Bromação de 4′-Metilpropiofenona para 2-bromo-4'-metilpropiofenona. Grande escala.

[QAZ123123]

The proportion in the video：

4-Methylpropiophenone (250g)
Hydrobromic acid 48% (191ml/285g)
Hydrogen peroxide 37% (103ml/116g)

The ratio here：

• 4′-Methylpropiophenone (cas 5337-93-9) 1000 g;
• Hydrobromic acid 48% aq. 1140 g or 765 ml;
• Hydrogen peroxide (H2O2) 35% 328 g or 290 ml;

The dosage of hydrogen peroxide varies，How much hydrogen peroxide should I add?

 

[William Dampier]

Based on experience, it’s best to use an excess of hydrobromic acid (approximately 1:1 by volume to the ketone). You add peroxide until the in situ generated bromine reacts. The exact amount may vary depending on the temperature conditions and degradation rate. This is better than creating ideal conditions, as you can control the reaction visually.

 

[Pier]

That's not what I asked.

can be used Erlenmeyer Flask 5000 ml for this synthesize​

 

[William Dampier]

It’s better to use a round-bottom flask or a flat-bottom flask to minimize the evaporation of bromine vapor from the reaction mixture. An Erlenmeyer flask is for other tasks, but if you don’t have another flask, you can use that.

 

[s7xm]

I would like to ask,After 12 h precipitate is formed.Sodium bicarbonate aq solution is added to the reaction mixture to reach neutral pH 6-7, stir it well.What concentration of sodium bicarbonate solution should I use?
Or add water first and then slowly add sodium bicarbonate to make the pH value of the flushing water solution reach 6-7

 

[s7xm]

To clean acidic crystals, a 1% to 2% sodium bicarbonate aqueous solution can usually be used. The concentration of sodium bicarbonate can also be adjusted according to the specific situation of the acidic crystals. For example, highly acidic crystals may require a more concentrated sodium bicarbonate solution.
Specifically:
Generally acidic crystals: 1% to 2% sodium bicarbonate aqueous solution is a more commonly used concentration, which can effectively neutralize the acidity and avoid damaging the crystals.
Highly acidic crystals: The concentration of sodium bicarbonate can be appropriately increased, such as 3% or 4% solution.
Special cases: If the crystals are also sensitive to weak alkaline solutions, consider using a lower sodium bicarbonate concentration, or use other weak alkaline solutions.
Other precautions:
Solubility:
Sodium bicarbonate has limited solubility in water. Generally speaking, a concentration of 1% to 2% is already relatively easy to dissolve.
Operation:
When cleaning, you can first immerse the crystals in a sodium bicarbonate aqueous solution, and then gently wipe them with a soft brush or cotton cloth.
Rinse:
After washing, you need to rinse with pure water to remove the residual sodium bicarbonate solution.
In general, it is a common and safe practice to use 1% to 2% sodium bicarbonate aqueous solution to clean acid crystals. If you encounter special circumstances, you need to adjust the concentration according to the specific situation.

Can I follow this method?

 

[xoxo2.0]

fuckk man just made some 2b4m today and this shit is hell of a irritant (My carelessness for trying to air drying before reading the safety sheet) but dude my lab now reeks of this and after 9 hours there is still mild irritation to eyes and skin when entering into lab.

And for some reason yields are moderate not as high as texts say, although this was my first time doing this so i did mess up somewhere for now its probably the addition of H2O2 i think i stopped bit too early believing that most of the ketone is brominated and further bromine is not being consumed.

 

[William Dampier]

u need to treat the room with a dilute solution of sulfuric acid, and you should do this several times, also using household cleaning agents. I understand what you’re talking about, and these lachrymatory properties will persist until you break down the particles remaining in your room. It can evaporate for a very long time if these substances are not forcibly degraded.

 

[xoxo2.0]

Thanks I did proper cleanup with household cleaning agents and it still took a week toh completely get back to normal next time I'll be much more careful

 

[TayRonz]

Hey,
In case I won't manage to find HBr 48% - will the following method work?
4'-methylpropiophenone in the flask together with NaBr or KBr salt and diluted H2SO4(aq), then add dropwise 35% H2O2 in order to create Br2 in situ which will react with 4'-mp, creating the desired 2b4m.

I will obviously adjust the quantities of the salt/acid/H2O2 in order to achieve equivalent moles of Br2 compared to your guide (maybe with a slight excess even).

What do you think of this method?

 

[William Dampier]

If you are considering such routes, I would suggest using bromination in ethyl acetate with copper bromide under heating.