Patent GB-774763-A (GB)
Title: Esters of halogenated phenoxyacetic acids and process for the preparation thereof
IPC: C07C59/70
Filed: 1955-09-20
Abstract: The invention comprises compounds of the formula <FORM:0774763/IV(b)/1> where X is halogen and n is an integer from 1 to 5, Y is methyl and m is 0 or 1, R1 and R2 are hydrogen, methyl or ethyl and R3 is hydrogen, an alkyl radical of 1-8 carbon atoms or the residue of an alkylene or polyalkylene glycol the free hydroxy group of which may be etherified with an alkyl group, the alkyl and alkylene groups each being of not more than 8 carbon atoms, for example residues of the formula -CH2CH2-O-CH3, -CH2-CH2-O-CH2-CH3 and <FORM:0774763/IV(b)/2> The compounds are made by esterifying the corresponding phenoxyacetic acid or a functional derivative such as an ester or halide thereof with an a -hydroxycarboxylic acid or an ester thereof of the general formula HO-CH(R2)-COOR3, or by reacting the halide of the phenoxyacetic acid compound with a mono-alkali metal, e.g. sodium, salt of an ester of the a -hydroxycarboxylic acid or with a di-alkali metal salt of the a -hydroxycarboxylic acid. When the product of the esterification reaction is one in which R3 is hydrogen, it can be further esterified with an alkanol or the appropriate glycol or polyglycol compound.  The esterification is suitably carried out in an inert solvent such as toluene, benzene or xylene and in the presence of an esterification catalyst such as p-toluene sulphonic, sulphuric or phosphoric acid.  Water liberated during the esterification reaction is suitably removed by azeotropic distillation.  Examples describe the preparation of 2 : 4 : 5-trichlorophenoxyacetyl-lactic acid and its ethyl and amyl esters, 2 : 4-dichlorophenoxyacetyl lactic acid ethyl ester, 2 : 4 : 5-trichlorophenoxyacetyl glycolic acid butyl ester and 2-methyl-4-chlorophenoxyacetyl-lactic acid amyl ester.  Many other chloro-, bromo-, iodo- and fluoro-phenoxyacetic acids and esters of lactic, glycollic and a -hydroxybutyric acid which may be reacted to form products according to the invention are specified.ALSO:Herbicidal compositions comprise phenoxy acetic acid derivatives of the general formula <FORM:0774763/VI/1> in which X is a halogen and n is an integer from 1 to 5, Y is methyl and m is 0 or 1, R1 and R2 are hydrogen, methyl or ethyl, and R3 is hydrogen, an alkyl group of 1-8 carbon atoms or the residue of an alkylene or polyalkylene glycol, the free hydroxy group of which may be etherified with an alkyl group, the alkyl and alkylene groups each being of not more than 8 carbon atoms, with a carrier.  Specified phenoxyacetic acid derivatives include 2:4:5- trichlorophenoxyacetyl-lactic acid and its ethyl and amyl esters, 2:4-dichlorophenoxyacteyl-lactic acid and ethyl ester, 2:4:5-trichlorophenoxyacetyl-glycolic acid butyl ester and 2-methyl-4-chlorophenoxyacetyl-lactic acid amyl ester.  Many chloro, bromo, iodo and fluoro-phenoxyacetic acids and a-hydroxy-carboxylic acids which may be combined to form active ingredients of the formula I are specified (see Group IV(b)). Suitable herbicidal compositions comprise an aqueous emulsion of 0.1-0.2 per cent of an active ingredient of formula I and from 0.04-0.1 per cent of an emulsifying agent such as naphthalene sulphonate or an aqueous suspension containing 0.1-0.2 per cent of the compound of formula I, 0.02-0.1 per cent of a wetting agent and from 0.1-0.2 per cent of a solid carrier such as kaolin, chalk, peat or sawdust.  The compositions may be solutions of the herbicide in e.g. diesel oil, kerosene, xylene or other herbicidal oils.