A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1938, 18, 61
DOI: 10.15227/orgsyn.018.0061
[Benzaldehyde, p-nitro-]
Submitted by S. V. Lieberman and Ralph Connor.
Checked by John R. Johnson and E. A. Cleveland.
1. Procedure
(A) p-Nitrobenzaldiacetate.—In a 2-l. three-necked, round-bottomed flask equipped with a mechanical stirrer and a thermometer, and surrounded by an ice-salt bath, are placed 570 cc. (600 g.) of glacial acetic acid, 565 cc. (612 g., 6 moles) of acetic anhydride (Note 1), and 50 g. (0.36 mole) of p-nitrotoluene (Note 2). To this solution is added slowly, with stirring, 85 cc. (1.5 moles) of concentrated sulfuric acid (Note 3). When the mixture has cooled to 5°, 100 g. (1 mole) of chromium trioxide (Note 2) is added in small portions at such a rate that the temperature does not rise above 10° (Note 4), and stirring is continued for ten minutes after the chromium trioxide has been added. The contents of the flask are poured into two 3-l. beakers two-thirds filled with chipped ice, and cold water is added until the total volume is 5–6 l. The solid is separated by suction filtration and washed with cold water until the washings are colorless. The product is suspended in 500 cc. of cold 2 per cent sodium carbonate solution and stirred mechanically. After thorough mixing, the solid is collected on a filter (Note 5) and washed with cold water and finally with 20 cc. of cold alcohol. The product, after drying in a vacuum desiccator, weighs 44–49 g. (48–54 per cent of the theoretical amount), m.p. 120–122° (Note 6).
The crude material is suitable for hydrolysis, and for other reactions, without further purification. The pure diacetate may be obtained by recrystallizing from 150 cc. of hot alcohol. The hot solution is filtered through a fluted filter to remove insoluble impurities. The yield of pure p-nitrobenzaldiacetate is 43–46 g. (47–50 per cent of the theoretical amount), m.p. 125–126°.
(B) p-Nitrobenzaldehyde.—A mixture of 45 g. (0.18 mole) of crude p-nitrobenzaldiacetate, 100 cc. of water, 100 cc. of alcohol, and 10 cc. of concentrated sulfuric acid is refluxed for thirty minutes and filtered through a fluted filter, and the filtrate is chilled in an ice bath. The crystals are separated by suction filtration, washed with cold water, and dried in a vacuum desiccator. The first crop weighs 22–24 g. (82–89 per cent of the theoretical amount), m.p. 106–106.5°. A second crop amounting to 2–3 g. is obtained by diluting the filtrate with about 300 cc. of water. The total yield is 24–25.5 g. (89–94 per cent of the theoretical amount) (Note 6).
2. Notes
1. The "practical" grade of acetic anhydride (95 per cent) gave yields as high as those obtained with 99–100 per cent acetic anhydride.
2. The p-nitrotoluene used was a "practical" grade, m.p. 50–51°. The chromium trioxide was a u.s.p. grade of 98 per cent purity.
3. If the sulfuric acid is added too rapidly, charring occurs.
4. It is essential that the temperature of the reaction mixture be maintained below 10°. If the oxidant is added so rapidly that this temperature is exceeded, the yield is lowered considerably. With a good ice-salt bath, the time required for the addition is forty-five to sixty minutes.
5. By acidification of the sodium carbonate washings, 7–10 g. of p-nitrobenzoic acid, m.p. 242–243°, is obtained.
6. This procedure appears to be generally applicable to the preparation of those substituted benzaldehydes in which the substituent is not attacked in the oxidation reaction. Thus, the submitters report that p-bromobenzaldehyde may be prepared by the same procedure, substituting 62 g. (0.37 mole) of p-bromotoluene for the p-nitrotoluene and carrying out the oxidation and isolation in the same manner. The yield of crude p-bromobenzaldiacetate is 51–64 g. (48–60 per cent of the theoretical amount), m.p. 90–92°. The pure diacetate is obtained by dissolving the crude product in 150 cc. of hot alcohol, filtering through a fluted filter, and cooling. Filtration gives 39–52 g. of pure material, m.p. 94–95°. A second crop is obtained by diluting the filtrate. The total yield is 47–56 g. (46–54 per cent of the theoretical amount, based on the bromotoluene). The crude product is hydrolyzed to p-bromobenzaldehyde by refluxing 45 g. (0.157 mole) with 100 cc. of water, 150 cc. of alcohol, and 10 cc. of concentrated sulfuric acid, filtering through a fluted filter, cooling, and filtering with suction. A second crop is obtained by diluting the filtrate with about 300 cc. of water. The product weighs 24–28 g. (83–96 per cent of the theoretical amount), m.p. 55–57°.
It is further reported that p-cyanotoluene furnishes p-cyanobenzaldehyde, the yield being about the same as that in the preparation of p-nitrobenzaldehyde. (Leonard Weisler, private communication.)
3. Discussion
p-Nitrobenzaldehyde has been prepared from p-nitrotoluene by treatment with isoamyl nitrite in the presence of sodium methoxide1 or by oxidation with chromyl chloride,2 cerium dioxide,3 or chromium trioxide in the presence of acetic anhydride.4 It can also be prepared by the oxidation of p-nitrobenzyl chloride,5 p-nitrobenzyl alcohol,6 or the esters of p-nitrocinnamic acid.7

References and Notes
  1. Angeli and Angelico, Atti accad. Lincei (5) 8, II, 28 (1899) (Chem. Zentr. 1899, II, 371).
  2. Richter, Ber. 19, 1060 (1886); Law and Perkin, J. Chem. Soc. 93, 1635 (1908).
  3. Farbw. vorm. Meister, Lucius, and Brüning, Ger. pat. 174,238 [Frdl. 8, 150 (1905–07)].
  4. Thiele and Winter, Ann. 311, 353 (1900).
  5. Fischer and Greiff, Ber. 13, 669 (1880); Schmidt, Ger. pat. 15,881 [Frdl. 1, 60 (1877–87)].
  6. Cohen and Harrison, J. Chem. Soc. 71, 1057 (1897); Walter, Ger. pat. 118,567 [Frdl. 6, 131 (1900–02)].
  7. Baeyer, Ger. pat. 15,743 [Frdl. 1, 60 (1877–87)].

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

alcohol (64-17-5)

sulfuric acid (7664-93-9)

acetic acid (64-19-7)

acetic anhydride (108-24-7)

sodium carbonate (497-19-8)

sodium methoxide (124-41-4)

p-cyanotoluene (104-85-8)

chromyl chloride

chromium trioxide (1333-82-0)

Isoamyl nitrite (110-46-3)

p-Nitrobenzaldiacetate (2929-91-1)

Benzaldehyde, p-nitro- (555-16-8)

bromotoluene (95-46-5)

cerium dioxide


p-Bromotoluene (106-38-7)

p-Nitrobenzyl alcohol (619-73-8)

p-Bromobenzaldehyde (1122-91-4)

p-nitrotoluene (99-99-0)

p-bromobenzaldiacetate (55605-27-1)

p-cyanobenzaldehyde (105-07-7)

p-nitrobenzyl chloride (100-14-1)

esters of p-nitrocinnamic acid (619-89-6)