Patent GB-898943-A (GB)
Title: Production of carboxyphenyl derivatives of pentavalent phosphorus
IPC: C07F9/30
Filed: 1958-08-29
Abstract: Carboxyphenyl derivatives of pentavalent phosphorus comprising carboxyphenyl phosphonic acids and carboxyphenyl phosphine oxides are obtained by reacting a compound having the formula <FORM:0898943/IV (b)/1> wherein x is 1, 2 or 3, y is 0, 1 or 2, the sum of x and y being equal to 3, and each R is a methyl substituted benzene ring containing from 1 to 3 methyl groups, with molecular oxygen-containing gas at elevated temperature in the liquid phase in an inert organic medium which is liquid at the reaction temperature and in which the starting material is soluble at the reaction temperature and in the presence of a catalyst comprising in conjoint presence bromine and a heavy metal oxidation catalyst. Preferred oxidation temperatures are between about 250 DEG F. and 500 DEG F. and suitable pressures are between atmospheric and 1,500 p.s.i.g. The inert organic medium is preferably a saturated C2-C8 aliphatic monocarboxylic acid, especially acetic acid.  Suitable oxidation catalysts comprise heavy metals having an atomic weight of from about 50 to about 200 and the oxidation catalyst may be in the form of the elemental metal or an oxide, hydroxide, or preferably salt thereof, e.g. a carboxylic acid salt such as cobalt acetate, manganese acetate, cobalt butyrate, manganese linoleate, cobalt naphthenate, manganese naph thenate, manganese benzoate, and manganese toluate. The bromine employed as co-catalyst may be in elemental, combined, or ionic form, e.g. in the form of bromine itself, ammonium-, sodium-, or potassium-bromide, tetrabromoethane, benzyl bromide or ethyl bromide.  Also, bromine-containing salts of the metallic oxidation catalyst may be employed, e.g. manganese-, cobalt- or molybdenum-bromide or mixtures thereof.  The amount of catalyst is preferably between 0.01% and 2% by weight of the oxidizable compound and the bromine-containing compound is generally employed in an amount sufficient to provide from 0.1 to 10 atoms of bromine per atom of metal oxidation catalyst.  The oxidant may be pure oxygen, air, or air or oxygen diluted with an inert gas, e.g. nitrogen or carbon dioxide, and the process may be carried out p  batchwise intermittently or continuously.  Examples are given for the oxidation of (1) tri-m-tolyl phosphine oxide to tri-m-carboxyphenyl phosphine oxide and (2) and (3) of bis-(2,5-dimethylphenyl) phosphonic acid to bis-(2-methyl-5-carboxyphenyl) phosphonic acid and to 2 - methyl - 21, 5, 51 - tri - carboxy - diphenyl phosphonic acid, respectively. The products are useful as plasticisers for various plastics, in the production of alkyd resins and fibreforming polymers and for imparting flameproofing characteristics to thermoplastic resinous compositions.  Tri-m-tolyphosphine oxide is obtained by adding a solution of phosphorus oxychloride in ether to m-tolyl magnesium bromide, maintaining the temperature at 30 DEG C.-35 DEG C. and then decomposing the mixture with a solution of concentrated hydrochloric acid in water.  Bis-(2,5-dimethylphenyl) phosphonic acid is obtained by refluxing a mixture of p-xylene, PCl3 and anhydrous AlCl3, stripping to remove excess PCl3, diluting with s-tetrachloroethane, cooling to -5 DEG C. and saturating with chlorine at 0 DEG C. Alcohol is then added and the evolved HCl removed and the mixture is then poured on to crushed ice and concentrated HCl added.  The tetrachloroethane layer is separated and the aqueous layer extracted with 5% HCl and then with water and the extract distilled to yield diethyl 2,5-dimethylbenzene phosphonate as distillate and ethyl bis-(2,5-dimethylphenyl) phosphonate as residue.  The latter is then treated with concentrated hydrochloric acid to form the corresponding acid -bis-(2,5-dimethylphenyl) phosphonic acid.  Specification 763,982 also is referred to.