Thermal isomerization. 9. The role of cyclopropene in the allene to propyne isomerization. A study of the thermal rearrangements of C3H3D isomers

Chemistry of Energetically Activated Cumulenes—From Allene (H2CCCH2) to Hexapentaene (H2CCCCCCH2)

“…1,2-H shift!propyne (CH 3 CCH). These studies confirmed the proposal of Walsh and co-workers [117][118][119] that the allene-propyne isomerization takes place via the cyclopropene intermediate. The height of the isomerization barrier was found to be 275 kJ mol À1 above the zero-energy level of propyne, which itself lies 3 kJ mol À1 below allene.…”

Reactive intermediates in the interconversions of C3H4 hydrocarbons

“…The triplet has as highest singly occupied molecular orbitals a 2p AO and an in-plane hybrid orbital with the latter slightly lower in energy. [20,2i], thermochemical calculations [21], and a deuterium labelling study using propyne-l-d_l [22], support the gross features of the mechanism in Scheme 2, the picture is complicated by the possible intervention of are than one electronic state of vinylmethylene.…”

Thermal rearrangements of unsaturated and strained organosilanes and their hydrocarbon counterparts

“…and Acetylenes Honjou et al have calculated the potential energy surface for the isomerization of methylacetylene to aliéné(1). They find propenylidene, cyclopropene, and vinylcarbene to be stable intermediates on this surface.Other calculations and experimental work have supported these results(2,5,6,9,11). to organosilanes, we were curious as to the behavior of the analogous hydridosilylacetylenes.Will tjiey undergo rearrangement to silacyclopropenes and silaallenes?…”