Tkuze
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Problems with NaCNBH3, weird insoluble inorganic salts
I recently started a new project with a new investor and ordered a new bottle of NaCNBH3 for reductive amination. I carried out a reaction using well
known conditions and obtain a lot of inorganic solids that dont dissolve in any solvent, concentrated acid or base and the main product was obtained
in a very small yield with what seems to be mostly polymerized minor products. This reaction worked on a small scale before using my previous NaCNBH3.
My new bottle is from Beantown Chemical >95% and is not expired and brand new from them. I requested to COA and have yet to hear back. Does anyone
know what these inorganic solids may be ( other than the boric acid and NaCN resulting after quenching, which is removed during workup) or what may be
wrong? The only variable change is this chemical batch and reaction temp might be 2-3C higher due to ambient temp change. This was taken into
consideration though, as experiemnts were run in triplicate in a water bath to keep reaction temperature correct. It seems 1 h into the reacrion,
precipitant forms and after workup, it ia stuck to all the glass vessels. I dont have an analytical device to charqcterize this and have no idea whats
happening. Thanks for any imput
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Sulaiman
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This level of chemistry is way above my experience but;
1) re-read original and current notes
2) order enough Sodium Cyanoborohydride from a different trusted source to test your procedure(s) asap
Without suitable analytical materials and equipment you could possibly keep guessing until Christmas 
CAUTION : Hobby Chemist, not Professional or even Amateur
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Tkuze
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You said it best. Did #1 exhaustively
2) in my opinion, the best way to solve this and you are spot on. I am just waitint to get the certificate of analysis from the company. And think I
will just have to do that. Thanks for your advice. Btw, I tested my compound using GAA under N2 at a miligram scale and H2 evolution was apparent. So
it works. And ive use this reagent for so many different types of reacrions and characterize via NMR and they work and ive never had this problem. It
has to be a bad lot of NaBH3CN. Its just shitty because I switched companies to get larger quantities at supposed higher quality and a much better
price. I looked through the 10 papers used in a variety of different reacrions that have all worked multiple times with no complications and the
materials section and they use the same grade(albeit different chemical supplier) ~>95% reagent. In graduate school I used Beantown to buy very
specialized compoinds for use in mouse studies, therefore needed the upmost quality( PEG-X00 compounds with various terminal structures, sensitive
biological linking compounds) starting materials to make our FDA approved compounds for drug delivery formulations and to conduct binding constant
studies and had no problem. I have a to do list to figure out this problem and a million ideas of what could have gone wrong... but repeated the test
reaction in triplicate with extreme precision and it is jjsy so wrong. Like I can ususally eyeball the crude product or smell it and see if its good(
since its like our lab's main hit compound and I ship it to tons of university medical departments) before I run a crude NMR, run a column, then know
the fracrion with my compound and get a consistent yield. My triplicate results using the simplest model were a fucking quagmire.
Ultimatelty, overcomplication is killing me. The only thing is I have a private company with a private investor and budgets arw strict. I have to find
out this stuff is bunk and get a refund or new batch, or revert to a diffwrent supplier which is less professional and doesnt have as much quality
control ( they are mainly a biological supply conpany). I think instead of just wasting my time purifying and analyzing every single compound in the
products, i just need to toss them and begin fresh, because given a confirmed pure and proper reagent, this problem wont occur. Wish I could answer
the quesrions ive been obsessing over, but I have deadlines.
I do know dimethyl sulfide and borate esters are impuriries left from industrial production, but on a sub mmol scale, it should not be present in
large amounts. After workup and require all glassware used to be washed and scrubbd with concentrated acods and bases. Quenching with Na2C03 dropwise
under N2, reducing solvent in vacuo and adding 20mL water and DCM should and indeed did previouslt leave a clean partition with no precipitant.
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Sulaiman
International Hazard
Posts: 3721
Registered: 8-2-2015
Location: 3rd rock from the sun
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When I started as a repair engineer one of my biggest problems was spending more time determining how and why things worked and failed,
than just quickly repairing it and earning more cash for my employer.
I have not changed much 
Over time this made me more efficient, but employers don't invest in people - so I just carry on my way.
As you are an investor, you do not have time to learn, just earn, earn, earn 
CAUTION : Hobby Chemist, not Professional or even Amateur
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Tkuze
Hazard to Others
Posts: 108
Registered: 8-5-2019
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I decided to dive into the literature and then found the answer from a very skilled member of this site. I had to learn in this case! But yes, gotta
spend some extra money to move forward when needed, but explore when you need to make a standardized procedure or find out that something you thought
was a problem was really just an interestimg aside that can be utilized.
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