A
3-l. three-necked flask equipped with a
stirrer,
reflux condenser, and
gas inlet tube is charged with
476 g. (3.45 moles) of furylacrylic acid2 and
1580 g. (about 33 moles) of 95% ethanol (Note
1). The mixture is heated to boiling, and anhydrous
hydrogen chloride is introduced at such a rate that the mixture becomes saturated after 90 minutes. The gas inlet tube is replaced by a stopper, and a
2-ft. Vigreux column is substituted for the reflux condenser. About 250 ml. of solvent is removed by distillation at atmospheric pressure; then another 300 ml. is removed while the pressure is slowly reduced (
water aspirator). The residue is cooled and stirred with a solution of about
260 g. of sodium carbonate in water (Note
2). The mixture is extracted with two
250-ml. portions of benzene, and the combined extracts are washed with 100 ml. of water (Note
3). Distillation of the organic portion through a 2-ft. Vigreux column yields, after a small fore-run,
579–657 g. (
73–83%) of
diethyl γ-oxopimelate, b.p.
116–121° /0.3 mm.,
nD25 1.4395–1.4400.