Patent GB-833594-A (GB)
Title: Chlorination of alkyl esters of aromatic carboxylic acids
IPC: A01N37/10
Filed: 1957-10-15
Abstract: Alkyl esters of aromatic or chlorine-substituted aromatic mono- or polycarboxylic acids, free from other nuclear substituents and having 1-5 carbon atoms in each alkyl group are converted into chloroalkyl esters by passing gaseous chlorine into them while they are maintained in the liquid phase under substantially anhydrous conditions at 0-100 DEG  C., and in the presence of actinic radiation.  When the reaction is carried out at relatively low temperature, e.g. 0-40 DEG  C., additive chlorination of the aromatic nucleus takes place as a competing reaction and an alkyl ester of a hexachlorocyclohexane carboxylic acid may also be obtained.  The actinic radiation may be sunlight, light emitted from fluorescent or incandescent lamps, ultra-violet rays, X-rays, or waves of even shorter length.  For continuous operation submersion type light sources may be immersed in a reactor and the chlorine and alkyl ester may be passed into the reactor in countercurrent flow to one another, and the chloroalkyl ester product is continuously removed from the reaction zone.  Many reactants and products are specified (see Group IV (b)).  Products specially mentioned or described include alpha-chloroalkyl phthalates such as chloromethyl methyl phthalate, chloromethyl benzoate, alpha-chloroethyl benzoate, monochloro butyl benzoate, the half chloromethyl ester half acid chloride of isophthalic acid, dichloromethyl 3,4-dichlorobenzoate, and methyl ester of 1,2,3,4,5,6 - hexachloro - cyclohexane monocarboxylic acid.ALSO:The invention comprises alpha-chloroalkyl alkyl phthalates and alkyl 1,2,3,4,5,6-hexachlorocyclohexane monocarboxylates in which the alkyl group contains 1-5 carbon atoms, and a process for preparing chloroalkyl esters of aromatic mono or polycarboxylic acids which may be substituted in the nucleus with chlorine by passing gaseous chlorine into a C1-C5 alkyl ester of the acid (which must be free from nuclear substituents other than chlorine) in the liquid phase under substantially anhydrous conditions at 0-100 DEG  C. in the presence of actinic radiation. The products of the reaction are alkyl esters of the additively chlorinated aromatic carboxylic acid, and the chloroalkyl ester of the non-chlorinated acid.  Suitable starting materials are methyl, ethyl, propyl, butyl and amyl benzoates, methyl 1- and 2-naphthoates, isobutyl 1-naphthoate, the methyl esters of diphenyl 2-, 3- and 4-carboxylic acids, methyl - 9 - phenanthioate, methyl - 9 - anthroate, dimethyl phthalate, dimethyl isophthalate, dimethyl terephthalate, diethyl phthalate, methyl amyl phthalate, ethyl amyl phthalate, methyl isobutyl terephthalate, dimethyl diphenate, dimethyl 4,41-diphenyldicarboxylate, dimethyl 1,8-naphthalenedicarboxylate, tetramethyl prehnitate, dimethyl 9,10-anthracenedicarboxylate, methyl o-chlorobenzoate, methyl p-chlorobenzoate, methyl 2,4-dichlorobenzoate, ethyl 2,4,5-trichlorobenzoate, amyl parachlorobenzoate, methyl 4-chloro-1-naphthoate, ethyl-5 - chloro - 2 - naphthoate, methyl 2 - chloro-4 - diphenylcarboxylate, methyl 10 - chloro - 9 - anthroate, dimethyl 4 - chlorophthalate, dimethyl tetrachlorophthalate, and dimethyl-4-chloronaphthalate.  Among specified compounds prepared according to the process of the invention are alpha - beta - dichloroethyl benzoate, alpha - chlorobutyl benzoate, alphachloroethyl - 2 - naphthoate, alpha - beta - chloroethyl 1 - naphthoate, chloromethyl 2,4,5 - trichlorobenzoate, dichloromethyl 3,5-dichlorobenzoate, trichloroethyl para - chlorobenzoate, chlorobutyl 2,4 - dichlorobenzoate, chloromethyl 5 - chloro - 1 - naphthoate, chloroethyl 10 - chloro - 9 - anthroate, chloromethyl methyl phthalate, alpha-chloroethyl ethyl phthalate, alpha-chloro-n-propyl n-propyl phthalate, alpha-chlorobutyl butyl phthalate, alpha-chloroethyl amyl phthalate, chloromethyl ethylphthalate, chloromethyl methyl diphenate, bis - (chloromethyl) - 9,10 - anthracenedicarboxylate.  The process of the invention is preferably carried out at 15-50 DEG  C. and the aromatic ester preferably dissolved or suspended in an anhydrous inert solvent or diluent.  Suitable solvents are, e.g. tetrachloroethane, carbon tetrachloride, trichloromonofluoromethane, carbon tetrachloride, trichloromonofluoromethane, and dichlorodifluoromethane. Suitable sources of actinic radiation are sunlight, light emitted by fluorescent or incandescent lamps, ulta-violet rays and X-rays.  It is preferred to pass the chlorine through the reaction mixture, at such a rate that a portion of the chlorine passes through the chlorinating mass unreacted to remove hydrogen chloride from the reaction mixture.  Alternatively the chlorine may be introduced into the reaction mixture at such a rate that it is substantially completely absorbed, the hydrogen chloride formed being removed either by passing an inert gas, e.g. nitrogen through the mixture or by applying reduced pressure to the system. The chlorination is preferably continued until the gain in weight of the charge is between 95 and 110% of the amount theoretically required for conversion of the alkyl ester charged to the desired chlorinated ester.  The process may be carried out batchwise or continuously. Examples are given of the preparation of chloromethyl benzoate; and methyl 1,2,3,4,5,6 - hexachloro - cyclohexanecarboxylate; a -chloroethyl benzoate; a mixture of monochlorobutyl benzoates, a mixture of mono- and dichlorobutyl benzoates, chloromethyl methyl phthalate, bis-(chloromethyl) isophthalate which is not isolated and the halfchloromethyl ester, half-acid chloride of isophthalic acid, dichloromethyl 3,4-dichlorobenzoate, a mixture of polychloroethyl orthobenzoates containing alpha, beta dichloro substituted esters, and alpha chloroethyl 3,4-dichlorobenzoate.ALSO:Polyvinyl chloride compositions contain as plasticizer an alpha-chloroalkyl alkyl ester of phthalic acid in which each alkyl group contains 1-5 carbon atoms (see Group IV (b)). Chloromethyl methyl phthalate may be mixed with polyvinyl chloride in an amount of 10-30% by weight of the weight of the polymer.  Chloroethyl ethyl, chloro-n-propyl n-propyl, chlorobutyl butyl, chloroethyl amyl, chloroamyl amyl, and other similar esters of phthalic acid are specified.ALSO:Chloroalkyl esters of aromatic or chlorine-substituted aromatic mono- or polycarboxylic acids and alkyl esters of hexachloro cyclohexane carboxylic acids in which each alkyl group contains 1-5 carbon atoms (see Group IV (b)) may be used as biological toxicants.  Specially mentioned are the alpha-chloroalkyl alkyl esters of phthalic acid such as chloromethyl methyl, chloroethyl ethyl, chloro-n-propyl propyl, chloroethyl amyl, chloroamyl amyl, and similar esters of phthalic acid.  Chloromethyl methyl phthalate incorporated in agar at a strength of 1 in 10,000 inhibits the growth of Aspergillus niger.  Specified cyclohexane compounds are the methyl, ethyl, isopropyl, butyl, and amyl esters of 1, 2, 3, 4, 5,6 - hexachlorocyclohexane monocarboxylic acid. These compounds may be used as insecticides, fungicides, and herbicides. In an example, the methyl ester is introduced at a concentration of 10 parts per million into an aqueous suspension of yellow fever mosquito larvae and a complete killing is obtained.  The methyl ester added to a dextrose-agar preparation at a concentration of 1 part 1000 inhibits Aspergillus niger.  It may be used as a spray of 0.5% strength and applied to foliage so as to kill young broadleaf plants such as clover while leaving grasses unaffected.  It may be applied as a pre-emergent spray on to soil containing seeds of broad and narrow leaf plants so as to injure the emergent grasses but allow the broadleaf plants, e.g. sugar beet, to emerge as healthy seedlings.