Abstract: 1 A process for producing a purified organophosphorus alkyl ester compound in which the reaction mixture obtained by reacting a dichlorophosphine derivative with (meth)acrylic acid is esterified with a lower monool, and the resulting reaction mixture is neutralized with an alkali metal hydroxide or alkaline earth metal hydroxide either in a solid form or in the form of an aqueous solution and purified; 2 a process for producing a purified organophosphorus hydroxyalkyl ester compound or an alkylene glycol solution thereof which comprises subjecting the purified organophosphorus alkyl ester compound obtained by process 1 to transesterification with an alkylene glycol; 3 a reactive flame retardant comprising the purified organophosphorus alkyl ester compound obtained by process 1; and 4 a reactive flame retardant comprising the purified organophosphorus hydroxyalkyl ester compound or alkylene glycol solution obtained by process 2.

Abstract: A phosphine derivative of the following general formula ( I ): ##STR1## (wherein R.sup.1 is an alkyl group having 1 to 18 carbon atoms or an aryl group having 6 to 18 carbon atoms, and the aryl group may have an alkyl group having 1 to 18 carbon atoms or an alkenyl group having 2 to 18 carbon atoms) is reacted with acrylic acid or methacrylic acid in the presence of a catalyst selected from the group consisting of an organic peroxide and an azo-compound, and the resulting reaction product is hydrolyzed with water, thereby to obtain a phosphinyl-carboxylic acid derivative of the following general formula (III): ##STR2## (wherein R.sup.1 is as defined above, and R.sup.2 is a hydrogen atom or a methyl group). Based on the reaction above-mentioned, ester of free acid and a cyclic acid anhydride can also be obtained. Accordingly, the target compound can be obtained at a relatively low reaction temperature in a short period of time with high yield.

Abstract: Aromatic phosphorus-chlorine compounds, especially diphenylphosphinyl chloride (C.sub.6 H.sub.5).sub.2 P(O)Cl, phenylphosphonyl dichloride C.sub.6 H.sub.5 P(O)Cl.sub.2, dichlorophenylphosphine C.sub.6 H.sub.5 PCl.sub.2 and chlorodiphenylphosphine (C.sub.6 H.sub.5).sub.2 PCl, and the corresponding sulfur analogs, are obtained by reaction of aromatic phosphorus compounds, which contain oxygen or sulfur, of the formula I ##STR1## in which X=O or S, and m=1, 2 or 3, with phosphorus-chlorine compounds of the formula II(C.sub.6 H.sub.5).sub.3-n P Cl.sub.n (II)in which n=1, 2 or 3, at temperatures between about 330.degree. and 700.degree. C. Preferred starting materials are triphenylphosphine oxide (C.sub.6 H.sub.5).sub.3 PO and phosphorus trichloride PCl.sub.3.The reaction products are mainly intermediates in a variety of special areas, such as the pharmaceuticals, plant-protection, dye and polymer sectors.