Org. Synth. 1926, 6, 16
DOI: 10.15227/orgsyn.006.0016
m-BROMOTOLUENE
[Toluene, m-bromo-]
Submitted by L. A. Bigelow, J. R. Johnson, and L. T. Sandborn.
Checked by Frank C. Whitmore and A. M. Griswold.
1. Procedure
To a cold mixture of
800 cc. of 95 per cent ethyl alcohol and 200 cc. of concentrated sulfuric acid (Note 1) in a
5-l. round-bottomed flask, provided with an
efficient mechanical stirrer, is added
250 g. (1.33 moles) of crude 3-bromo-4-aminotoluene (p. 111). The solution is stirred and cooled to 10°, and a solution of
148 g. (2.05 moles) of u.s.p. sodium nitrite in 260 cc. of water is added from a
separatory funnel. During this addition, the temperature of the mixture must not be allowed to rise above 10°. After all of the
nitrite solution has been added, the mixture is stirred twenty minutes longer to complete the diazotization.
To the diazotized solution is added 35 g. (0.55 atom) of copper bronze (Note 2) which has been washed with ether. The stirrer is replaced by a long, efficient reflux condenser. A bath of ice water is prepared for cooling the flask when the reaction becomes too vigorous. The flask is warmed cautiously until a vigorous evolution of gas starts. It is then immersed in the ice water to prevent loss through the condenser by too rapid evolution of nitrogen and acetaldehyde. When the reaction has moderated, the flask is again warmed, and finally the mixture is heated for ten minutes on a steam bath. At the end of the reaction the color changes from reddish brown to yellow.
After the addition of 2 l. of water, the mixture is steam-distilled as long as any oil comes over. The crude, heavy, yellow oil is separated and washed with two
200-cc. portions of 10 per cent sodium hydroxide, once with 100 cc. of water, twice with
150-cc. portions of concentrated sulfuric acid, and finally with
100 cc. of 5 per cent sodium carbonate solution. It is dried with about
5 g. of calcium chloride, filtered through
glass wool, and distilled using a
long air condenser. Most of the product boils at
180–183°/750 mm. The yield of pure colorless material, b.p.
183°/760 mm., is
125–135 g. (
36–39 per cent of the theoretical amount, based on the amount of
p-toluidine originally used
(p. 111), or
54–59 per cent based on the amount of
3-bromo-4-aminotoluene).
2. Notes
1.
Proper care must be exercised in mixing the
alcohol and
sulfuric acid. The mixture is best cooled in the flask with stirring.
2.
Reduced
copper powder and various grades of
copper bronze were used with practically the same results.
3. Discussion
m-Bromotoluene can be prepared by the diazotization of
m-toluidine followed by treatment with
cuprous bromide,
potassium bromide and
hydrobromic acid,
1 and by elimination of the amino group from
3-bromo-4-aminotoluene2 and
5-bromo-2-aminotoluene.
3 The procedure described is a modification of the method of Feitler.
2
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
copper bronze
ethyl alcohol,
alcohol (64-17-5)
calcium chloride (10043-52-4)
acetaldehyde (75-07-0)
sulfuric acid (7664-93-9)
ether (60-29-7)
sodium hydroxide (1310-73-2)
HYDROBROMIC ACID (10035-10-6)
sodium carbonate (497-19-8)
nitrogen (7727-37-9)
sodium nitrite (7632-00-0)
nitrite (14797-65-0)
copper powder (7440-50-8)
3-Bromo-4-aminotoluene (583-68-6)
potassium bromide (7758-02-3)
cuprous bromide (7787-70-4)
5-bromo-2-aminotoluene (583-75-5)
p-toluidine (106-49-0)
m-toluidine (108-44-1)
m-Bromotoluene,
Toluene, m-bromo- (591-17-3)
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