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Bromination of 4-methylpropiophenone with HBr/H2O2 (large scale)

William Dampier

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Reaction sheme:
QmU05KGcDH


Reagents:
4-methylpropiophenione 1000 g,
Hydrobromic acid 48% aq. soln. 1300 g,
Hydrogen peroxide 35% 750 g,
Baking soda,
Water.

Preamble:
The bromination reaction is easily scaled under these conditions. Basic rule - add peroxide slowly to avoid splashing the reaction mixture. In the role of a mixing device, it is better to use the overhead stirrer, the magnetic stirrer does not cope with the sediment. The blades of the mixers must be covered with teflon to avoid reactions with HBr acid.

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Synthesis:
1. 1000 g 4-methylpropiophenone added to the flask.
2. 1300 g 48% HBr acid poured in flask and stir 5 minutes.
3. 750 g 35% hydrogen peroxide added to the drip funnel.
4. Dropwise hydrogen peroxide to the stirred reaction mixture.
5. In the process of adding peroxide in the mixture, a bromine is released, and with stirring dissolves reacting.
6. It is necessary to add at a rate such that the bromine discolored.
7. Control the temperature of the reaction (>75 *C), we do not give boiled mixtures.
8. The second half of the reaction discoloration can go longer, add peroxide, focusing on temperature growth.
9. How all the peroxides added, leave the reaction to night on stirring at room temperature.
10. The next day, we see precipitation.
11. Add a saturated soda aqueous solution, drain the water from the sediment from the flask through the sieve, rinse with re-clean water.
12. Use the crude bromoketone for further reactions with theoretical calculation of the yield until 1500 g.
 
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dk77

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Reaction sheme:
View attachment 1290

Reagents:
4-methylpropiophenione 1000 g,
Hydrobromic acid 48% aq. soln. 1300 g,
Hydrogen peroxide 35% 750 g,
Baking soda,
Water.

Preamble:
The bromination reaction is easily scaled under these conditions. Basic rule - add peroxide slowly to avoid splashing the reaction mixture. In the role of a mixing device, it is better to use the overhead stirrer, the magnetic stirrer does not cope with the sediment. The blades of the mixers must be covered with teflon to avoid reactions with HBr acid.

Synthesis:
1. 1000 g 4-methylpropiophenone added to the flask.
2. 1300 g 48% HBr acid poured in flask and stir 5 minutes.
3. 750 g 35% hydrogen peroxide added to the drip funnel.
4. Dropwise hydrogen peroxide to the stirred reaction mixture.
5. In the process of adding peroxide in the mixture, a bromine is released, and with stirring dissolves reacting.
6. It is necessary to add at a rate such that the bromine discolored.
7. Control the temperature of the reaction (>75 *C), we do not give boiled mixtures.
8. The second half of the reaction discoloration can go longer, add peroxide, focusing on temperature growth.
9. How all the peroxides added, leave the reaction to night on stirring at room temperature.
10. The next day, we see precipitation.
11. Add a saturated soda aqueous solution, drain the water from the sediment from the flask through the sieve, rinse with re-clean water.
12. Use the crude bromoketone for further reactions with theoretical calculation of the yield until 1500 g.
Another hydrobromic acid synthesized by Hans-Dietrich is 780ML, here 1300 hydrobromic acid. What is the difference between oxidizing liquid 136ML and 750ML?
 

William Dampier

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1300 g (or 1L) aq. HBr 48% - 1,2eq for 4-methylpropiophenone
 
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dk77

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Sorry, when the hydrogen oxide reaches 500 grams it turns red instead of changing color, then a deeper red when added. Need to finish adding?
 
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William Dampier

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Sorry, when the hydrogen oxide reaches 500 grams it turns red instead of changing color, then a deeper red when added. Need to finish adding?
Continue stirring until discoloration. If no discoloration occurs, stop the reaction. The proportions given are those with an excess of hydrobromic acid and peroxide, but they may be reduced (1,1KG HBr48% and 0,65KG H2O2)
 

dk77

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Continue stirring until discoloration. If no discoloration occurs, stop the reaction. The proportions given are those with an excess of hydrobromic acid and peroxide, but they may be reduced (1,1KG HBr48% and 0,65KG H2O2)
Since English is not my native language, I may not express well. I mean, when it starts dripping, it changes color and then becomes transparent, but after the critical point it becomes opaque and the whole thing turns red. Is it time to stop? Is it bad to add too much hydrogen peroxide? I stop when he turns red and can't change color because I don't know when to stop, then once the temperature drops, crystals form. I don't know if this is 2-bromo-4-methylpropiophenone. I will add pictures later. thank you for your help.
 
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William Dampier

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Since English is not my native language, I may not express well. I mean, when it starts dripping, it changes color and then becomes transparent, but after the critical point it becomes opaque and the whole thing turns red. Is it time to stop?
Not always, maybe you need more time, oriented on the proportion above
Is it bad to add too much hydrogen peroxide?
No problems, anything, excess will not hurt
I stop when he turns red and can't change color because I don't know when to stop, then once the temperature drops, crystals form. I don't know if this is 2-bromo-4-methylpropiophenone.
These crystals - 2-bromo-4-methylpropiophenone
 

hlebsladky2

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Apr 10, 2022
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Reaction sheme:
View attachment 1290

Reagents:
4-methylpropiophenione 1000 g,
Hydrobromic acid 48% aq. soln. 1300 g,
Hydrogen peroxide 35% 750 g,
Baking soda,
Water.

Preamble:
The bromination reaction is easily scaled under these conditions. Basic rule - add peroxide slowly to avoid splashing the reaction mixture. In the role of a mixing device, it is better to use the overhead stirrer, the magnetic stirrer does not cope with the sediment. The blades of the mixers must be covered with teflon to avoid reactions with HBr acid.

Synthesis:
1. 1000 g 4-methylpropiophenone added to the flask.
2. 1300 g 48% HBr acid poured in flask and stir 5 minutes.
3. 750 g 35% hydrogen peroxide added to the drip funnel.
4. Dropwise hydrogen peroxide to the stirred reaction mixture.
5. In the process of adding peroxide in the mixture, a bromine is released, and with stirring dissolves reacting.
6. It is necessary to add at a rate such that the bromine discolored.
7. Control the temperature of the reaction (>75 *C), we do not give boiled mixtures.
8. The second half of the reaction discoloration can go longer, add peroxide, focusing on temperature growth.
9. How all the peroxides added, leave the reaction to night on stirring at room temperature.
10. The next day, we see precipitation.
11. Add a saturated soda aqueous solution, drain the water from the sediment from the flask through the sieve, rinse with re-clean water.
12. Use the crude bromoketone for further reactions with theoretical calculation of the yield until 1500 g.
What does a crude bk4 look like? Btw, to do methylamination should I wait to the whole substance to become crystal or I can skip waiting for a night?
 

William Dampier

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What does a crude bk4 look like? Btw, to do methylamination should I wait to the whole substance to become crystal or I can skip waiting for a night?
Wait for the crystallization of the substance. Raw and washed looks the same as dry, only wet
 

hlebsladky2

New member
Joined
Apr 10, 2022
Messages
7
Reaction score
1
Points
3
Reaction sheme:
View attachment 1290

Reagents:
4-methylpropiophenione 1000 g,
Hydrobromic acid 48% aq. soln. 1300 g,
Hydrogen peroxide 35% 750 g,
Baking soda,
Water.

Preamble:
The bromination reaction is easily scaled under these conditions. Basic rule - add peroxide slowly to avoid splashing the reaction mixture. In the role of a mixing device, it is better to use the overhead stirrer, the magnetic stirrer does not cope with the sediment. The blades of the mixers must be covered with teflon to avoid reactions with HBr acid.

Synthesis:
1. 1000 g 4-methylpropiophenone added to the flask.
2. 1300 g 48% HBr acid poured in flask and stir 5 minutes.
3. 750 g 35% hydrogen peroxide added to the drip funnel.
4. Dropwise hydrogen peroxide to the stirred reaction mixture.
5. In the process of adding peroxide in the mixture, a bromine is released, and with stirring dissolves reacting.
6. It is necessary to add at a rate such that the bromine discolored.
7. Control the temperature of the reaction (>75 *C), we do not give boiled mixtures.
8. The second half of the reaction discoloration can go longer, add peroxide, focusing on temperature growth.
9. How all the peroxides added, leave the reaction to night on stirring at room temperature.
10. The next day, we see precipitation.
11. Add a saturated soda aqueous solution, drain the water from the sediment from the flask through the sieve, rinse with re-clean water.
12. Use the crude bromoketone for further reactions with theoretical calculation of the yield until 1500 g.
Hey! How much should I add of a saturated soda aqueous solution? Thanks.
 

William Dampier

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Hey! How much should I add of a saturated soda aqueous solution? Thanks.
We look when the reaction has ceased to discolor. After this and crystallization of the product, we can add dry soda. Add while stirring in small portions until the red color disappears and the reaction stops bubbling.
 

hlebsladky2

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We look when the reaction has ceased to discolor. After this and crystallization of the product, we can add dry soda. Add while stirring in small portions until the red color disappears and the reaction stops bubbling.
Thanks! As for the distilled water to add, should it be equal to the reagent volume?
 

William Dampier

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Thanks! As for the distilled water to add, should it be equal to the reagent volume?
It does not matter, you can add water to the entire volume of the flask, but at least one equivalent of the volume of the reaction mixture
 

ZhengJi

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Which solvent is best for recrystallization 2-bromo-4'-methylpropiophenone? I have tried this method but my 2b4mpp is a little bit dirty - white instead of colorless cristal.
 

dk77

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Which solvent is best for recrystallization 2-bromo-4'-methylpropiophenone? I have tried this method but my 2b4mpp is a little bit dirty - white instead of colorless cristal.
Post a photo and I'll see if it's the right product
 

dk77

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Which solvent is best for recrystallization 2-bromo-4'-methylpropiophenone? I have tried this method but my 2b4mpp is a little bit dirty - white instead of colorless cristal.
Have you ever bought or produced a transparent and colorless product?
 

William Dampier

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Joined
Jul 19, 2021
Messages
580
Reaction score
347
Points
63
Which solvent is best for recrystallization 2-bromo-4'-methylpropiophenone? I have tried this method but my 2b4mpp is a little bit dirty - white instead of colorless cristal.
White color is good for this, it should not be transparent (although large crystals grow under some conditions)
 
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