A
2-l., three-necked, round-bottomed flask equipped with a
Trubore stirrer and
paddle is charged with
172.8 g. (1.200 moles) of 1,1-cyclobutanedicarboxylic acid (Note
1) and
1500 ml. of benzene. The mixture is stirred and heated at reflux, and
200 ml. of benzene and
benzene-water azeotrope is removed by distillation to ensure anhydrous conditions. The flask is then fitted with an
addition funnel and a
reflux condenser attached to a
drying tube. Stirring and heating are continued, and over a 40-minute period,
170 g. (102 ml., 1.26 moles) of sulfuryl chloride (Note
2) is added from the funnel, while
4.0 g. of benzoyl peroxide (Note
3) is added simultaneously in small portions through the top of the condenser. After a short induction period,
hydrogen chloride and
sulfur dioxide are evolved. After the addition is complete, heating at reflux is maintained for 22 hours. The solid is dissolved after 1 hour, leaving a light brown solution. After the heating period is complete, the
benzene is removed by distillation, and the residue is heated to 190–210° for 45 minutes to effect decarboxylation. The black residue is transferred to a small flask and distilled under vacuum through a
6-cm. Vigreux column. After a forerun of about
25–30 g. (Note
4),
65–79 g. (
40–49%) of
cis- and trans-3-chlorocyclobutanecarboxylic acid is collected as a light yellow liquid, b.p.
131–137° (15 mm.) nD24 1.4790 (Note
5). A black residue remains in the distillation flask.