Purifying 2-bromo-4-methylpropiophenone

SonicNL

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Hi

I found a suplier which sells me really good 2bk4.

But, I want to make sure I wash all impurities out before proceeding to 4-MMC synthesis.

How do I do this? The main thing i'm concerned about is 4mpf and bromine. Maybe it isnt neccessary, but I want to purify it anyway

Have a good day!
 
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Do you want to purge the 2b4mp you bought? First you need to make sure it is necessary.
What's wrong with your 2b4mp?
Maybe it has a bad color and texture? Or does it give low yields?
 

SonicNL

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Its seems to be pure color and texture are good AFAIK.

I just want to make sure I use bk as pure as possible.

I followed ur threads regarding synthesis in DCM and purification, but without expected results.
 

SonicNL

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During bromination, in addition to 2BK4, hydrobromic acid (HBr) and other substances were released, contaminating 2BK4. To remove all impurities from the solution, you need to perform several washes with a solution of baking soda and one wash with clean water. Baking soda neutralizes acid, and water rinses away dirt. 2BK4 is insoluble in water, so it remains in DCM (dichloromethane).

Prepare the solution: 100 g of baking soda per 1000 ml of distilled water. Take an empty 2-liter bottle, pour 1000 ml of water into it, and add 100 g of baking soda. Shake vigorously for 2-3 minutes, then let the remaining soda settle for another 2-3 minutes. The solution is ready; do not disturb the settled soda while draining.

Remove everything from the flask: transition, fridge, dropping funnel, and core.

Smoothly (slowly, in small portions), pour approximately 300 ml of the soda solution into our reaction mixture, close the lid, and turn the mixer on for a maximum of 2 minutes. The mixture should become lighter. It will bubble, hiss, and foam – this is the soda neutralizing the acid and bromine. The reaction is active, so add slowly.

Remove the anchor with the anchor extractor. Then vigorously shake with your hands for another 2 minutes (no stirrer can mix as well as you can with your hands in this case, it is important).
Next, set up a separating funnel on a stand and pour out everything in the flask.

Observe how the layers separate (it takes about 30 seconds). The top layer will be aqueous, and the bottom layer will be the 2BK4 solution in DCM.

Once the layers have separated, take an indicator paper and place a small drop of the bottom layer on it, just enough to moisten the paper. The desired color is neutral (yellow, where the paper gets wet but doesn't change color). If it was slightly alkaline, add a drop of soda solution. If it is acidic, repeat the phase by washing with baking soda, letting the bottom layer flow into the flask, and discarding the top layer. This is a crucial step – we need to neutralize all the acid with a soda solution. If you send an underwashed solution to the synthesis, you will likely ruin the batch.

So now there are two layers in the separating funnel. Let the bottom layer (most likely, after 2-3-4 washes with soda, you'll finally see a neutral color) flow into a bottle, and discard the top layer. At this stage, you can collect a small amount of the water layer without losing the 2BK4 layer.

To make it easier to transfer the bottom layer from the funnel directly into the flask, place a stand with the separating funnel on the edge of the table and move the supports aside (CAUTION, THE FUNNEL CAN HANG, FALL, AND BREAK – IT WILL BE VERY DIFFICULT TO CLEAN!). Alternatively, simply hold the funnel in your hands.

Once we finish washing with soda, wash again with clean distilled water: add 100-150 ml of distilled water to the flask, shake vigorously for 2-3 minutes, and pour into a separating funnel. Once again, let the bottom layer flow into the flask and discard the top layer.

Therefore, we have washed with alkali (1-4 times) and pure water (1 time) to remove unreacted bromine, acid, and other by-products, resulting in a pure solution of 2BK4 in DCM.

Cheers
 
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So, was 2b4mp washed of impurities?
The fact is that a similar washing is done at the end of 4mmc synthesis, removing the same impurities.
In production, 2b4mp is washed after bromination. If you have 2b4mp powder, you need to make it liquid again to wash out the impurities.
This can be done by heating it to its melting point (~75-77ºC). But 2b4mp is a strong lacrimator, and that's terrible.
Or you can use solvents. Dissolving in glacial acetic acid followed by precipitation in water and washing with sodium bicarbonate works well. But this consumes reagents and loses 2b4mp itself.
I don't see the point in flushing 2b4mp, it's better to flush the meph oil after synthesis. The procedure is the same, but it's more convenient.
 
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It is especially nice to dry a wet 2b4mp after washing.:) After all, you can't put it in the bag wet and not know the exact weight. And it takes a very long time to dry and exudes tear fumes.:cry::sick::poop:
I summarize this topic as follows. If you are brominating, it makes sense at this point to wash 2b4mp while it is liquid.
If you bought a finished 2b4mp and want to wash it and store it, you shouldn't do that. The best way to wash 2b4mp is to wash it in solvent.
Consider it!
 

thevines2

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Been trying to find ways to clean up 2-Bromo-3,4-methylenedioxypropiophenone without much luck
 
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