4-mmc turn red. Why?

[w2x3f5]

It’s worth measuring the melting point of your 2b4m sample, it should be about 74-77 degrees approximately. I suspect that there are impurities in your 2b4m

 

[HeavenChem]

Problem also can be in DCM if his supplier added alcohol in there. I had almost same issue. This color can't be washed with acetone or ethyl acetate. Only isopropyl alcohol helps, but with high loses

 

[w2x3f5]

Dichloromethane usually contains ethanol, it is needed to stabilize dichloromethane. 0.5 percent ethanol is unlikely to affect the reaction so much, but dirty 2b4m easily affects. Perhaps there is no ethanol impurity in dichloromethane for analysis.

 

[HeavenChem]

Stabled DCM won't affect, but if supplier added much more, it can cause major problems which I had.

 

[DavidNichols]

Ethanol wont cause and problems. Its methylaniline byproduct from dirty precursor.

 

[HeavenChem]

IPA with acetone can give red colors

 

[chudakrekt]

When acidifying, the temperature should not exceed 30*C, if up - place in water
Use mixer speed 180-250
Use isopropyl alcohol to add acid After you have reached Ph 5-5.5, you can evaporate a quarter of the liquid and put it in the freezer, thereby skipping the step of obtaining flour and immediately getting crystals
I have created more than 600 kg of this substance, I think I will write manuals for this forum in which I will tell about all the possible mistakes of beginners, show all the tricks and possible synthesis options

 

[HeavenChem]

Lol, metal mixer on acidification process ? Sounds like grey color failure on finish

 

[TheVacuumGuy]

Please enlighten me. Why would one add more acid when ph target reached?

 

[HeavenChem]

Did you knew what 2-3pH resulting degradation of 4-MMC ?

 

[TheVacuumGuy]

Still waiting

 

[HeavenChem]

Problem can be in local over-acidification.
When you adding acid too fast your 4-MMC turns in to shit.
Place your beaker on ice bath with magnet stirrer and under separation funnel. Reaction temperature should be not more than 25-30 degrees Celsius. Use about 2-3 drops of concentrated hydrochloric acid per second on 1000g of bromoketone-4
Also red color can be from alcohol in reaction mass. Make sure what your DCM is pure.

 

[chudakrekt]

About the speed of adding is true, but there are methods with very fast moving You can also use hydrochloric acid IPA

 

[HeavenChem]

In that case you should not use acetone. I don't like IPA methods anyway