The percentage yields have been based on the amount of aniline taken. It would probably be more legitimate to base the calculation on the amounts of aniline taken and of nitrobenzene not recovered, since undoubtedly the latter is reduced to aniline during the course of the reaction. If this be done, the yield is found to be only 55 to 60 per cent of the calculated amount.
In a number of experiments, the glycerol used contained an appreciable amount of water. Under these conditions, the yield of product is much lower. "Dynamite" glycerol containing less than half a per cent of water is best employed; U. S. P. glycerol contains 5 per cent of water and usually gives lower yields.
3. Other Methods of Preparation
Quinoline has been produced by passing the vapor of allylaniline over red-hot lead oxide;[1a] by heating acrylideneaniline, or better, a mixture of aniline, glycerol and sulfuric acid;[2a] by heating aniline with glycerol and sulfuric acid, using nitrobenzene as an oxidizing agent;[1] by treating a mixture of glyoxal and o-toluidine with alkali;[2] by treating a solution of o-aminobenzaldehyde with acetaldehyde and alkali;[3] by heating methylacetanilide with zinc chloride;[4] by heating aminoazobenzene with glycerol and sulfuric acid;[5] by heating a mixture of aniline, glycerol and sulfuric acid with arsenic acid.[6]
[1a] Ber. 12, 453 (1879).
[2a] Ber. 13, 911 (1880); Monatsh. 1, 316 (1880).
[1] Monatsh. 2, 141 (1881); J. prakt. Chem. (2) 49, 549 (1894),
[2] Monatsh. 15, 277 (1894).
[3] Ber. 15, 2574 (1882); 16, 1833 (1883).
[4] Ber. 23, 1903 (1890).