In a
5-l. three-necked flask, filled with
nitrogen,
110 g. (1.0 mole) of recrystallized catechol (Note
1) is dissolved in 250 ml. of deaerated water (Note
2) containing
88 g. (2.2 moles) of sodium hydroxide. The flask is fitted with a
gas inlet tube, a
thermometer dipping into the liquid, and an
efficient glass mechanical stirrer with a
gas-tight rubber slip seal and is immersed in an
ice-salt bath. A positive
nitrogen pressure of about 1 cm. is maintained by attaching the inlet tube to a source of
nitrogen through a line containing a T-tube dipping into
mercury. A solution of
200–225 g. (2.0–2.3 moles) of commercial phosgene in 750 ml. of toluene is prepared at 0° by bubbling the gas into
toluene in a
tared flask (Note
3), and the solution is added to the flask in portions of about 50 ml. with good mechanical stirring over a period of 60 to 75 minutes. During the addition the temperature is maintained at 0–5° by periodic addition to the mixture of clean cracked ice, free from dirt and
iron rust. After addition of the
toluene solution of
phosgene is completed, the mixture is stirred at 0–5° for 1 hour and then allowed to come to room temperature. The mixture is filtered with suction, and the solid is pressed on the funnel to remove as much water as possible. The aqueous portion of the filtrate is separated, and the solid on the funnel is added to the
toluene in the filtrate and dissolved by warming. The warm
toluene solution is filtered and distilled under reduced pressure (
water aspirator) until the product begins to crystallize. The residue is warmed to redissolve the solid, and then chilled. The
o-phenylene carbonate is collected on a
suction filter and dried in a
vacuum desiccator; the yield is
98–110 g., m.p.
119–120°.
Concentration of the filtrate yields a second crop of impure product, which is recrystallized from
toluene and then melts at
119–120°. The combined yield of pure white
o-phenylene carbonate from the first and second crops is
107–116 g. (
79–85%).