ethene to cyclohexane (2), show that both support sigma diatropic ring currents, dominated by four-electron sigma --> sigma* virtual excitation of HOMO electrons.
Havenith
Remco W A
RW
School of Chemistry, University of Exeter, Stocker Road, Exeter, UK EX4 4QD.
Jenneskens
Leonardus W
LW
Fowler
Patrick W
PW
Steiner
Erich
E