MgSO4 Bind To Amines (Kill Yield ?!)

[Mr Gargamel]

Hello while purifying 1n and 2n amines i get 0% yield while bubbling hcl in toluene+amine product (50g amine in 300ml toluene) -(i used 20-30 MgSO4 to pre-dry organic phase)

i google little bit and i found that MgSO4 is incompatible with acid sensitive compounds

please check out :

4.7: Reaction Work-Ups

A key step in conducting a reaction and isolate the product comes immediately after the reaction is complete, and is called the reaction "work-up" . The work-up refers to methods aimed at …

chem.libretexts.org

can it be possible that the MgSO4 absorb all my product and ruin my yield ???
and if soo how is it possible that this MgSO4 absorbent i used soo commonly in tutorial to product and gas out mdma + meth ?

 

[Osmosis Vanderwaal]

You say, " I used 20-30 MgSo4...", 20-30 Grams?! To how much solvent? 300 ml? 30g sulfate can absorb 15g water, which is 5% of your organic solvent..

 

[Mr Gargamel]

yes is used almost 20g of this stuff for 400ml toluene solvent....
i see that many of the tutorial use this much.... (20-50g per +-0.5L solvent)
why peoples use the MgSO4 if it attract amine?
NaOH Should be more suitable for dry amines ..... no ?
or i miss here something ?

 

[Mo0odi]

Cool

 

[Osmosis Vanderwaal]

Sodium hydroxide to dry something? I'm not a chemist, but I use it to neutralize acid, clean my drains ect. Once I did an A/B extraction and used vegetable oil as my non-polar. I neutralized it with lye and guess what happened.... It turned into soap 🫧. It might be a good desiccant, but I wouldn't use it as a drying agent. It dissociates in water to Na+ and Oh-, so no it couldn't be a drying agent

 

[Mr Gargamel]

i see that for example they use KOH to dry aniline (which is primary amine btw) for a reason i guess... (look at nile red tutorial on youtube)
i find in 2-3 sources that MgSO4 is acidic and is not recommended for amine.

btw i just successfully dry the toluene with NaOH, i use it as desiccant because currently i don't have any KOH which is stronger dessicant.

Despite all of my research i don't understand why in most of the tutorial they are using the MgSO4 desiccant.
they are lake of knowledge or i miss here something ?

 

[Osmosis Vanderwaal]

I'm going to stop commenting and make room for someone who knows more than I, but that list is missing the best drying agent there is,

Spoiler: don't peek :)

Molecular sieve

it's inert, reusable, can be left in the solvent works at below freezing and doesn't absorb anything larger than water (3ã)

 

[Ortist]

unlikely that 20gr of MgSO4 caused such a disaster.

is your roluene mix still basic or neutral?

Ethylacetate works perfectly for gassing.

 

[Mr Gargamel]

yes ... i purify dimethylamylamine first run no MgSO4 i get nice crop of white snow flakes suddenly after gas (dry by fractional distillation).
second run i used MgSO4 once i added the wet freebase to the toluene+MgSO4 solution it was cloudy, after i filter it off and gas it get nothing.
(Only light pink Acidic solution looks like SLP)

in another small test run i use NaOH to dry i get snow flakes ... once i gas it to very acidic level the flakes re-dissolve to give clear toluene solution, i try to blow it with alot of air while stirring and the flakes come back, it looks like the acidic solution of HCL-Toluene able to dissolve the Product. anyone know about this ? ?
anyway i was able to recover the crystal by just blowing the HCL out of the toluene with air from my mouth.

 

[Raz]

I've had the same issues when drying my post reaction solution with MgSO4. Crap results. My guess is that MgSO4 doesn't actually do anything to the amines, but since the amines would be more attracted to any water in the solution they would become trapped in the swelling MgSO4 as it clumps together absorbing any water.
Most of what you read online posted by people and find online is purely theoretical or repeated information that people read. Hardly none of it is from hands on experience I've noticed. So a person has to take any information they read and double check it to see if it makes enough sense to be true. Such as using MgSO4 to dry solutions post reflux. Sure MgSO4 will work fine for large batches, only cause it can't catch all the amines since there's only a small bit of water that would be packed full of amines. Most likely the reason for constant low yields being reported in all the older write ups. So in small test run reductions once the MgSO4 is added to dry the solution almost all of the product is in the small amount of water and then ends up trapped in the swelling MgSO4.