Org. Synth. 1940, 20, 57
DOI: 10.15227/orgsyn.020.0057
[Phenol, o-n-heptyl-]
Submitted by R. R. Read and John Wood, Jr..
Checked by W. E. Bachmann and M. C. Kloetzel.
1. Procedure
In a 1-l. three-necked flask fitted with a stirrer (Note 1) and a reflux condenser is placed 200 g. of amalgamated mossy zinc (Note 2). A mixture of 200 ml. of water and 200 ml. of concentrated hydrochloric acid is added and then a solution of 60 g. of o-heptanoyl phenol (Note 3) in 100 ml. of ethanol. The mixture is agitated vigorously and refluxed until reduction is complete (Note 4).
To the mixture is added 120 ml. of toluene, stirring being continued for a few minutes. The toluene solution is separated from the aqueous solution and washed three times with water. The solution is filtered from suspended matter, and the toluene is distilled from a Claisen flask until a thermometer in the liquid reads 170° (Note 5). The residue is then distilled under reduced pressure, the portion boiling at 118–123° at 1 mm. being collected (Note 6). The yield of colorless o-n-heptylphenol is 45–47 g. (81–86%) (Note 7).
2. Notes
1. The stirrer should be as large and substantial as the flask will accommodate, since the rate of reduction depends greatly on complete emulsification of the oil.
2. The zinc is amalgamated in the reaction flask by covering it with a solution of 4 g. of mercuric chloride in 300 ml. of water. Occasional agitation during 30 minutes is sufficient for amalgamation. The solution is poured off, and the zinc is rinsed once with water.
3. o-Heptanoyl phenol may be prepared by the method of Miller and Hartung [Org. Syntheses Coll. Vol. 2, 543 (1943)]. The checkers found that, by keeping the mixture of ortho and para isomers in a cool place overnight, most of the para isomer crystallized and could be separated by filtration. The ortho isomer is then obtained by fractional vacuum distillation, repeated two or three times. o-Heptanoylphenol boils at 135–140°/3 mm.; p-heptanoyl phenol boils at 200–207°/4 mm.
4. The reduction requires at least 8 hours and may take twice that long. For testing completeness of reduction, 0.1 ml. of the oil is withdrawn and dissolved in 2 ml. of ethanol; to the solution is added 2–4 drops of a 10% solution of ferric chloride in ethanol. A deep red or reddish brown color is produced by the ketone; a light brownish yellow color indicates completion of the reduction. A standard solution containing 0.5 g. of the ketone per liter of ethanol is used for comparison, 2 ml. of this being treated with a few drops of the ferric chloride solution. Since the para acylphenols usually do not give a pronounced color with ferric chloride, at least 8 hours should be allowed for their reduction.
5. Drying of the toluene extract is unnecessary, since the water is carried over during the removal of the toluene. If necessary, the toluene may be returned once to the flask to effect complete removal of the water.
6. The residue from the distillation is usually less than 5 g. and may be discarded.
7. Other ketones may be reduced by this same procedure. The submitters report that the following have been reduced with yields of 70–90%: o- and p-butyryl phenols, o- and p-valeryl phenols, o- and p-caproyl phenols, o- and p-heptanoyl phenols, o- and p-octanoyl phenols, o- and p-pelargonyl phenols, o- and p-undecylyl phenols. The same procedure applies to acyl resorcinols and acyl chlororesorcinols. Caproyl and octanoyl resorcinols reduce to the corresponding alkyl derivatives in yields of 70–80%. Butyryl, valeryl, caproyl, heptanoyl, and octanoyl chlororesorcinols reduce to the corresponding alkyl chlororesorcinols in yields of 60–75%.
3. Discussion
Primary alkyl phenols have been prepared by the reduction of acyl phenols;1 by the demethylation of the corresponding ethers;1,2 by the diazotization of the corresponding amines;3 and by the alkali fusion of sulfonates.4 Alkyl resorcinols have been prepared by the reduction of acyl resorcinols.1,5,6 Alkyl chlororesorcinols have been prepared from the corresponding acyl chlororesorcinols by reduction.7

References and Notes
  1. Johnson and Hodge, J. Am. Chem. Soc., 35, 1014 (1913); Coulthard, Marshall, and Pyman, J. Chem. Soc., 1930, 280.
  2. Klages, Ber., 32, 1438 (1899).
  3. Org. Syntheses Coll. Vol. 1, 128, 407 (1941).
  4. Ullmann, Enzykolpädie der technischen Chemie, Vol. 9, p. 35, Urban and Schwarzenberg, Berlin, 1921.
  5. Johnson and Lane, J. Am. Chem. Soc., 43, 348 (1921).
  6. Dohme, Cox, and Miller, J. Am. Chem. Soc., 48, 1688 (1926).
  7. Read, Reddish, and Burlingame, J. Am. Chem. Soc., 56, 1377 (1934).

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

butyryl phenols

o- and p-valeryl phenols

o- and p-caproyl phenols

o- and p-heptanoyl phenols

o- and p-octanoyl phenols

o- and p-pelargonyl phenols

o- and p-undecylyl phenols

ethanol (64-17-5)

hydrochloric acid (7647-01-0)

toluene (108-88-3)

zinc (7440-66-6)

mercuric chloride (7487-94-7)

ferric chloride (7705-08-0)

Phenol, o-n-heptyl- (5284-22-0)

o-heptanoyl phenol,

p-heptanoyl phenol