A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1925, 4, 57
DOI: 10.15227/orgsyn.004.0057
[Hydroxylamine, N-phenyl-]
Submitted by Oliver Kamm
Checked by C. S. Marvel
1. Procedure
In a 16-l. earthenware jar are placed 250 g. (4.7 moles) of technical ammonium chloride, 8 l. of water, and 500 g. (416 cc., 4.1 moles) of nitrobenzene. The mixture is stirred vigorously by means of a mechanical stirrer, and 620 g. (8.1 atoms) of zinc dust of 85 per cent purity is added (Note 1) during the course of fifteen to twenty minutes (Note 2). As the reduction proceeds, the temperature rises to 60–65°. Stirring is continued for fifteen minutes after all the zinc dust has been added, at the end of which time the reaction is complete, as indicated by the fact that the temperature of the mixture ceases to rise.
While still hot, the solution is filtered with suction in order to remove the zinc oxide, which is washed with 1 l. of hot water. The filtrate is placed in an enameled pan, saturated with salt, about 3 kg. being required, and cooled to 0° by being placed in an ice-salt mixture. The phenylhydroxylamine, which crystallizes out in long, light yellow needles (Note 3), is filtered by suction. The yield of crude product varies considerably, depending upon the amount of salt solution present, but averages 350–400 g. This corresponds to 275–300 g. (62–68 per cent of the theoretical amount) of actual phenylhydroxylamine, as determined by its separation from inorganic materials by solution in ether (Note 4).
Since phenylhydroxylamine deteriorates upon storage, it is generally used promptly, as illustrated in the preparation of cupferron (p. 177). The oxalate is somewhat more stable.
2. Notes
1. The zinc dust must be analyzed (Gattermann, "Practical Methods of Organic Chemistry," 3rd ed., p. 390), and a proportional quantity used if the zinc content is not 85 per cent. Technical nitrobenzene is satisfactory if it distils over a range of not more than 5° and is not acid in reaction.
2. When the reaction is run more slowly, the temperature does not reach 60–65° and the yield is poorer. At 50–55°, the yield is about 55 per cent.
3. It is important that the phenylhydroxylamine solution be kept at 0° for at least one-half hour or considerable material will be lost in the solution. The use of an enameled pail saves a great deal of time at this step.
4. Phenylhydroxylamine is soluble in saturated salt solution at 0° to the extent of about 9 g. per liter, but this amount is not included in the yields given. Occasional yields of 300–310 g. of dry phenylhydroxylamine have been obtained.
3. Discussion
β-Phenylhydroxylamine can be prepared by the reduction of nitrobenzene by zinc dust,1 a method in which various solvents and catalysts have been used, and in which copper-coated and amalgamated zinc, as well as aluminum amalgam,2 have been substituted for the zinc dust; by ammonium sufide;3 by sodium in liquid ammonia;4 and by the oxidation of anilinomagnesium bromide with an ether solution of hydrogen peroxide.5 The procedure described is like an earlier method,6 but it has been found7 that cooling is not essential. The preparation of the oxalate has been described.8

References and Notes
  1. Bamberger, Ber. 27, 1348, 1548 (1884); Wohl, Ber. 27, 1432 (1894).
  2. Wislicenus, Ber. 29, 494 (1896); Lapworth and Pearson, J. Chem. Soc. 119, 767 (1921); Kasanof, J. Ind. Eng. Chem. 12, 799 (1920).
  3. Willstätter and Kubli, Ber. 41, 1936 (1908); Slotta and Jacobi, Z. anal. Chem. 80, 97 (1930).
  4. White and Knight, J. Am. Chem. Soc. 45, 1784 (1923).
  5. Oddo and Binaghi, Gazz. chim. ital. 54, 193 (1924); Atti accad. Lincei 32, II, 349 (1923) [C. A. 18, 3166 (1924)]; Durand and Naves, Compt. rend. 180, 521 (1925).
  6. Kalle and Co., Ger. pat. 89,978 [Frdl. 4, 47 (1894–97)].
  7. Marvel and Kamm, J. Am. Chem. Soc. 41, 277 (1919).
  8. Sulzberger, U. S. pat. 1,390,260 [C. A. 16, 105 (1922)].

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)


copper-coated and amalgamated zinc

ammonium sufide

sodium in liquid ammonia

ether (60-29-7)

ammonium chloride (12125-02-9)

aluminum (7429-90-5)

zinc (7440-66-6)

Nitrobenzene (98-95-3)

hydrogen peroxide (7722-84-1)

Cupferron (135-20-6)

Hydroxylamine, N-phenyl- (100-65-2)

zinc oxide

anilinomagnesium bromide