Organic Syntheses Part 10

If a good grade of cyanide be used, it is not necessary to add bone-black in order to obtain the acid in a pure state.

In making experiments with 500 g. of _p_-nitrobenzyl cyanide, it was found that the time for hydrolysis was about the same as when smaller amounts were used.

3. Other Methods of Preparation

_p_-Nitrophenylacetic acid has been formed by the nitration of phenylacetic acid;[1] by the hydrolysis of its ester[2] or its amid,[3]

and by the hydrolysis of its nitrile with hydrochloric acid.[4]

[1] Ber. 42, 3596 (1909).

[2] Ber. 12, 1765 (1879).

[3] Ber. 14, 2342 (1881).

[4] Ber. 15, 834 (1882).

XVI

NITROSO-b-NAPHTHOL

C10H7OH(b) + HNO2--> C10H6(OH)NO(1,2) + H2O

Prepared by C. S. MARVEL and P. K. PORTER. Checked by H. T. CLARKE and W. W. HARTMAN.

1. Procedure

IN a 12-l. round-bottom flask fitted with a mechanical stirrer are placed 500 g. of technical b-naphthol dissolved in a warm solution of 140 g.

of sodium hydroxide in 6 l. of water. The solution is cooled to 0'0 in an ice-and-salt bath, and 250 g. of powdered technical sodium nitrite is added. Stirring is started and 1100 g.

of sulfuric acid (sp. gr. 1.32) are added from a dropping funnel, at such a rate that the whole is added in one to one and a half hours, the temperature being kept at 0'0. During the reaction crushed ice is added from time to time to maintain the temperature at 0'0; about 1 kg. is usually used. After all of the sulfuric acid has been added, the solution should react acid to Congo paper.

The mixture is stirred one hour longer at the low temperature and then the nitroso-b-naphthol, which has gradually separated out during the reaction, is filtered with suction and washed thoroughly with water. The product is at first light yellow in color, but after three to four days it gradually changes to a dark brown.

The moisture content seems to have some effect on the color.

After the product has been air-dried for about four days, the yield is about 665 g.; it melts at 97'0. A sample of this partially dried product, on drying _in vacuo_ over sulfuric acid for twenty hours, loses about 10 per cent of its weight and the melting point is 106'0.

By longer drying under ordinary conditions, the melting point of 106'0 is reached. The total yield of dry product is about 595 g.

(99 per cent of the theoretical amount).

This product is satisfactory for all purposes. It may be obtained in a crystalline condition, however, by recrystallizing from hot ligroin (sp. gr. 0.71-0.72). About 2 g. of nitroso-b-naphthol will dissolve in 15 cc. of boiling ligroin. The product is not very soluble in cold ligroin, so that nearly all is recovered.

2. Notes

It is very necessary to keep the temperature near 0'0 while adding the sulfuric acid, or a tarry product will be obtained.

Vigorous stirring and the addition of the sulfuric acid at the proper rate are essential for a good product.

A large vessel is needed for the reaction, as the nitroso-b-naphthol separates in a finely divided condition and there is some tendency to foam.

The final air-dried product is pure except for its moisture content, as is shown by the fact that on drying _in vacuo_ it has a very good melting point. A sample of Kahlbaum's nitroso-b-naphthol melted at 101--105.

3. Other Methods of Preparation

Nitroso-b-naphthol has been made by the action of hydroxylamine hydrochloride on b-naphtho-quinone-chlorimide;[1] by the action of sulfuric acid upon a solution of pota.s.sium or sodium nitrite and the sodium salt of b-naphthol;[2] by the action of sodium nitrite upon an alcoholic solution of zinc chloride and b-naphthol;[3]

by the action of sodium nitrite upon b-naphthol suspended in zinc sulfate solution;[4] by the action of nitrous acid on b-dinaphthol methane;[5] and by the action of nitrosyl sulfate upon the sodium salt of b-naphthol.[6]

[1] Ber. 27, 241 (1894).

[2] Ber. 8, 1026 (1875); 27, 3076 (1894); J. Chem. Soc. 45, 295 (1884).

[3] Ber. 18, 705 (1885).

[4] D. R. P. 25,469; Frdl. 1, 335 (1883).

[5] Ber. 33, 806 (1900).

[6] J Chem. Soc. 32, 47 (1877); Ann. 189, 146 (1877).

XVII

PHENYLACETIC ACID

C6H5CH2CN + 2H2O + H2SO4--> C6H5CH2CO2H + NH4HSO4

Prepared by ROGER ADAMS and A. F. THAL. Checked by O. KAMM and A. O. MATTHEWS.

1. Procedure

IN a 5-l. round-bottom flask, fitted with a mechanical stirrer and reflux condenser, are mixed 1150 cc. of water, 840 cc.

of commercial sulfuric acid and 700 g. of benzyl cyanide (preparation III, p. 9). The mixture is heated under a reflux condenser and stirred for three hours, cooled slightly and then poured into 2 l.

of cold water. The mixture should be stirred so that a solid cake is not formed; the phenylacetic acid is then filtered off.

This crude material should be melted under water and washed by decantation several times with hot water. These washings, on cooling, deposit a small amount of phenylacetic acid which is filtered off and added to the main portion of material.

The last of the hot water is poured off from the material while it is still molten and it is then transferred to a 2-l. Claisen distilling flask and distilled _in vacuo_. A small amount of water comes over first and is rejected; about 20 cc., containing an appreciable amount of benzyl cyanide, then distils. This fraction is used in the next run. The distillate boiling 176-189'0/50 mm.

is collected separately and solidifies on standing. It is practically pure phenylacetic acid, m. p. 76-76.5'0; it amounts to 630 g.

(77.5 per cent of the theoretical amount). As the fraction which is returned to the second run of material contains a considerable portion of phenylacetic acid, the yield actually amounts to at least 80 per cent.

For the preparation of small quant.i.ties of phenylacetic acid, it is convenient to use the modified method given in the Notes.

2. Notes

The standard directions for the preparation of phenylacetic acid specify that the benzyl cyanide is to be treated with dilute sulfuric acid prepared by adding three volumes of sulfuric acid to two volumes of water. There action, however, goes so vigorously that it is always necessary to have a trap for collecting the benzyl cyanide which is blown out of the apparatus.

The use of the more dilute acid, as described in the above directions, is more satisfactory.

The phenylacetic acid may also be made by boiling under a reflux condenser for eight to fifteen hours, without a stirrer, but this method is not nearly so satisfactory as that described in the procedure.