how we can select catalyst, actually i want to replace acetamide by another catalyst in my acid chloride synthesis reaction.
Dimethylformamide has always worked well for me. Others use N-methylimidazole or 4-(dimethylamino)pyridine. If the reagents are cheap or easily prepared, you might just try screening a few catalysts to see which works best. Which chlorinating agent are you using?
i am using thionyl chloride and dicarboxylic acid for acid chloride synthesis. after that i want to synthesize polyamide by using that acid chloride and diamine.
actually my acid chloride is ready but now my diamine is not reacting reacting.
what to do for that?
hard to know what is going wrong, but I have a few guesses:
1) Depending on how you worked up the acid chloride, there might be a significant amount of HCl (or SOCl2) left over. If you haven't added enough amine (or other base), it could all have converted into the ammonium chloride, which will not react.
2) If there is a significant amount of water contamination, this could react with the acid chloride (typically not a very fast side reaction, but this depends on how much water there is). Resulting in both less acid chloride, and more HCl, which would then deactivate some of the amine.
3) Depending on the shape and flexibility of the amine and or acyl chloride, it could be that the reaction preferentially forms cyclic dimers (one diamine and one diacid) or low MW oligomers...
4) There could be steric hinderance on one or both of the coupling partners.
5) One or both of the coupling partners may have poor solubility.
...
For the acyl chloride synthesis make sure you: use
- use fresh SOCl2 (this is a hygroscopic substance that hydrolyzes);
- distil the unreacted SOCl2.
For the amine:
- use freshly distil reagent (without brown impurities);
- keep in brown recipients in the dark and low temperature.
Run the reaction in clean and dry glassware and use a trap for the HCl.
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