Quiz5A - 1 CHM 2123, Quiz #5: Reduction of Nitrobenzene...

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1 CHM 2123, Quiz #5: Reduction of Nitrobenzene Assigned: October 19th, 2006 Due: October 23, 2006, before 5 pm MARKING SCHEME 1. Isolation of aniline by steam distillation. a) Why is NaOH added before performing the distillation? (1 point) b) Suggest a reason for the milky appearance of the distillate and for the change in appearance upon addition of HCl. (1 point) a) As the reaction is carried out under acidic conditions, protonated aniline is obtained. The anilinium chloride is a salt and therefore not volatile. It needs to be neutralized before it could be distilled. b) Aniline is an organic compound and is probably non-miscible with water. The milky appearance is probably due to an emulsion. When HCl is added, the water-soluble anilinium chloride is formed, and the milky colour dissipates. 2. After having isolated the reduction product, aniline, a reaction is performed using acetic anhydride in which a precipitate is formed. What is this precipitate? Why does precipitation occur as the reaction progresses? (2 points)
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Quiz5A - 1 CHM 2123, Quiz #5: Reduction of Nitrobenzene...

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