3cmc in ethyl acetate

[orze.ch311]

Hey guys,

I have made some 3cmc in ethyl acetate and yield was below 20%. I used 100g 2b3c, 200ml ethyl acetate and 200ml methyloamine. Now I'm looking for my mistake and I think the problem is in amination process. How long should amination lasts? Color of solution is any signal that I must stop? How could reacts my product when I let amination for 3 or more hours?

 

[AgamemnonFromTroy]

Hello,
One indicator that can tell you the amination of 2-Bromo-3'-chloropropiophenone in ethylacetate with Methylamine (in the form of 40% solution in H2O) is completed is the change in colour from usually milky-white(after methylamine was added) to a pale-yellow. If the colour of the reaction mixture turns orange or red it could indicate the formation of imines, amine oxidation, degradation of substrate/product. After you notice the yellow tint staring to appear you should look for further changes in the color(it getting paler or more opaque) if the colour remains the same for quite some time (around 2-3 hours given the scale ) reaction should be done. Leaving it too much can lead to over amination and not leaving it for enough time could lead to having a final product contaminated with the bromo ketone.
It's also important to consider that the reaction itself is the easiest part that most people get right but the workup can severely impact yields if not done properly.