First time backsalting

[m4estr0]

Hello,

I'm backsalting 100 mL toluene with 0.0531 mol/L HCl (this concentration is such that 100 mL will salt exactly 1 g of DMT), added in 25 mL steps and pH measured after each step (titration). The intension is to precip freebase directly out of water with ammonia in the next step.

After 200 mL was added, pH dropped to 4-5.
It's my first time ever doing titration. Started with 100g MHRB (powdered), so I guess >1% yield.

Now my question: My toluene + water mixture has a toluene phase (on top), and a "soapy" water phase:

Is this something to worry about?

Btw, the water phase looks yellow on this photo but it is colorless in real life.

It seems that the more acid was added, the soapier the whole thing became. When shaking the mixture, there are many small bubbles in the water phase. Letting the mixture sit, the bubbles become larger over time, until they look no longer like bubbles but more like long threads, "spiderwebs" in the water phase.

Another thing that I may have done "wrong" is only using 0.57g of NaOH per 1g of MHRB. Also, why is it that when pulling NP from basic soup, plenty of NaOH is reported to break emulsions, even though it causes saponification?

 

[doubledog]

That pH changes are weird, but otherwise it went normal, the ammonia wash at the end is really good idea.
I would advise against A/B, it's much more work due to boiling and reducing and yields are not higher.
Funny part of the process is mainly in nps and backsaltings phases.

 

[m4estr0]

It seems the DMT was still wet when it was weighed. All the DMT combined was weighed again and only 800 mg, so 0.8% yield. Perhaps a 3rd toluene pull should have been done on the basic soup (which I still have). Or more likely the volume of ammonia washes was way too big and a lot of DMT dissolved in them. With the final wash it seemed like the DMT was dissappearing before my eyes! (or maybe it was sodium carbonate like downwardsfromzero suggested)

There are still things I don't understand. At pH 11 (first mini A/B re-base), 99.5% of DMT should be in freebase form. Then why did pH 14 (second mini A/B re-base) crash out so much more DMT (volume of water was the same: 400 mL) ?


A/B seems to have its proponents on this forum. My hope with A/B is a less muddy basic soup and quicker emulsion separation after shaking. Also, smaller volumes (basic soup fit barely in 1 liter erlenmeyer, largest one I got that has a PTFE stopper) and much less NaOH needed. According to one user, the acid soaks can be done rapidly by siphoning rather than filtration, and reducing can be done directly on a stove on high heat without reported losses.