Org. Synth. 1928, 8, 24
DOI: 10.15227/orgsyn.008.0024
Submitted by F. Y. Wiselogle and H. Sonneborn, III.
Checked by C. S. Marvel and J. F. Kaplan.
1. Procedure
In a 3-l. round-bottomed flask fitted with a mechanical stirrer are placed 200 g. of technical flake sodium hydroxide, 200 g. of benzophenone, 2 l. of 95 per cent alcohol, and 200 g. of technical zinc dust. The stirrer is started and the mixture slowly warms to about 70° spontaneously. After two to three hours the mixture, which has started to cool, is filtered with suction, and the residue is washed twice with 100-cc. portions of hot alcohol (Note 1).
The filtrate is poured into five volumes of ice water acidified with about 425 cc. of concentrated commercial hydrochloric acid. The benzohydrol separates as a white crystalline mass and is filtered by suction. The yield of crude air-dried product melting at 65° is 194–196 g. (96–97 per cent of the theoretical amount). From 200 g. of crude product in 200 cc. of hot alcohol there is obtained, after cooling in an ice-salt mixture, filtering, and drying, 140–145 g. of product melting at 68°. The benzohydrol remaining in the mother liquors may be precipitated with water.
2. Notes
1. The filtered zinc dust is inflammable; it must not be allowed to dry in contact with combustible material.
3. Discussion
Benzohydrol can be prepared by reducing benzophenone with sodium amalgam;1 with metallic calcium and alcohol;2 with hydrogen in the presence of a catalyst;3 with zinc, aluminum, or sodium in strongly alkaline solutions;4 with zinc dust and alcoholic potassium hydroxide solution;5 electrolytically;6 with magnesium and absolute alcohol;7 with magnesium and ammonium chloride in 95 per cent alcohol;7 with isopropyl alcohol and a little sodium isopropoxide;8 and with aluminum isopropoxide.9

References and Notes
  1. Linnemann, Ann. 125, 230 (1863); 133, 6 (1865).
  2. Marschalk, Ber. 43, 642 (1910).
  3. Vavon, Compt. rend. 155, 287 (1912).
  4. Böeseken and Cohen, Verhandel Akad. Wetenschappen Amsterdam, 16, 91 (1913) [Chem. Zentr. I, 1375 (1915)].
  5. Montagne, Rec. trav. chim. 25, 402 (1906).
  6. Müller, Z. Electrochem. 16, 240 (1910).
  7. Zeckmeister and Rom, Ann. 468, 117 (1929).
  8. Bachmann, J. Am. Chem. Soc. 55, 391 (1933).
  9. Lund, Ber. 70, 1520 (1937).

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


alcohol (64-17-5)

hydrochloric acid (7647-01-0)

ammonium chloride (12125-02-9)

hydrogen (1333-74-0)

sodium hydroxide (1310-73-2)

magnesium (7439-95-4)

aluminum (7429-90-5)

potassium hydroxide (1310-58-3)

Benzophenone (119-61-9)

zinc (7440-66-6)

calcium (7440-70-2)

sodium (13966-32-0)

isopropyl alcohol (67-63-0)

sodium isopropoxide (683-60-3)

aluminum isopropoxide