Keywords: Amides / Hydrodefluorination / Ab initio calculations / Nitrogen heterocycles / Zinc N-Acetylation of polyfluoroarylamines is proposed as a means to remove the amino group blocking effect of their hydrodefluorination by zinc in aqueous ammonia. With pentafluoroacetanilide, the Zn ion specific effect has been demonstrated to be responsible for ortho hydrodefluorination. This regiochemistry is accompanied by the removal of a fluorine atom from the para position, which occurs predominantly in the initial phase of the process in the absence of deliberately added zinc salt. The CuCl 2 additive has been found to accelerate the reaction and to propel it to double defluorination. Quantum chemical calculations suggest a diminished electron affinity of pentafluoroaniline, which is responsible for its inertness in relation to the hydrodefluorination reaction. The pentafluoroaniline radical anion, which essentially has a nonplanar structure, is prone to easy fragmentation to give an aminotetrafluorophenyl radical. For pentafluoroacetani-

Single-crystal Ni-doped gadolinium gallium garnet films were grown for the first time from supercooled Bi2O3–B2O3-based melt solutions by liquid-phase epitaxy. Optical absorption bands due to Ni2+, Ni3+ and Bi3+ ions were observed in those films. Interpretation and tabulation of all absorption bands of nickel ions occupying octahedral and tetrahedral sites in the garnet lattice are presented.

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