In a
2-l. three-necked flask, fitted with a
sealed mechanical stirrer (Note
1), a
reflux condenser protected with a calcium chloride tube, and a
dropping funnel, is placed
123 g. (1 mole) of nicotinic acid (Note
2). The stirrer is started, and
500 ml. (818 g., 6.9 moles) of distilled thionyl chloride is added in a slow stream over a period of 15–20 minutes (Note
3). After the addition is complete, the mixture is heated on the
steam bath with continuous stirring for 1 hour; then the reflux condenser is replaced by one set for downward distillation, and the excess
thionyl chloride is removed by distillation at reduced pressure as heating on the steam bath is continued (Note
1) and (Note
3). After most of the
thionyl chloride has been distilled,
200 ml. of anhydrous benzene is added, and the
benzene is distilled at reduced pressure. An additional
500 ml. of anhydrous benzene is added; then the flask is fitted with a
thermometer and a reflux condenser and is placed in an
ice-salt bath. The stirrer is started, and
330 g. (2.5 moles) of anhydrous aluminum chloride is added in portions over a period of 1 hour as the internal temperature is held between 5° and 10°. The
ice bath is removed, and the flask is permitted to warm to room temperature and is finally heated under reflux for 6 hours.
The dark red-brown reaction mixture is cautiously poured onto a mixture of 2 kg. of ice and
200 ml. of concentrated hydrochloric acid. The organic layer is separated and discarded. The acid solution is extracted with three
500-ml. portions of ether (Note
4), which are discarded; then it is treated with
50% aqueous sodium hydroxide until the
aluminum hydroxide which first forms redissolves (Note
5). After cooling, the organic material is extracted with five
300-ml. portions of chloroform. The combined
chloroform extracts are washed with water, the solvent is removed by distillation on the steam bath, and the product is distilled. The yield of
3-benzoylpyridine (Note
6), b.p.
107–110°/0.3 mm. or
141–145°/4 mm., is
165–175 g. (
90–96%),
nD26 1.6088.