(Hive Bee)
07-28-02 19:10
No 338090
      Aniline syntheses
(Rated as: excellent)

Here are another two aniline syntheses.

The first one is similar to the one on Rhodium's page. It is taken from

Method 1

Prepare a mixture of 90g of tin granules and 41.5mL of nitrobenzene in a 1000mL RB flask. Gradually add about 17mL of concentrated HCl, attach a reflux condenser, with or without water flowing, and shake the flask until thoroughly mixed. The flask will become warm after a short time, and a vigorous reaction can be observed. When this happens, immerse the flask in cold water to moderate the reaction. Add another 17mL of HCl and repeat the shaking/cooling process. Add a third and fourth portion of acid until approximately 80-85mL of acid has been added, shaking and cooling each time. At this point the addition of acid should not give as quite a violent reaction, add an additional 85-90mL of HCl in larger portions. The total amount of acid added is 167 mL.
After all of the acid has been added, the mixture is heated on a steam bath for 1 hour at reflux. After refluxing, add 100mL of water to the flask. Prepare a solution of 150g of sodium hydroxide in 200mL water, gradually add this solution to the flask in small portions. If the addition of the hydroxide solution causes the contents of the flask to boil, cool the flask in a water bath before adding more.
To distill the aniline, set the flask up for steam distillation and distill, aniline and water will be collected. The initial distillate will be a milky color, when it becomes clear remove the collecting flask and add a new one. Collect an additional 300mL of distillate.

Combine the two distillate portions in an Erlenmeyer flask, and then add 25g of finely powdered sodium chloride for every 100mL of distillate collected. Shake the flask until all of the salt dissolves, then extract the solution with several portions of ether. Combine the ether portions, add a small amount of potassium hydroxide, and allow the ether to evaporate. The crude aniline thus obtained can be purified by simple distillation. The yield is 90-100%.

Method 2

12.3g (10.25mL) of nitrobenzene is dissolved in 70mL EtOH. To this solution is added 1.5g 5% Pd/C and the flask is connected to the hydrogenator. The apparatus is filled with 10L H2 and the mixture is stirred for 15 hours with a magnetic stirrer. After 15h the Pd/C is filtered off with suction and EtOH is evaporated on rotavap. The oily residue is redistilled, yielding pure aniline (bp 184 C)

Reference: D. J. Cram, G. S. Hammond, J. B. Hendrickson, Organic Chemistry, 3rd eddition, 1970

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