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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Sush_eera on June 16, 2016, 10:18:06 PM

Title: Making an azo dye from Benzene
Post by: Sush_eera on June 16, 2016, 10:18:06 PM
Can someone help me with this organic question. i have a chem exam next week. so this is about preparation of methyl red ( an azo compound) from benzene
 so this is what i tried:
1. convert benzene to nitrobenzene by adding HNO3 / conc. H2SO4 at 50oC
2. later, convert the nitro benzene into an amine benzene by adding Sn/CHCl
3. The convert amide Benzene into diazonium salt by adding NaNo3and HCL at 5oC
 
I dont know what to do to form a azo compound after converting the Benzene to a diazonium salt. Can some one help? pleaseee.. This is the question
Title: Re: help
Post by: orgopete on June 16, 2016, 10:28:10 PM
You need to look up how to form the diazo bond. That will suggest the route for the preparation.
Title: Re: help
Post by: Sush_eera on June 16, 2016, 10:31:25 PM
Quote from: orgopete on June 16, 2016, 10:28:10 PM
You need to look up how to form the diazo bond. That will suggest the route for the preparation.
yes I do know how to form a diazonium bond but i cant seem to figur out what happens after the diazonium bond is formed.. like how to get to the sturcture shown in the picture.
Title: Re: Making an azo dye from Benzene
Post by: critzz on June 17, 2016, 06:01:36 AM
If you don't know how to make the azo-functionality, then how do you know you need to make a diazonium compound first?  :P
Anyways, if I remember correctly you can literally find the reaction in Clayden's organic chemistry book (search for a diazo-coupling or diazonium salt).

Quote from: Sush_eera on June 16, 2016, 10:18:06 PM
1. convert benzene to nitrobenzene by adding HNO3 / conc. H2SO4 at 50oC
2. later, convert the nitro benzene into an amine benzene by adding Sn/CHCl
3. The convert amide Benzene into diazonium salt by adding NaNo3and HCL at 5oC

How and when would you introduce the carboxylic acid moiety?



Title: Re: help
Post by: orgopete on June 17, 2016, 07:47:35 AM
Quote from: Sush_eera on June 16, 2016, 10:31:25 PM

yes I do know how to form a diazonium bond but i cant seem to figur out what happens after the diazonium bond is formed.. like how to get to the sturcture shown in the picture.

The route having been suggested gives a "diazonium salt". It can react in a characteristic way to give a diazo bond as shown for the dye. Most textbooks show this. Again, I suggest looking it up. Hint, dimethylaniline is one of the needed reactants.
Title: Re: Making an azo dye from Benzene
Post by: CKabes on June 17, 2016, 10:48:17 PM
1. Make toluene with CH3Cl and AlCl3
2. Nitrate while you still have an o/p director
3. Oxidize the toluene with KMnO4
4. Reduce the amine with SnCl2
5. Make the diazonium salt with NaNO2Cl
6. Couple with dimethylanaline