Aromatic Fluorine Compounds and the Determination of their Fluorine Content.

Abstract

The fluorobenzoyl chlorides, FC6H4COCl described below were prepared from SOCl2 and the resp. fluorobenzoic acids. The chlorides are highly refractive, colorless liquids with an odor resembling that of BzCl; they can be distilled without decomp. The o-, m- and p-compds. m. 4°, -30° and 9°; b. 204°, 189° and 191-2° (cor.), resp. When treated with MeOH they give methyl o-, m- and p-fluorobenzoates, m. -20°, -10° and 4.5°; b. 207°, 194-5° and 197° (cor.), resp. Prolonged shaking with aq. NH3 converts the esters into the resp. fluorobenzamides, FC6H4CONH2, which are also formed by adding the chlorides to conc. aq. NH3, at 0°; o-compd., long, white needles from H2O, m. 114°; m-compd., white plates from H2O, m. 128-9°; p-compd., white needles from H2O, m. 153°. The determination of F in aliphatic compds. and also in the side chains of aromatic derivs. offers no difficulty, but when the F is linked to an aromatic nucleus it is necessary to decomp. the substance at 1000°, otherwise some F compd. will volatilize and will escape. This can be accomplished by mixing the substance with CaO and heating the mixture, in the ordinary manner, in a Ni tube, 40 X 4-5 cm. One end of the tube is closed by means of a Ag scraper. The tube is supported with the open end slightly elevated and the heating is commenced at this end and continued during 2 hrs., at a yellow heat. The product is treated as usual and the F weighed as CaF2. A single tube will serve for at least 12 determinations. All the compds. described above were prepared in glass vessels. [on SciFinder(R)]