Patent GB-799435-A (GB)
Title: Improvements in or relating to phenoxy-acetic acids having herbicidal properties
IPC: C07C59/70
Filed: 1955-10-21
Abstract: The invention comprises the chlorophenoxyacetic acids or metal salts or esters thereof obtained by subjecting a benzene hexachloride containing mixture called "delta paste" to dehydrochlorination and hydrolysis to form a product containing chloro-substituted phenols and reacting the phenols with a compound of the formula XnCH2-n-COOR, wherein n is 1, 2 or 3, X is a halogen and R represents hydrogen, a metal or an alkyl or aryl group.  By "delta paste" is meant the material containing the delta isomer of benzene hexachloride and oils which is obtained by removing as far as possible the alpha, beta and gamma isomers from a benzene hexachloride isomer mixture resulting from the total addition chlorination of benzene, and includes benzene hexachloride isomer mixtures containing the delta isomer and oils in which mixtures the content of the delta isomer and oils constitutes a major proportion, e.g. a mixture containing 16.9 per cent by weight of the gamma isomer, 70 per cent by weight of the delta isomer and oils and the balance a mixture of other unremoved benzene hexachloride isomers, solvent and solvent impurities.  The group R preferably represents an alkali metal such as sodium or potassium, a substituted or unsubstituted alkyl group such as the methyl or ethyl group, or a substituted or unsubstituted aryl group such as the phenyl or naphthyl group.  A "delta paste" containing about 70 per cent of the delta isomer and oils yields no less than 6 chlorobenzenes on dehydrochlorination, i.e. 1,2 - dichlorobenzene and 1,2,3 -, 1,2,4 - and 1,3,5 - trichlorobenzenes and 1,2,3,4 - and 1,2,4,5 - tetrachlorobenzenes.  The dehydrochlorination may be accomplished in an aqueous or alcoholic medium in the presence of one or more alkali metal hydroxides such as sodium or potassium hydroxide, preferably using an excess of alkali metal hydroxide, e.g. the dehydrochlorination may be effected in methanol using a 10 to 15 per cent excess of sodium hydroxide.  The dehydrochlorination may be carried out as an anhydrous operation using metal halides such as zinc and/or aluminium chlorides, nitrogen bases such as trialkylamines, dialkylamines, alkylamines and their hydrochloride salts as dehydrochlorinating agents.  The dehydrochlorination step may be carried out at an elevated temperature and/or pressure.  The hydrolysis step may be carried out using an aqueous or alcoholic medium in the presence of one or more alkali metal hydroxides such as sodium or potassium hydroxide, or an alkaline earth metal hydroxide such as is produced using calcium, barium or strontium oxide.  An elevated temperature and pressure may be used for the hydrolysis step.  The hydrolysis step may be carried out as a continuation of the dehydrochlorination step by adding an additional quantity of alkali metal hydroxide.  Suitable compounds of the general formula XnCH3-n-COOR wherein n, X and R have the above significance, which may be used are halogenated acetic acids, e.g. mono-, di- and tri - chloroacetic acids, bromoethyl acetate, chloroethyl acetate, bromomethyl acetate, chloromethyl acetate, bromobenzyl acetate and chlorobenzyl acetate.  In the examples a delta paste consisting of 70 per cent of the delta isomer of benzene hexachloride plus oils and 16.9 per cent of the gamma isomer of benzene hexachloride is dehydrochlorinated and then hydrolysed with sodium hydroxide to form a polychlorophenol product and is then reacted with (a) monochloroacetic acid to form chlorophenoxyacetic acids having the empirical formula C8H5.6Cl2.4O3.0; and (b) bromoethylacetate to form chlorophenoxyacetates having the empirical formula C8H5.2Cl2.3O3.1.ALSO:A herbicidal composition comprises the chlorophenoxyacetic acids and salts and esters thereof obtained by subjecting a benzene hexachloride containing mixture called "delta paste" to dehydrochlorination and hydrolysis to form a product containing chloro-substituted phenols and reacting the phenols with a halogenated acetic acid or a salt or ester thereof of the formula XnCH3-n-COOR, wherein n is 1, 2 or 3, X is a halogen and R represents hydrogen, a metal or a substituted or unsubstituted alkyl or aryl group (see Group IV (b)).  By "delta paste" is meant the material containing the delta isomer of benzene hexachloride and oils which is obtained by removing as far as possible the alpha, beta and gamma isomer of benzene hexachloride from a benzene hexochloride mixture resulting from the total addition and chlorination of benzene, and includes benzene hexachloride isomer mixtures containing the delta isomer and oils in which mixtures the content of the delta isomer and oils constitutes a major proportion, e.g. a mixture containing 16.9 per cent by weight of the gamma isomer, 70 per cent by weight of the delta isomer and oils, and the balance a mixture of other unremoved benzene hexachloride isomers solvent and solvent impurities.  The composition may include a carrier and may be employed in the form of liquids, emulsions, slurries, solutions or powders such as granules or pellets.  Suitable inert fillers are pyrophyllite, diatomaceous earth, talc, clay, sand, dry soil, kaolin, chalk, gypsum or other inorganic or organic materials including active ingredients such as fertilizers, insecticides and/or fungicides.  Liquid drench or spray materials may be formulated using various solvents, diluents or extenders such as water, aromatic and aliphatic organic liquids including acetone, benzene and/or various alcohols, ethers, ketones and petroleum fractions.  Wetting agents may also be incorporated in the mixtures, suitable wetting agents being of the following types: organic sulphonate; quaternary ammonium compound; polyoxyethylated vegetable oil, fatty alcohol or base formed by condensing propylene oxide with propylene glycol; modified phthalic glycerol alkyd resin; alkyl phenoxypolyoxyethylene ethanol; polyoxyethylene sorbitan mono- and tri-oleate; polyether alcohol; polyhydric alcohol ester; polyethylene glycol t-dodecyl thioether;, and sorbitan mono-palmitate.