A. Diethyl α,δ-dibromoadipate. In a 3-l. three-necked flask (Note 1) fitted with a reflux condenser, a dropping funnel, and a mechanical stirrer are placed 1 kg. (6.85 moles) of adipic acid and 2 kg. (1220 ml., 16.8 moles) of thionyl chloride (Note 2) and (Note 3). The mixture is stirred and heated gently on the steam bath until solution is effected, and the evolution of hydrogen chloride (Note 4) ceases after about 3 hours. The excess thionyl chloride is distilled by heating on a steam bath, the last portion of the reagent being taken off under reduced pressure.

To the acid chloride, mechanically stirred and heated on the steam bath, is added 2.5 kg. (805 ml., 15.6 moles) of dry bromine (p. 124) as rapidly as it will react (Note 5). The addition requires about 12 hours. The contents of the flask are stirred and heated an additional 2 hours, transferred to a dropping funnel (Note 6), and added in a thin stream to 5 l. of absolute ethanol, which has previously been placed in a 12-l. flask provided with a stopper carrying an efficient reflux condenser, a separatory funnel, and a mechanical stirrer. The resulting vigorous reaction is controlled by external cooling. After the dibromoacid chloride has been added, the reaction mixture is allowed to stand at room temperature overnight and is then poured into 5 l. of cold water. The top ethanolic aqueous layer is decanted and extracted once with 8 l. of ether. The oily bottom layer is dissolved in the ether extract and washed first with 1 l. of a 2% sodium bisulfite solution, then with two 1-l. portions of 3% sodium carbonate solution, and finally with several portions of water. The ether solution is dried over 175 g. of potassium carbonate; the solvent is distilled on the steam bath. The yield of residual ester (Note 7) amounts to 2260–2400 g. (91–97%).

B. Muconic acid. To a solution of 3 kg. of potassium hydroxide and 5 l. of methanol (Note 8) in a 12-l. flask, equipped as described above, is added in a thin stream from a separatory funnel (Note 6), and with stirring, 1130 g. (3.14 moles) of diethyl α,δ-dibromoadipate. The ester is heated on the steam bath to nearly 100° before it is added. The addition is so regulated as to permit rather vigorous refluxing and requires 45 minutes. Heating on the steam bath and stirring are continued an additional 2 hours. The mixture is allowed to stand at room temperature overnight and is cooled. The potassium muconate and potassium bromide are filtered (Note 9), washed on the funnel with two 350-ml. portions of methanol and 400 ml. of ether, transferred without further drying to an enameled 11- to 12-l. pail, and dissolved in 8 l. of hot water. The aqueous solution, to which is added 30 g. of Norit, is heated to boiling by introduction of steam, filtered through a Norit filter pad by suction, and cooled in an ice-salt bath. The muconic acid is precipitated by the addition of a large excess (1.5 l.) (sp. gr. 1.18) of concentrated hydrochloric acid to the cold solution. The acid is added in a thin stream to the well-stirred solution. After 2 hours the muconic acid is filtered, washed first with two 400-ml. portions of cold water and then with 200 ml. of methanol, and dried at 85°. The yield of nearly colorless product melting at 296–298°, with decomposition, amounts to 165–195 g. (37–43%).