Rearrangement of 3-membered 1,1,2-trifluorobromonium and iodonium ions and comparison of trifluorochloronium to fluorocarbenium ions.
Reactions of chlorine (Cl(2)) with 4-halo-1,1,2-trifluorobut-1-enes (1, 2, or 3) give open-ion intermediates A and E that are in equilibrium. The open-chloronium ions (E) rearrange to a five-membered-ring halonium ion during ionic chlorination of 3 when the number-4 halo-substituent is iodine. Three-membered-ring bromonium and iodonium ions from alkenes 1, 2, or 3 are rather symmetrical and similar in structure. Quantum chemical calculations show that five-membered-ring halonium ion intermediates are 11 to 27 kcal/mol more stable than the three-membered-ring halonium ions or the open-ions A and E. The five-membered-ring intermediates lead to rearranged products. Rearranged products increase as the number-4 halogen (Z) becomes more nucleophilic (Z: Cl < Br < I). Open chloronium ions from ionic chlorination of terminal fluorovinyl alkenes are compared to the open ions generated by protons to similar alkenes.
Shellhamer
Dale F
DF
Department of Chemistry, Point Loma Nazarene University, San Diego, CA 92106-2899, USA. dshellha@pointloma.edu
Davenport
Kevyn J
KJ
Forberg
Heidi K
HK
Herrick
Matthew P
MP
Jones
Rachel N
RN
Rodriguez
Sean J
SJ
Sanabria
Sunamita
S
Trager
Nicole N
NN
Weiss
Ryan J
RJ
Heasley
Victor L
VL
Boatz
Jerry A
JA