Patent GB-581900-A (GB)
Title: Improvements in or relating to the manufacture of carboxylic acids
IPC: C07C51/093
Filed: 1943-04-12
Abstract: Carboxylic acids are prepared from a compound containing a trichlormethyl group attached to an organic radical through a hydrogen-bearing carbon atom or a monodehydrochlorination product thereof by hydrolysing with water in the presence of sulphuric acid maintained at a concentration of 85-99 per cent by weight. The trichlormethyl compound and an equal weight of concentrated sulphuric acid may be heated to about 95 DEG  C. and a slight excess of water over the theoretical two molecular equivalents then added, preferably diluted with sulphuric acid, at a rate calculated to maintain the necessary concentration.  The amount of acid is widely variable, 1-5 molecular equivalents being preferred.  Temperature may be atmospheric or above, preferably about 100-125 DEG  C.  With a large excess of acid initially added, further addition of water may be unnecessary.  The carboxylic acid may be isolated by precipitation, solvent extraction, steam distillation or as an ester by diluting and heating with a suitable alcohol.  Instead of the trichlormethyl compound, the dichlorolefin obtained by dehydrohalogenation thereof, for example as described in Specification 581,901 may be used.  The trichlormethyl compounds, which can be prepared as described in Specification 581,899, may be represented by the formula <FORM:0581900/IV/1> where X is H or halogen, R1 is H or a hydrocarbon radical, and R is a divalent hydrocarbon radical, preferably an aliphatic radical of 3-12 carbon atoms, or an aliphatic radical having a terminal substitutent group inert to the hydrolysis conditions such as chlorine, carboxyl or amino.  Other substituent groups may, however, be present, for example a trichlormethyl group attached to a hydrogen-bearing carbon atom, an ester or amide group which would be hydrolysed, and an alcohol group which would be sulphated.  The carbon chain of R may contain one or more other atoms such as sulphur linked as mono- or di-sulphide or sulphone, oxygen as ether, and nitrogen as amine.  R may also be an aryl or aryl-aliphatic radical when sulphonation may take place.  Examples of these various types of compound are given.  The carboxylic acid products are useful as intermediates and for preparing dibasic acids. Thus, 5-chlorvaleric acid gives d -valerolactone by heating the sodium salt in water or methanol, this being polymerizable with, for example, diamine dibasic acid salts to form polyester amides.  The w-chlor-acids can be converted to w-cyano-acids and thence to a -a -dicarboxylic acids, used in preparing resins, plasticisers and nylon.  In examples: (1) water and sulphuric acid are slowly added below the surface of a mixture of 1,1,1,5-tetrachlorpentane and sulphuric acid at 90-95 DEG  C. to yield 5-chlorvaleric acid which is separated by cooling and diluting the mixture and extracting with carbon tetrachloride; (2) bis-(5,5,5-trichlorpentano) sulphide made by the action of sodium sulphide on 1,1,1,5-tetrachlorpentane similarly hydrolyses to bis-(4-carboxybutane) sulphide; (3) 1,1,5-trichlorpentene-1, made by heating 1,1,1,5-tetrachlorpentane with zinc chloride and acetic acid as in Specification 581,901, is hydrolysed and the acid isolated as methyl 5-chlorvalerate; (4) 1,1,1-trichlornonane is heated with 96 per cent sulphuric acid to give pelargonic acid.