DE600706C - Process for the preparation of aromatic compounds fluorinated in the core - Google Patents

Description

Process for the production of aromatic compounds which are fluorinated in the core It is well known that iodobenzene can be easily produced by using a diazonium compound cooked in the presence of potassium iodide. With elimination of nitrogen occurs the iodine in the nucleus, even if chlorine ions are present in the solution. This reaction cannot be extrapolated to fluorination without further ado. So is the yield in the case of decomposition of the diazonium fluoride in aqueous solution .only about 50 ° 1 °, too when working in the presence of excess hydrofluoric acid. As an undesirable Phenol is a by-product.

To improve the yield, it has been successfully proposed to first isolate the diazonium borofluoride from the diazonium salt solution of the amine in question by a known method and to convert this intermediate product, which is stable in itself, into the desired nuclear fluorinated product by heating with elimination of nitrogen and boron trifluoride (B. 6o [1927 ) S. 11.96 to iigo). However, in its first stage of isolation and drying of the intermediate product, this process is associated with technical difficulties and sensitive losses.

It has been found that the reaction can be carried out with very good yields when placed in a medium of anhydrous or nearly anhydrous hydrogen fluoride performs. This reaction benefits from the fact that many aromatic amines are in excess Are readily soluble in hydrogen fluoride. When diazotizing such a solution of amine in hydrogen fluoride is expediently proceeded in such a way that one does not use dissolved Nitrite, but with solid sodium nitrite or nitrous gases and works with it Excludes water as much as possible.

After the decomposition of the diazonium fluoride has ended, the resulting fluorine compound separated from hydrogen fluoride, z. B. by distillation, or if the resulting fluorine compound is insoluble in hydrogen fluoride, by Decantation. The hydrogen fluoride is rectified and fed back into the reaction. Examples i. In an iron container equipped with a stirrer and cooling system, Soo g of aniline are presented and 100 g of hydrogen fluoride are introduced with good cooling. This is followed by .I30 g of dry sodium nitrite over the course of about one hour. The temperature should be kept at about 5`. After the diazotization, the reaction mixture becomes warmed to 3o to 10 °. Nitrogen escapes in a calm stream, its speed can be easily and safely regulated by heating or cooling. The gas will passed through a reflux condenser in order to avoid losses of fluorobenzene. What remains is a mixture of fluorobenzene, hydrogen fluoride and sodium fluoride, which arose from the sodium nitrite. Distillation turns it into.:. 1.5o g fluorobenzene isolated, corresponding to a yield of 87 loo.

From 100 g hydrogen fluoride, 500 g m-toluidine and 400 g sodium nitrite obtained in the manner described in Example i m-Fluorotolliol, which is from the excess hydrogen fluoride is separated by decanting. Yield 4.-eo g, corresponding to 82% of theory.

Claims (1)

PATENT CLAIM: 'Process for the production of aromatic, essentially fluorinated Compounds from the corresponding amines via the diazonium compounds, thereby characterized in that the diazotization and decomposition in the presence of excess, anhydrous or nearly anhydrous hydrogen fluoride.