Questions about Bariums aq. NaBH4 reduction

mimic · Fri Sep 30, 2005 8:35 am

Know anything about this route?
https://www.synthetikal.com/Rhodiums_pdfs/chemistry/redamin.aqueous.nabh4.html

Isnt NaBH4 used up in this reaction?
Why would anyone dream of using less then 1:1 molar ratio?
Would a dream be more pleasant pushing it towards completion with 1.1:1?
Would that just be opening the door to other unwanted products and reactions?

How much of a molar excess of amine is a bad thing?
Is this just a cost and availability issue?

How does this sound...
math idiot--->28.9g mdp2p(65mmol)
178.02 x .065 = 11.5713
edit--->11.6g mdp2p(65mmol) was dissolved in 50ml toluene and to this was added 10.1g 40% aq. Methylamine(130mmol) and mag stirred on high for 2hrs. The aqueous phase was then removed and the toluene phase was transferred to a 250ml rb flask containing 2.5g NaBH4 (65mmol), 25ml water and 15ml EtOH and the mixture was vigorously stirred for a further 3 hours at room temp. A/b wash and gas for goodness.

WTF is room temperature? (Drop wise addition like snipe pooping...)
Rooms in Syria are a lot different then in Siberia.
What is the optimum temp for NaBH4 reductions like this? LabTops old stuff is all very cold, but I beleive that some of that is a methylamine gas solubility issue.

Can the non polar usual suspects be substituted for the toluene as acquisition dictates?
DCM, Xilene?

Could a ptc and distillation for clean up bee used?
409 or BAC piercing/tattoo solution?
Could the alcohol and water in the addition of NaBH4 then be omitted?

With ptc one could really cut down on the solvent use and recycle most of the rest with careful fractional distillation, I think.

Thank you Barium!

tom-a-rom-rinbow · Fri Sep 30, 2005 11:40 am

room temperature is 20 C = 68 F.

anime · Fri Sep 30, 2005 1:35 pm

People 'dream' about using less because in reality you don't need a 1:1 ratio to reduce the imine to an amine but since water is involved it changes things.

Adding more NaBH4 will definitely help yields.

No, generally there will be no additional impurites due to the addition of excess NaBH4. (although you are currently using an excess)

Methylamine is very soluable in MeOH or H2O, so evaporation isn't a big issue here.
Xylene will work in place of toluene in the reaction. (But they're both cheap). PTC is difficult to seperate from the amine unless your distill.

Radiumhero · Sat Oct 01, 2005 1:17 pm

Well yust like anime said the only way to get complete conversation to amin
will take an exess of about 1:4 substrat : NaBH4... depending on tmp and
quality of the substart

mimic · Sat Oct 01, 2005 11:54 pm

Bariums #s
11.6g mdp2p(65mmol)
10.1g 40% aq. Methylamine(130mmol)
2.5g NaBH4 (65mmol) <---reaction example was 1/2 this

LabTops #s
https://www.synthetikal.com/Rhodiums_pdfs/chemistry/redamin.nabh4.html
11.6g mdp2p(65mmol)
3.47g Methylamine gas (112mmol)
1.16g NaBH4(31mmol)

LabTops #s are in line with the original Barium numbers (1mol tone:.5mol amine), but barriums had a comparativly terrible yield, but with a much quicker reaction time. Barriums ran at 20c while LabTops addition at 5-15c and allowed to warm to room temp and run for 2days(ending temp 25c).

More questions...
Is LabTops need for a 5-15c addition just a complication of the scale of his reation?
Would Barriums also require cooling if scaled up?
How hot is too hot for the addition?
Would it be a good idea to greatly extend the reation time for Bariums reaction?
How exactly is NaBH4 working in this reation?
Im guessing that each of those 4 hydrogens are going to work meaning that 1mol amine:.5mol NaBH4 is really a 2x molar excess of NaBH4 and 1:1 a 4x excess.

I am very ignorant, so please slap me with the trout of truth if im incorrect.