PREPARATION OF MONOHALOACETYL HALIDES

1374323 Monohaloacyl halides MONSANTO CO 29 Sept 1972 [26 Oct 1971 30 Sept 1971 (3) 31 July 1972 (3) 4 Aug 1972] 45053/72 Heading C2C Monohaloacyl halides are prepared by reacting an optionally substituted ketene with Cl 2 , Br 2 , I 2 or an interhalogen compound thereof in the presence of, as liquid solvent, one or more of (a) a cyclic carbonate of formula wherein R, R1, R2, R3, R4 and R5 are each hydrogen, halogen, methyl, chloromethyl, phenyl or ethyl and n is 0 or 1; (b) an alkoxyalkyl ester of formula wherein R6 and R8 are each C 1-5 alkyl radicals and R7 is C 1-5 alkylene, the total number of carbon atoms in R6, R7 and B8 being 3 to 10 inclusive; (c) an ester of formula wherein R9 is alkyl of at least 2 carbon atoms (e.g. 2 to 7) and R10 is C 1-4 alkyl; or (d) a glycol diester of formula wherein R20 and R11 are each C 1-4 alkyl, R12 to R19 are each hydrogen, methyl or ethyl, with not more than 3 of R12 to R19 being other than hydrogen and a and b are each 0 or 1. The ketene and halogen or interhalogen are preferably introduced concurrently into the solvent using a molar ratio of halogen (or interhalogen) to ketene of between 1 : 1 and 1À3 : 1. The required cyclic carbonate may be formed in situ from the corresponding unsaturated carbonate by addition of the halogenating agent. The process may be carried out continuously or batch-wise. Examples describe the halogenation of ketene, methyl ketene and phenyl ketene with Cl 2 and Br 2 to produce the corresponding monohaloacyl halides. Acyl halides and dihaloacyl halides are obtained as by-products. Exemplified and specified solvents are: ethylene carbonate, tetrachloroethylene carbonate, 1,2- and 1,3- butylene carbonates, chloromethylethylene carbonate, phenylethylene carbonate, 1,2- and 1,3-propylene carbonates, 2,2-dimethyl-1,3-propylene carbonate, 1,2-diethyl-1,3-propylene carbonate, 1,2-dimethylethylene carbonate, 1,2- diethylethylene carbonate, all the solvents falling into category (b), the methyl, ethyl, propyl and butyl esters of propionic, butyric, valeric, caproic, enanthylic and caprylic acids and the acetates, propionates, butyrates and valerates of ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, 1,2- butylene glycol, 1,3-butylene glycol and isobutylene glycol. Comparative examples use as solvents: methyl, ethyl, butyl and hexyl acetates, carbon tetrachloride, 1,2-dichloroethylene, acetonitrile, benzonitrile and nitromethane.