Org. Synth. 1954, 34, 100
DOI: 10.15227/orgsyn.034.0100
[o-Xylene, α,α'-dibromo-]
Submitted by Emily F. M. Stephenson1
Checked by William S. Johnson, C. W. Taylor, and William DeAcetis.
1. Procedure
Caution! o-Xylylene dibromide is a powerful and persistent lachrymator. The preparation and all subsequent handling of this substance should, therefore, be carried out in an efficient hood with adequate protection by rubber gloves. A gas mask should be at hand for emergency. All apparatus coming in contact with the dibromide should be immersed in alcoholic alkali contained in a large crock with a lid. A period of 24 hours is sufficient for decontamination. Waste substances such as filter paper and corks usually require several days of such soaking before they can be safely discarded.
A 1-l. three-necked round-bottomed flask is fitted with a rubber slip-sleeve-sealed stirrer, a dropping funnel with the tip extended to reach almost to the bottom of the flask (Note 1), and an efficient condenser leading to a gas absorption trap.2 o-Xylene (106 g., 1 mole) (Note 2) is placed in the flask, which is heated with an oil bath and illuminated with a sun lamp (Note 3) placed 1–5 cm. from the upper portion of the flask. When the temperature of the o-xylene reaches 125°, the dropwise addition of 352 g. (2.2 moles) of bromine is commenced with stirring. The rate of addition is regulated so that all the bromine is introduced in 1.5 hours. The mixture is stirred at 125° under illumination for an additional 30 minutes. It is then allowed to cool to 60° and poured into 100 ml. of boiling 60–68° petroleum ether contained in a beaker, the transfer being assisted with small amounts of warm solvent. As the homogeneous solution cools slowly to room temperature it is stirred frequently to prevent caking of the brown crystalline product that separates. After the mixture is cool and the bulk of the dibromide has crystallized, the beaker is placed in a refrigerator for 12 hours (Note 4). The product is then separated by suction filtration, washed twice with 25-ml. portions of cold petroleum ether, and then pressed on the filter until nearly dry. Final drying is effected in a vacuum desiccator containing solid potassium hydroxide. The brown crystalline product amounts to 123–140 g. (48–53% yield), the melting point ranging between 89° and 94° (Note 5).
2. Notes
1. It is convenient to seal a short inner tube inside the stem of the dropping funnel so that the rate of addition can be observed readily. The introduction of the bromine below the surface of the o-xylene through an extended stem, about 4-mm. inside diameter, results in better mixing of reactants and less loss of bromine vapors.
2. The submitter used o-xylene obtained from Light and Company, Wraysbury, Middlesex, England. It was refluxed with sodium, then distilled from sodium, b.p. 144–144.5°, and stored over sodium.
The checkers employed the white label grade of o-xylene supplied by Eastman Kodak Company without further purification.
3. The submitter employed a 600-watt lamp, and the checkers used a 275-watt General Electric sun lamp.
4. Occasional stirring during the first 3–4 hours of this chilling period helps to prevent caking of the product on the side of the beaker.
5. This product is satisfactory for most preparative work. Further purification may be effected by recrystallization from 95% ethanol (3 ml./g.), to give material melting at 93–94° in 80–85% recovery. Other solvents that have been used for recrystallization are petroleum ether (British Drug House, "Analar," b.p. 60–80°) (19 ml./g.), and chloroform (1 ml./g.).
3. Discussion
o-Xylylene dibromide has been prepared from o-xylene by direct bromination3 or by treatment with N-bromosuccinimide;4 by the direct bromination of o-xylyl bromide;5 and by the action of concentrated hydrobromic acid on the monophenyl ether of α,α'-dihydroxy-o-xylene.6 The present procedure is essentially that of Perkin3 as modified by Cope and Fenton.7
This preparation is referenced from:

References and Notes
  1. University of Melbourne, Melbourne, Australia.
  2. Org. Syntheses Coll. Vol. 2, 4 (1943).
  3. Perkin, J. Chem. Soc., 1888, 5; Atkinson and Thorpe, J. Chem. Soc., 1907, 1695.
  4. Wenner, J. Org. Chem., 17, 523 (1952).
  5. von Braun and Cahn, Ann., 436, 262 (1924).
  6. von Braun and Zobel, Ber., 56, 2142 (1923).
  7. Cope and Fenton, J. Am. Chem. Soc., 73, 1668 (1951).

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

petroleum ether

ethanol (64-17-5)

chloroform (67-66-3)


bromine (7726-95-6)

potassium hydroxide (1310-58-3)

sodium (13966-32-0)

monophenyl ether (101-84-8)

N-bromosuccinimide (128-08-5)

o-Xylylene dibromide,
o-Xylene, α,α'-dibromo- (91-13-4)

α,α'-dihydroxy-o-xylene (612-14-6)

o-Xylene (95-47-6)

o-xylyl bromide (576-23-8)