Bromination of Halobenzenes¹

Abstract

The ratios of ortho, meta and para isomers produced in the aluminum bromide-catalyzed bromination of fluorobenzerie, chlorobenzene and bromobenzene, and the relative rates of bromination of these halobenzenes with respect t o benzene have been determined in carbon disulfide. Photochemical catalysis gives markedly different results from which it is concluded that the aluminum bromide-catalyzed bromination does not take place by a homolytic mechanism. All analyses were made by infrared spectrophotometry.

α-Fluorinated Ethers, Thioethers, and Amines: Anomerically Biased Species

“…Electron-donors such as alkoxy (aryloxy), alkylthio (arylthio), and dialkylamino groups effectively stabilize adjacent carbenium ions 23 and thus immensely facilitate S N 1 processes. , Consequently, α-fluorinated ethers, thioethers, and amines must be and are sensitive toward Brønsted and Lewis acids. As fluorine can also share nonbonding electrons with a positively charged center, − one might expect the lability to increase with the number of α-fluorine atoms. However, the hydride affinity does not grow monotonically in the series methyl, fluoromethyl, difluoromethyl, and trifluoromethyl cation but diminishes upon introduction of the third fluorine atom .…”