GB763992A - Dicarboxyphenylphosphonic acid - Google Patents

Abstract

o-Dicarboxyphenylphosphonic acid and salts thereof are prepared in two stages; (1) polychloro derivatives of a compound of formula <FORM:0763992/IV(b)/1> are prepared by chlorination with elemental chlorine at 100-200 DEG C. until at least one atom of chlorine is introduced into each methyl group, and (2) the product of the first step is simultaneously hydrolysed and oxidized by treatment with an alkaline solution of a watersoluble permanganate to give a compound of formula <FORM:0763992/IV(b)/2> wherein M1-M4 are the same or different cations. The chlorination is conducted, preferably in the presence of ultra-violet light, until 4 or 5 chlorine atoms have been introduced into the methyl groups. For the oxidation and hydrolysis step, potassium, sodium or calcium permanganates and potassium or sodium hydroxides are specified. The potassium compounds are preferred, and give a solution of the tetra-potassium salt, from which manganese dioxide is separated by filtration. The monopotassium salt is precipitated from the solution by addition of mineral acid. The free acid and other salts may be prepared by normal methods. The salts may be derived from sodium, magnesium, calcium, barium, aluminium, iron, zinc, ammonia, amines or quaternary bases. The compounds are used as intermediates in the preparation of organic colouring matters. An example illustrates the invention. Phosphonic dichloride of o-xylene is prepared by reacting o-xylene with hexagonal phosphoric anhydride, the product being either hydrolysed to the phosphonic acid and chlorinated with phosphorus pentachloride or treated directly with phosphorus pentachloride. Specification 737,036 is referred to.