A
1-l., three-necked flask is charged with
95 g. (0.36 mole) of triphenylphosphine (Note
1) and
500 ml. of anhydrous benzene, and fitted with a
gas-inlet (Note
2), a
mechanical stirrer, and a
condenser with attached drying tube. The flask is cooled in an
ice bath, stirring is begun, and
chlorine is introduced through the gas-inlet.
Dichlorotriphenylphosphorane separates as a white solid or as a milky oil; the flow of
chlorine is discontinued when the mixture develops a strong lemon-yellow color (Note
3). The gas inlet is quickly replaced by an
addition funnel, and a solution of
10 g. of triphenylphosphine in 60 ml. of benzene is added dropwise fairly rapidly (Note
4). A solution of
24.5 g. (0.250 mole) of 1,2-epoxycyclohexane (Note
5) in
50 ml. of benzene is then added dropwise over
ca. 20 minutes. The ice bath is replaced by a
heating mantle, and the mixture, which consists of two liquid phases, is stirred and refluxed for 4 hours. It is then cooled, and excess
dichlorotriphenylphosphorane is destroyed by the slow addition of
10 ml. of methanol (Note
6). The mixture is concentrated on a
rotary evaporator at
ca. 100 mm., and the residue, which may be a white solid or a viscous oil, is triturated with
300 ml. of petroleum ether (30–60°). The solid
triphenylphosphine oxide that separates is collected by suction filtration. The cake is thoroughly broken up with a
spatula and washed with three
100-ml. portions of petroleum ether. The combined filtrates, from which a little more
triphenylphosphine oxide precipitates, are refiltered, then washed with
250-ml. portions of aqueous 5% sodium bisulfite (Note
7) and with water. The organic phase is dried over
magnesium sulfate, filtered, concentrated on a rotary evaporator at
ca. 100 mm., and distilled through a
20-cm. Vigreux column. There is very little forerun before
27–28 g. (
71–73%) of
cis-1,2-dichlorocyclohexane is collected at
105–110° (33 mm.),
nD25 1.4977 (Note
8).