title: The diatropic sigma ring currents of [pi2s + pi2s + pi2s] pericyclic transition states.
abstract: 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.
authors.affiliation: School of Chemistry, University of Exeter, Stocker Road, Exeter, UK EX4 4QD.
authors.forename: Remco W A
authors.initials: RW
authors.lastname: Havenith
authors.forename: Leonardus W
authors.initials: LW
authors.lastname: Jenneskens
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Fowler
authors.forename: Erich
authors.initials: E
authors.lastname: Steiner