How quickly\slowly did you add the diazonium salt to the NaI solution?
Did you maintain the reaction temperature below 10°C during the entire addition?
Did you also keep the diazonium salt cooled while adding it?
After addition was complete, did you let the reaction stir at 10°C until nitrogen evolution ceased and then let the reaction slowly warm to room temp?
Here is a tested lab procedure for the preparation of 4-iodonitrobenzene. Compare it to your notes and see where you differed.
Keeping the reaction cold during the addition is key. If the diazonium salt warms up too much, the diazonium can react with itself (coupling) to give colored by-products. The diazonium ion can also eliminate nitrogen to generate the extremely reactive phenyl cation which will react with any nucleophile around, water for example (see page 6, the Mechanism section in this reference). Both pathways can contaminate and reduce the yield of the desired product.
How quickly\slowly did you add the diazonium salt to the NaI solution?
Did you maintain the reaction temperature below 10°C during the entire addition?
Did you also keep the diazonium salt cooled while adding it?
After addition was complete, did you let the reaction stir at 10°C until nitrogen evolution ceased and then let the reaction slowly warm to room temp?
Here is a tested lab procedure for the preparation of 4-iodonitrobenzene. Compare it to your notes and see where you differed.
Keeping the reaction cold during the addition is key. If the diazonium salt warms up too much, the diazonium can react with itself (coupling) to give colored by-products. The diazonium ion can also eliminate nitrogen to generate the extremely reactive phenyl cation which will react with any nucleophile around, water for example (see page 6, the Mechanism section in this reference). Both pathways can contaminate and reduce the yield of the desired product.
). Iodide is reactive enough to react directly with the diazonium ion, bromine and chlorine need a little help from copper. Water is also reactive enough that generating the diazonium ion in the presence of excess water is a standard route to phenols.More
So the benzene ring of the diazonium could react with a Nitrogen triple bond? How could it react with itself? Would the Nitrogen dioxide act as a nucleophile on the nitrogen triple bond?More
Yes, the terminal nitrogen in the diazonium can react with another activated aromatic compound (starting material, final product, by-product) to produce coupling products. Your ring has a nitro group, so it is deactivated and less likely to couple. More likely, your diazonium salt thermally decomposes (eliminates nitrogen) to generate the extremely reactive phenyl cation which will react with any nucleophile around, water for example.More
Here are some things to focus on:
Here is a tested lab procedure for the preparation of 4-iodonitrobenzene. Compare it to your notes and see where you differed.
Keeping the reaction cold during the addition is key. If the diazonium salt warms up too much, the diazonium can react with itself (coupling) to give colored by-products. The diazonium ion can also eliminate nitrogen to generate the extremely reactive phenyl cation which will react with any nucleophile around, water for example (see page 6, the Mechanism section in this reference). Both pathways can contaminate and reduce the yield of the desired product.
Here are some things to focus on:
Here is a tested lab procedure for the preparation of 4-iodonitrobenzene. Compare it to your notes and see where you differed.
Keeping the reaction cold during the addition is key. If the diazonium salt warms up too much, the diazonium can react with itself (coupling) to give colored by-products. The diazonium ion can also eliminate nitrogen to generate the extremely reactive phenyl cation which will react with any nucleophile around, water for example (see page 6, the Mechanism section in this reference). Both pathways can contaminate and reduce the yield of the desired product.
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