A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1958, 38, 26
DOI: 10.15227/orgsyn.038.0026
[Acetaldehyde, diphenyl-]
Submitted by Donald J. Reif and Herbert O. House1.
Checked by M. S. Newman and W. H. Powell.
1. Procedure
In a 1-l. separatory funnel is placed a solution of 39.2 g. (0.2 mole) of trans-stilbene oxide (Note 1) in 450 ml. of reagent benzene. To the solution is added 13.2 ml. (0.1 mole) of boron trifluoride etherate (Note 2). The solution is swirled, allowed to stand for 1 minute (Note 3), and then washed with two 300-ml. portions of water. The organic layer is separated, and the benzene is removed by distillation (Note 4). The residual crude aldehyde is purified by distillation under reduced pressure. The product, collected at 115–117°/0.6 mm., amounts to 29–32 g. (74–82%), nD25 1.5875–1.5877 (Note 5).
2. Notes
1. The trans-stilbene oxide (p.860) should be free of trans-stilbene, since the stilbene, if present, is not altered by the reaction conditions and will contaminate the final product.
2. A practical grade of boron trifluoride etherate, purchased from Eastman Kodak Company, was redistilled before use. The pure etherate boils at 126°.
3. Longer reaction times result in a marked decrease in the yield of diphenylacetaldehyde.
4. The submitters found that distillation of the benzene solution is necessary to obtain an anhydrous product. If the benzene solution is dried over magnesium sulfate and the benzene removed under reduced pressure, the diphenylacetaldehyde is contaminated with water.
5. The product obtained by this procedure, when treated with 2,4-dinitrophenylhydrazine,2 produced the 2,4-dinitrophenylhydrazone of diphenylacetaldehyde, m.p. 146.8–147.8°, in 94% yield.
3. Discussion
Diphenylacetaldehyde has been prepared by the isomerization of 1,2-dihydroxy-1,2-diphenylethane either thermally3 or in the presence of sulfuric acid,4,5,6 oxalic acid,7 or acetic anhydride.8 The aldehyde has also been produced by the reaction of 2,2-dipheny1-2-hydroxyethyl ether with sulfuric acid6,7 or oxalic acid;7,9 by the reaction of hydrochloric acid with 2-amino-1,1-diphenylethanol;10 by the reaction of hydrobromic11 or hydrochloric12 acid with 2-diethylamino-1,1-diphenylethanol; by the hydrolysis of β,β-diphenylvinyl ethyl ether;13 by the thermal rearrangement of deoxybenzion;14 by the hydrolysis and decarboxylation of the glycidic ester obtained from ethyl chloroacetate and benzophenone;15 by passing a mixture of diphenylacetic and formic acid over thorium oxide on pumice at 450°;16 and by the hydrolysis of diphenylacetaldehyde enol methyl ether (obtained from benzophenone and methoxymethylenetriphenylphosphorane).17
Diphenylactaldehyde also has been prepared by the isomerization of trans-stilbene oxide in the presence of sodium bisulfite18 or lithium diethylamide,19 or by the isomerization of either cis- or trans-stilbene oxide in the presence of boron trifluride etherate.2 The procedure chosen illustrates the ready isomerization of substituted ethylene oxides to carbonyl compounds. The procedure is applicable to substituted epoxides in which one of the carbon atoms of the oxirane ring is bonded either to two other carbon atoms or to an aromatic nucleus or a carbon-carbon double bond.
This preparation is referenced from:

References and Notes
  1. Massachusetts Institute of Technology, Cambridge, Massachusetts.
  2. House, J. Am. Chem. Soc., 77, 3070 (1955).
  3. Ramart-Lucas and Salmon-Legagneur, Compt. rend., 186, 1848 (1928).
  4. Henze and Leslie, J. Org. Chem., 15, 901 (1950).
  5. Tiffeneau, Compt. rend., 142, 1537 (1906); Ann. chim. (Paris), [8] 10, 322 (1906).
  6. Stoermer, Ber., 39, 2288 (1906).
  7. Danilov and Venus-Danilova, Ber., 59B, 1032 (1926).
  8. Tiffeneau, Compt. rend., 150, 1181 (1910).
  9. Behal and Sommelet, Bull. soc. chim. France, [3] 31, 300 (1904).
  10. Thomas and Bettzieche, Z. physiol. Chem., 140, 261 (1924).
  11. Sou, Bull. fac. sci. univ. franco-chinoise Peiping, 1935, No. 5, 1 [C. A., 30, 4463 (1936)].
  12. Bersch, Meyer, and Hubner, Pharm. Zentralhalle, 96, 381 (1957) [C. A., 52, 13684 (1958)].
  13. Buttenberg, Ann., 279, 324 (1894).
  14. Brueur and Zincke, Ann., 198, 141 (1879).
  15. Ecary, Ann. chim. (Paris), [12] 3, 445 (1948).
  16. Haarmann & Reimer, Chemische Fabrik zu Holzminden G.m.b.H., Ger. pat. 825,085 [C. A., 49, 11713 (1955)].
  17. Wittig and Knauss, Angew. Chem., 71, 127 (1959).
  18. Klages and Kessler, Ber., 39, 1753 (1906).
  19. Cope, Trumbull, and Trumbull, J. Am. Chem. Soc., 80, 2844 (1958).

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


2,2-dipheny1-2-hydroxyethyl ether


diphenylacetic and formic acid


diphenylacetaldehyde enol methyl ether


cis- or trans-stilbene oxide

sulfuric acid (7664-93-9)

hydrochloric acid (7647-01-0)

Benzene (71-43-2)

acetic anhydride (108-24-7)

Oxalic acid (144-62-7)

sodium bisulfite (7631-90-5)

thorium oxide

carbon (7782-42-5)

Benzophenone (119-61-9)

oxirane (75-21-8)

ethylene (9002-88-4)

Ethyl chloroacetate (105-39-5)

2,4-Dinitrophenylhydrazine (119-26-6)

magnesium sulfate (7487-88-9)


Acetaldehyde, diphenyl- (947-91-1)

boron trifluoride etherate,
boron trifluride etherate (109-63-7)

1,2-dihydroxy-1,2-diphenylethane (52340-78-0)



β,β-diphenylvinyl ethyl ether


lithium diethylamide


trans-Stilbene oxide (1439-07-2)

trans-Stilbene (103-30-0)