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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Steenrod on November 13, 2012, 02:01:26 PM

Title: Separation of mixture
Post by: Steenrod on November 13, 2012, 02:01:26 PM: How would you completely separate the ingredients of a mixture of aniline and nitrobenzene?

Thanks.
Title: Re: Separation of mixture
Post by: discodermolide on November 13, 2012, 02:07:05 PM: What features of the two molecules could help you do this?
Hint: nitro group and amino group, what are their properties?
Title: Re: Separation of mixture
Post by: Steenrod on November 13, 2012, 02:12:32 PM: Sorry,i am lost here
Title: Re: Separation of mixture
Post by: discodermolide on November 13, 2012, 02:14:29 PM: Well forum rules insist you show your efforts at a solution.
Title: Re: Separation of mixture
Post by: Steenrod on November 13, 2012, 02:16:22 PM: Sorry, working 18 hours a day is too much.I am going off to sleep,I shall try it next morning.

I doubt if I know any property by which these two can be distinguished.
Title: Re: Separation of mixture
Post by: orgopete on November 13, 2012, 05:55:26 PM: Hint, one of these can be made to dissolve in water. Check a pKa table.
Title: Re: Separation of mixture
Post by: Steenrod on November 15, 2012, 12:23:16 PM: Ok, I read stuff up and came up with this:

Aniline dissolves in dil HCl with this reaction:

[itex]C_6H_5NH_2+HCl\rightarrow C_6H_5NH_3^{+}Cl^{-}[/itex]

Nitrobenzene does not dissolve in it but forms the bottom layer in the mixture,so the upper layer can be separated out.

But what next?Am I on the right track?
(and what happens when phenol is also present in the same mixture?)
Title: Re: Separation of mixture
Post by: discodermolide on November 15, 2012, 03:03:55 PM: Yes, well done you are there, you have separated your mixture.
Phenol will not be soluble in the dilute acid and may come out with the nitrobenzene, so how would you separate that pair?
Title: Re: Separation of mixture
Post by: Steenrod on November 15, 2012, 10:31:56 PM: I don't know how to separate them.

I was thinking about the Ferric chloride test where phenol turns deep violet but that does not seem useful here.Can you please tell me how to proceed from this point?
Title: Re: Separation of mixture
Post by: discodermolide on November 15, 2012, 11:49:46 PM: What properties of phenol do you know:
Hint: Think the opposite of aniline.
Title: Re: Separation of mixture
Post by: Steenrod on November 16, 2012, 06:06:42 AM: I cannot think of anything else.What can be the possible answer?

Are you hinting at using Dilute NaOH? Won't phenol react with dil NaOH to form sodium phenoxide,a colourless solution, which when treated with dilute HCl gives back phenol?

I do not have much information about nitrobenzene;my text has only 1 page on it and mentions nothing about reacting with dil NaOH.
Title: Re: Separation of mixture
Post by: discodermolide on November 16, 2012, 06:52:22 AM: Yes adding NaOH solution will separate the phenol from the nitrobenzene .
Title: Re: Separation of mixture
Post by: zhangcarlin on November 16, 2012, 06:21:02 PM: Quote from: discodermolide on November 16, 2012, 06:52:22 AM
Yes adding NaOH solution will separate the phenol from the nitrobenzene .

You are a good teacher