A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1940, 20, 18
DOI: 10.15227/orgsyn.020.0018
[2-Naphthol, 6-bromo-]
Submitted by C. Frederick Koelsch
Checked by W. E. Bachmann and S. Kushner.
1. Procedure
In a 3-l. round-bottomed flask fitted with a dropping funnel and a reflux condenser (Note 1) are placed 144 g. (1 mole) of β-naphthol and 400 ml. of glacial acetic acid. Through the dropping funnel is then added a solution of 320 g. (2 moles) of bromine in 100 ml. of acetic acid. The flask is shaken gently during the addition, which requires 15–30 minutes. The β-naphthol dissolves during this period, and heat is evolved; the mixture is cooled somewhat towards the end of the addition to avoid excessive loss of hydrogen bromide. One hundred milliliters of water is then added, and the mixture is heated to boiling. It is then cooled to 100°, 25 g. of mossy tin is added (Note 2), and boiling is continued until the metal is dissolved. A second portion of 25 g. of tin is then added and dissolved by boiling, and finally a third portion of 100 g. (a total of 150 g., 1.27 gram atoms) of tin is introduced. The mixture is boiled for 3 hours, cooled to 50°, and filtered with suction. The crystalline tin salts which are thus removed are washed on the funnel with 100 ml. of cold acetic acid, the washings being added to the main portion of the filtrate.
This filtrate is stirred into 3 l. of cold water; the 6-bromo-2-naphthol which is precipitated is filtered with suction, removed from the funnel, and washed by stirring with 1 l. of cold water. After filtering again and drying at 100° there is obtained 214–223 g. (96–100%) of 6-bromo-2-naphthol. This crude product, which is pink and melts at 123–127°, contains some tin but is pure enough for most purposes.
A white product is obtained by vacuum distillation followed by crystallization of the crude product. Twenty-five grams of the crude substance on distillation (Note 3) gives 20 to 24 g. of distillate boiling at 200–205°/20 mm., and when this is crystallized from a mixture of 75 ml. of acetic acid and 150 ml. of water it gives 17.5 to 22.5 g. of 6-bromo-2-naphthol which melts at 127–129°.
2. Notes
1. An all-glass apparatus is of considerable advantage. If this is not available, the cork is covered with lead foil.
2. The reflux condenser is removed in order to add the tin, but it should be held in readiness so that it can be replaced quickly. The first two portions of tin react vigorously, and solution of the metal is accompanied by the evolution of hydrogen and the loss of some hydrogen bromide.
3. For the distillation a sausage flask or two-bulb flask1 (Fig. 6) is employed.
Fig. 6.
Fig. 6.
3. Discussion
6-Bromo-2-naphthol has been prepared by the reduction of 1,6-dibromo-2-naphthol with hydriodic acid,2 with tin and hydrochloric acid,3 or with stannous chloride and hydrochloric acid in aqueous alcohol3 or in aqueous acetic acid.4 It has also been obtained by the bromination of 2-naphthol with pyridinium bromide perbromide.5

References and Notes
  1. Fieser, Experiments in Organic Chemistry, p. 246, D. C. Heath & Company, Boston, 1935.
  2. Armstrong, Chem. News, 74, 302 (1897).
  3. Franzen and Staubel, J. prakt. Chem., (2) 103, 369 (1922); Fries and Schimmelschmidt, Ber., 58, 2840 (1925).
  4. Fries and Schimmelschmidt, Ann., 484, 293 (1930).
  5. Vona and Merker, J. Org. Chem., 14, 1048 (1949).

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

pyridinium bromide perbromide

hydrochloric acid (7647-01-0)

acetic acid (64-19-7)

hydrogen (1333-74-0)

hydrogen bromide (10035-10-6)

bromine (7726-95-6)

2-naphthol (135-19-3)

tin (7440-31-5)

stannous chloride

hydriodic acid (10034-85-2)

2-Naphthol, 6-bromo- (15231-91-1)

1,6-dibromo-2-naphthol (16239-18-2)