UV-assisted modification and removal mechanism of a fluorocarbon polymer film on low-k dielectric trench structure.

In this study, we report the first chemical characterization of a plasma-deposited model fluoropolymer on low-k dielectric nanostructure and its decomposition in UV/O2 conditions. Carbonyl incorporation and progressive removal of fluorocarbon fragments from the polymer were observed with increasing UV (≥230 nm) irradiation under atmospheric conditions. A significant material loss was achieved after 300 s of UV treatment and a subsequent wet clean completely removed the initially insoluble fluoropolymer from the patterned nanostructures. A synergistic mechanism of UV light absorption by carbonyl chromophore and oxygen incorporation is proposed to account for the observed photodegradation of the fluoropolymer.

Lithium diisopropylamide solvated by hexamethylphosphoramide: substrate-dependent mechanisms for dehydrobrominations.

Lithium diisopropylamide-mediated dehydrobrominations of exo-2-bromonorbornane, 1-bromocyclooctene, and cis-4-bromo-tert-butylcyclohexane were studied in THF solutions and THF solutions with added hexamethylphosphoramide (HMPA). Rate studies reveal a diverse array of mechanisms based on mono-, di-, and trisolvated monomers as well as triple ions. The results are contrasted with analogous eliminations in THF in the absence of HMPA.

Lithium diisopropylamide-mediated ortholithiation and anionic fries rearrangement of aryl carbamates: role of aggregates and mixed aggregates.

Structural and mechanistic studies of the lithium diisopropylamide (LDA)-mediated anionic Fries rearrangements of aryl carbamates are described. Substituents at the meta position of the arene (H, OMe, F) and the dialkylamino moiety of the carbamate (Me(2)N, Et(2)N, and i-Pr(2)N) markedly influence the relative rates of ortholithiation and subsequent Fries rearrangement. Structural studies using (6)Li and (15)N NMR spectroscopies on samples derived from [(6)Li,(15)N]LDA reveal an LDA dimer, LDA dimer-arene complexes, an aryllithium monomer, LDA-aryllithium mixed dimers, an LDA-lithium phenolate mixed dimer, and homoaggregated lithium phenolates. The highly insoluble phenolate was characterized as a dimer by X-ray crystallography. Rate studies show monomer- and dimer-based ortholithiations as well as monomer- and mixed dimer-based Fries rearrangements. Density functional theory computational studies probe experimentally elusive structural and mechanistic details.