Abstraction of Iodine from Aromatic Iodides by Alkyl Radicals:  Steric and Electronic Effects^,

Abstract

Abstraction of the iodine atom from aryl iodides by alkyl radicals takes place in some cases very efficiently despite the unfavorable difference in bond dissociation energies of C-I bonds in alkyl and aryl iodides. The abstraction is most efficient in iodobenzenes, ortho-substituted with bulky groups. The ease of abstraction can be explained by the release of steric strain during the elimination of the iodine atom. The rate of abstraction correlates fairly well with the strain energy, calculated by density functional theory (DFT) and Hartree-Fock (HF) methods as a difference in the total energy of ortho and para isomers. However, besides the steric bulk, the presence of some other functional groups in an ortho substituent also influences the rate. The stabilization of the transition state, resembling a 9-I-2 iodanyl radical, by electron-withdrawing groups seems to explain a positive sign of the Hammett rho value in the radical abstraction of halogen atoms.

Synthesis, Characterization, and Reaction of a Both Inter‐ and Intramolecularly Coordinated Pseudocyclic Iodosylbenzene–Trifluoroacetic Acid Complexes

“…Synthesis of 4‐Bromo‐1‐iodo‐2‐(1‐methoxy‐1‐methylethyl)benzene (9b; Procedure C): Sodium hydride (0.41 g, 10.4 mmol, 1.77 equiv.) was diluted with dry tetrahydrofuran (THF; 7 mL), and 5‐bromo‐2‐iodo‐α,α‐dimethylbenzenemethanol (2.0 g, 5.86 mmol, 1.0 equiv.)…”

Photomediated Controlled Radical Polymerization and Block Copolymerization of Vinylidene Fluoride

“…1 H- and 19 F-NMR confirm the decarboxylation and selective, regiospecific, CX 3 • initiation, i.e., predominant formation of CX 3 –CH 2 –CF 2 –PVDF not CX 3 –CF 2 –CH 2 –PVDF, and the absence of CX 3 COO–PVDF (eq 2′). Moreover, as indicated by the absence of any PVDF–I chain ends, no IDT derived from the potential trapping , of the growing chain with the photolytically unstable , iodanyl (9-I-2) − radicals (e.g., R–I • –Ph or RI • (−Ph–COO−), R = CX 3 –, CX 3 COO–, and PVDF−) or by chain transfer with the in situ generated PhI is occurring. Thus, decarboxylation is faster than addition to VDF, and the cogenerated Ph–I or HOOC–Ph–I are not effective iodine CT agents at 40 °C.…”

Cyclic Haloiodanes: Syntheses, Applications and Fundamental Studies

“…Several groups used the formation of chloroiodanes as a means of purifying the corresponding alcohols. The chloroiodanes can be easily crystallized, then reduced back into the corresponding alcohol with sodium sulfite, [33] hydrogen sulfide [14] or triphenylphosphine [34] …”