Submitted by Walter H. Hartung and Frank Crossley.
Checked by Reynold C. Fuson and R. F. Peterson.
1. Procedure
A
3-l. three-necked, round-bottomed flask (A,
.htmFig. 11) is provided with a
reflux condenser,
liquid-sealed mechanical stirrer, and
two gas delivery tubes (T
1 and T
2) which extend as far as possible into the flask.
Methyl nitrite is generated in a
2-l. Erlenmeyer flask B which is fitted with a
500-cc. dropping funnel C and connected to A by the tube T
1. Dry
hydrogen chloride is introduced through T
2. The apparatus is assembled preferably in a hood with effective draft.
Fig. 11
In A is placed a solution of
469 g. (3.5 moles) of propiophenone (Note
1) in
2.3 l. of ordinary ethyl ether, and in B a mixture of
290 g. (4 moles) of 95 per cent sodium nitrite,
180 cc. (142 g., 4.5 moles) of methyl alcohol, and 170 cc. of water. In the dropping funnel C is placed
455 cc. of cold dilute sulfuric acid (prepared by adding one volume of concentrated acid to two volumes of water).
The stirrer is started, and
hydrogen chloride is introduced through T
2 at the rate of 6–10 bubbles a second. The acid in C is allowed to drop slowly into B, and the gaseous
methyl nitrite (Note
2) is introduced through T
1 into the reaction mixture. The solution in A develops a brown-red color, and after about ten minutes the ether begins to reflux gently (Note
3). The rate of evolution of
methyl nitrite is then adjusted so that the ether continues to reflux gently. About four hours is required for addition of the
methyl nitrite. Stirring and addition of
hydrogen chloride are continued for thirty minutes longer; at the end of this time the solution has ceased boiling and has assumed a clear yellow color.
The reaction mixture is allowed to stand for several hours (preferably overnight) and is then extracted repeatedly with
500-cc. portions of 10 per cent sodium hydroxide solution, until the alkaline extracting medium remains practically colorless when shaken with the ethereal solution (Note
4). Usually five
500-cc. portions of the sodium hydroxide solution are required. The combined alkaline extracts are poured slowly, with stirring, into a mixture of
700–750 cc. of concentrated hydrochloric acid and about 1 kg. of ice. The crystals of
isonitrosopropiophenone are filtered with suction and dried. The product weighs
370–390 g. (
65–68 per cent of the theoretical amount) and melts at
111–113°. This material can be crystallized from about
550 cc. of toluene and yields
315–335 g. of snow-white crystals, m.p.
112–113° (Note
5).
2. Notes
2. For the preparation of small amounts of the isonitrosoketone it is more convenient to employ a higher-boiling alkyl nitrite, such as
butyl nitrite (p. 108), which can be added directly to the reaction mixture by substituting a
dropping funnel for the tube T
1.
Butyl nitrite must be freshly prepared or redistilled shortly before use.
3. The rate of stirring must be kept fairly constant since an abrupt increase in speed may cause the
ether to boil at a dangerous rate.
4. The ethereal solution remaining from the alkaline extractions contains unreacted
propiophenone which may be recovered by distilling the
ether and fractionating the residue. The amount of recovered
propiophenone, collected at 210–216°, varies from 80 to 110 g.
5. About 25–30 g. of material may be recovered from the
toluene mother liquor by extraction with alkali and reprecipitation with acid.
3. Discussion
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