Photochemistry of Alkyl Halides. 11. Competing Reaction via Carbene and Carbocationic Intermediates

Article abstract of DOI:10.1021/jo00183a019

Isotopic analysis of the unsaturated products 6 and 15 resulting from irradiation of the labeled iodides 1-1,1-d2, 1-2,2-d2, and 13-1-d has revealed that they are formed substantially, but not exclusively, via α elimination.The unsaturated products thus arise via competing pathways involving carbene intermediates as well as the previously recognized radical and carbocationic intermediates.Irradiation of iodide 22 in methanol-d afforded ether 23 with partial incorporation of deuterium, but the accompanying ether 24 was formed with no detectable incorporation.Thus, ether 23 is formed via competing pathways involving the carbene 28 and the carbocation 25, whereas ether 24 is formed exclusively via the carbocationic pathway.A mechanism involving formation of the carbene intermediates via either α-hydrogen atom or α-proton transfer within the previously proposed intervening radical and ion pairs is suggested.One iodide studied, 17-2-d, exhibited no detectable α elimination.