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Organic Synteses vol 4 - Kamm O.

Kamm O., Adams R. Organic Synteses vol 4 - John Wiley & Sons, 1952. - 48 p.
Download (direct link): organicsynthesesvol41925.pdf
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After stirring has been continued for two hours longer, the crock is surrounded by hot water or steam and warmed to 50 without stirring. The mixture is then allowed to stand until cool, when the aqueous layer is drawn off by means of a siphon. The upper oily layer is transferred to a 12-I. flask and distilled in a current of steam until no more oil passes over; about 10 1. of distillate is collected (Note 6). The water is drawn off and the benzene removed by distillation, by means of a 2-1. round-bottom flask and a fractionating column about 90 cm. long. When benzene no longer distils over, the distillation is continued in the same apparatus under reduced pressure, and the fraction that boils at 94-96/20 mm. is collected. A small amount of dark-colored residue remains in the flask. The yield of almost colorless o-tolunitrile is 300-330 g. (64-70 per cent of the theoretical amount).
^-Tolunitrile can be prepared in exactly the same manner from ^-toluidine; the product, which distils at 104-1060/20 mm., solidifies in the receiver to a mass of nearly colorless needles which melt at 2 5-2 7 . The yield is the same as with the ortho compound (Note 7).
o-TOLUNITRILE AND /.-TOLUNITRILE
71
2. Notes
1. If desired, the cuprous chloride may be suspended in 3 1. of water and the sodium cyanide added in the solid form.
2. If several runs are to be made it may be more convenient to prepare a large quantity of cuprous cyanide solution, since this appears to be stable for several days.
3. If the sodium nitrite is not of the highest technical purity it may be necessary to employ more than the indicated quantity. It is essential that the test for nitrous acid be permanent; if any unchanged amine remains, a precipitate of the diazoamino compound is formed on neutralization. A moderate excess of nitrite does not appear to interfere with the reaction, especially since the greater portion of the free nitrous acid is removed by the carbon dioxide liberated on neutralization.
4. Sodium carbonate is preferable to sodium hydroxide-because very little heat is evolved on neutralization. A slight excess of carbonate does not appear to be harmful.
5. It is essential that the stirring be very vigorous. If the intermediate addition compound is allowed to collect on the surface of the liquid, it decomposes spontaneously with evolution of much heat; this decomposition may take place with almost explosive violence. The presence of the benzene tends to diminish the viscosity of the intermediate product and permit it to be readily distributed throughout the mixture. Decomposition is quite rapid at o and is practically complete when room temperature is reached; it appears, however, to be advisable to warm the mixture to 50, since if this be omitted the yield is slightly decreased.
6. The apparatus described in Org. Syn. 2, So, is suitable for the steam distillation.
7. The product, as obtained in the above procedure, is of high purity; cresols do not appear to be formed under the conditions specified. The process has the advantage over that described in the literature 1 of giving rise to no poisonous fumes during the formation of the cuprous cyanide and during the interaction of this with the diazonium salt. The yield is practically the same as in the older method.
72
ORGANIC SYNTHESES
3. Other Methods of Preparation
The original method of Sandmeyer 1 prescribed the preparation of the cuprous cyanide solution by dissolving copper sulfate in potassium cyanide solution and adding the strongly acid diazonium solution to it. Both of these operations involve the evolution of poisonous gasescyanogen in the first case and hydrogen cyanide in the second. Slight modifications have been subsequently suggested: the use of a 50 per cent excess of cuprous cyanide 2 and the heating of the cuprous cyanide solution before the reaction.3
o-Tolunitrile has also been prepared from o-toluidine by conversion into o-tolyl isothiocyanate and the boiling of this under a reflux condenser; 4 ^-tolunitrile has been prepared by distilling /i-toluic acid with potassium thiocyanate; 5 and a mixture of the two has been produced by the interaction of toluene, mercury fulminate, and aluminium chloride.6
1 Ber. 17, 2653 (1884); 18, 1492, 1496 (1885).
2 Ber. 19, 756 (1886).
3 Ber. 23, 1026 (1890).
4 Ber. 6, 419 (1873).
6 Ber. 8, 441 (1875).
6 Ber. 36, 14 (1903).
XXVI
p-TOLUYL-o-BENZOIC ACID
64()20+65 (AlaCle)
Prepared by L. F. Fieser.
Checked by Roger Adams and R. L. Shriner.
1. Procedure
A 2-1. round-bottom flask is clamped to a ring-stand and equipped with a rubber stopper protected with tin foil and carrying a glass stirrer with mercury seal and a reflux condenser. (Cf. Org. Syn. i, 4, Fig. i, a.) As an outlet for the hydrogen chloride, the top of the condenser is provided with a bent tube which almost touches the surface of the water in a half-filled
i-l. flask.
One hundred grams of phthalic anhydride and 400 g. of toluene are placed in the flask, which is cooled in an ice bath while 200 g. of anhydrous aluminium chloride (Note 1) is being ground to a fine powder. The chloride is now added all at once, and connections to the condenser made as rapidly as possible. Stirring is commenced at once and the ice bath is removed. The mixture warms up considerably and becomes olive-green in color. When the evolution of hydrogen chloride begins to slacken (ten minutes) a water bath is put into place and heated to ()o in the course of forty-live minutes. The temperature of the bath is kept at yo and vigorous stirring continued for two and one-half hours. At this point, the evolution of hydrogen chloride will have practically ceased and the reaction will have been completed. The hot. water in the bath is replaced first by cold water and then by ice, while stirring is continued.
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