In a
1.5-l. Erlenmeyer flask to which is attached a
reflux condenser,
190 g. (0.88 mole) of methyl sebacamate (p. 613) is dissolved in
200 ml. of boiling tetrachloroethane. The solution is allowed to cool to 40–50° (Note
1),
95 g. (0.67 mole) of phosphorus pentoxide is added (Note
2), and the mixture is stirred well by means of a
glass rod. The mixture is heated in an
oil bath to 120° (
thermometer in oil), and a second
95-g. portion of phosphorus pentoxide is added. After the mixture has been heated at 145° for 30 minutes with occasional hand stirring, the liquid is decanted. The residue is heated at 145° with
200 ml. of tetrachloroethane for 30 minutes with occasional stirring, and the liquid is decanted. This process is repeated once. The combined extracts are placed in a
1-l. flask, and most of the solvent is distilled under the reduced pressure of a
water pump. The residue is transferred to a
300-ml. flask, and the remainder of the solvent is removed (Note
3). When no more distillate comes over, the
receiver is changed, the water pump is replaced by an
oil pump, and the residue is fractionated (Note
4). The yield of
methyl ω-cyanopelargonate boiling at
121–124°/1 mm. (Note
5) is
119–124 g. (
69–71%).