B.
2-Cyano-6-methylpyridine. In a
2-l., three-necked, round-bottomed flask equipped with a Hershberg stirrer, a 500-ml. pressure-equalizing, dropping funnel without a stopper, and a thermometer-gas inlet adapter (Note
6) fitted with a thermometer which reaches deep into the flask is placed a solution of
147 g. (3.0 mole) of sodium cyanide dissolved in 400 ml. of water. The stirrer is started and the apparatus is flushed with prepurified
nitrogen for 1 hour (Note
7). The solution in the flask is then cooled to 0° with an
ice bath, and a solution of
235 g. (1.0 mole) of 1-methoxy-2-methylpyridinium methyl sulfate dissolved in 300 ml. of water is added dropwise over a period of 2 hours. The dropping funnel and the thermometer-adapter are then quickly removed and replaced by stoppers, and the flask is allowed to stand in a refrigerator overnight (12–16 hours). The flask, containing needles of the crude nitrile (Note
8), is removed from the refrigerator and the contents stirred at room temperature for 6 hours. After addition of
200 ml. of chloroform, the contents of the flask are transferred to a large
separatory funnel and the layers separated. Extraction of the aqueous phase is repeated twice with
100-ml. portions of chloroform, and the combined extracts are dried over anhydrous
magnesium sulfate. After removal of the drying agent by filtration, the filtrate is concentrated on a steam bath to remove
chloroform, and the residual crude
cyanopicoline (90–110 g.) is transferred, while hot, to a distilling flask. Distillation under reduced pressure (30 mm.) (Note
9) gives three fractions: Fraction I, b.p.
99–106°, weighs
15–20 g.; Fraction II, b.p. 106–124°, weighs 5–10 g.; and Fraction III, b.p.
125–131°, weighs
60–70 g. (Note
10). Fraction III is dissolved in
1 l. of hot 10% ethyl alcohol, treated with
0.5 g. of activated carbon, filtered, and the filtrate is allowed to cool slowly to room temperature. The
2-cyano-6-methylpyridine separates as white prismatic needles, m.p.
71–73°, and weighs
48–54 g. (
40–46% based on
2-picoline-1-oxide) (Note
11) and (Note
12).