Microwave spectrum, structure, molecular dipole and quadrupole moments, and magnetic properties of bicyclo[2.1.0]pent-2-ene

Abstract

The labeling results and the small isotope effect on the rate constant for the isomerization rule out the orbital symmetry allowed retro-ene mechanism for the isomerization. They are consistent with the disrotatory, disallowed "biradical" process and with several other plausible formulations. A distinction among three of these is now being sought through the synthesis and rearrangement of bicyclopentene-2,5-c/2.(18) The fair agreement between the present and earlier2•3 kinetic results for unlabeled bicyclopentene, in spite of a threefold increase in the cell's surface-to-volume ratio, argues against a possible hetero-geneous2•3 process.

Orbital mixing rule

“…13 The calculation was carried out on the molecular structure determined by microwave spectra. 21 The electronic feature is consistent with the direction of attack of diimide,22 which is an electrophilic reagent (eq 3). 23 The similar role of the bent bond was observed in electrophilic additions to bicyclo[3.1.0]hexene (eq 4).…”

Chemical consequences of orbital interactions. II. Ethylene and butadiene bridged polycyclic hydrocarbons containing three- and four-membered rings

“…Similar transformations for the other ethylene bridged compounds, 3, 5 and 6, can be performed to yield cations 25, 26, and 27, respectively. The cationic centers in these systems are, by analogy, not expected to receive substantial hyperconjugative stabilization since the stabilization in the parent olefins of [25][26][27] was dominated by the interaction of a high-lying, filled, antisymmetric ring orbital with the * orbital of the ethylene bridge. Loss of this interaction plus the lack of strong interactions between symmetric orbitals of ring and bridge for the cations is expected to result in little stabilization for 25-27.…”

Application of the Cplex-isoelectronic theory to electrocyclisations, sigmatropic rearrangements, cheletropic reactions and antiaromaticityConsistent with Santilli's hadronic chemistry

“…The activation energy [11] is lower than cyclobutene and the SKIE is small and normal [12], consistent with a concerted process and an alternative reaction mechanism to the ADEP process. The relatively high paramagnetism of bicyclopentene [13] provides evidence that the substrate has single isoelectron character and thus there will be a bias towards an SDSE process [1]. Furthermore the single bond is relatively weak due to strain, rotation restricted due to the cyclic structure and the reaction intramolecular, which favours an SDSE process [1].…”