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 Purification of Aniline
  • Purification of Aniline
  • Aniline (CAS NO. 62-53-3) is hygroscopic. It can be dried with KOH or CaH2, and distd at reduced pressure. Treatment with stannous chloride removes sulfur-containing impurities, reducing the tendency to become coloured by aerial oxidn. Can be crystd from Et2O at low temps. More extensive purifications involve preparation of derivatives, such as the double salt of aniline hydrochloride and cuprous chloride or zinc chloride, or N-acetylaniline (m 114 °C) which can be recrystd from water.

    Recrystd aniline was dropped slowly into an aqueous soln of recrystd oxalic acid. Aniline oxalate was filtered off, washed several times with water and recrystd three times from 95 % EtOH. Treatment with satd Na2CO3 soln, regenerated aniline which was distd from the soln, dried and redistd under reduced pressure.

    After refluxing with 10 % acetone for 10 h, aniline was acidified with HCl (Congo Red as indicator) and extracted with Et2O until colourless. The hydrochloride was purified by repeated crystn before aniline was liberated by addition of alkali, then dried with solid KOH, and distd. The product was sulfur-free and remained colourless in air.

    Non-basic materials, including nitro compounds were removed from aniline in 40 % H2SO4 by passing steam through the soln for 1 h. Pellets of KOH were added to liberate the aniline which was steam distd, dried with KOH, distd twice from zinc dust at 20mm, dried with freshly prepared BaO, and finally distd from BaO in an all-glass apparatus. Aniline is absorbed by skin and is toxic.

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