Intramolecular Hydrogen Atom Transfer Reactions of ω-Formylalkyl Radicals in Vapor and Liquid Phases

Article abstract of DOI:10.1021/jo00173a034

A series of ω-formyl- (-CHO and -CDO) -n-butyl, n-pentyl, and n-hexyl radicals (4) has been generated in vapor and solution phases.In the vapor phase, intramolecular aldehyde H- (or D-) atom transfer is a facile process proceeding through 6- or 7-membered transition states.In solution phase, intramolecular aldehydic H-atom transfer occurs to an extent of 74percent via a 6-membered transition state but to only 29percent or 38percent via 7- or 8-membered transition states, respectively.Indirect evidence from both vapor- and solution-phase experiments indicates that intramolecular α-H atom abstraction in ω-formyl radicals (4) occurs to about 10percent in competition with aldehydic H-atom abstraction via 6- and 7-membered transition states but not at all via a 5-membered transition state.