Al/Hg Nitro Synth regarding flask size ???

Pemulwuy · Sat Apr 16, 2005 10:25 am

300 micron thick AL
100 Ketone
100 Nitro
3 Litre flask
Overhead Stirring

1 day

80 - 90% w/w ketone to salt everytime.

bio · Working Bee

[quote="Pemulwuy"]
300 micron thick AL
100 Ketone

Pretty damn nice. How many grams Al and what is the ketone?

Rather than reverse engineer this maybe you might post a few little details.

icecool · Insistent Chemist

Isn't 300micron Al a bit small to do a reductive amination with a Hg salt?

IndoleAmine · Dreamreader Deluxe

This yield is nothing special (unless he used abnormally small amounts of Al of course Very Happy

).

Using the standard MethylMan nitro Al/Hg writeup, a 100% w/w yield ketone/amine salt can be easily accomplished...
(not to talk about making the imine beforehand, with preformed MeAm and with the aid of mol.sieves to dehydrate... Very Happy

)

I think 300micron (0.03mm) foil thickness were meant, of course NOT 300micron particle size! (DANGEROUS!)

i_a

sony · Wed Apr 27, 2005 7:09 pm

What is the reason that H2O is used in these Al/Hg reactions ? Is this perhaps for H2 generation?

icecool · Insistent Chemist

It is so the Cl- and the Hg2+ can dissolve...

sony · Wed Apr 27, 2005 9:30 pm

Mercuric chloride is also soluble in acetic acid and alcohol so that would be a rather weird reason.

bio · Working Bee

Water is not necessary in this reaction although a little doesn't seem to hurt. Even when using dry solvent water is present and water is produced 1:1 molar ratio due to insitu imine formation.

There is a lot of conflicting information on this subject as the Hydrogen is not the actual reducing agent, rather the reaction of the imine with the Al complex at the surface of the aluminum itself.

Some claim a little water added when using dry methanol (which is not anhydrous) improves the yield and causes a hotter reaction. The RA MeOH used around here is .02% water. Experiments were done using up to 20ml H2O per mole ketone and no noticible difference was observed in yield or reaction rate. This using RA MeNO2 and unsubstituted ketone.

A very little water added to the MeOH does speed the HgCl2 dissolution as does warming especially if using more HgCl2 as Joe the clever neighbor does.

One thing definetly known is when using the Shulgin
method w/ P2P yields were not very good, due I believe to the presence of excess water. IndoleAmine can probably elaborate further on this.

sony · Thu Apr 28, 2005 3:22 pm

Thanks for the information indeed i did not expect the hydrogen to be the reducing agent, too bad there isnt much info to be found on the definitive mechanism either nor for the al/hg reduction of nitroalkenes.

IndoleAmine · Dreamreader Deluxe

Water IS necessary, since the Hg salt has to dissociate into Hg(2+), OH(-) and HCl to be able to amalgamate the foil properly.
OTOH, water prevents imine formation between ketone and MeAm - so its best to use a catalytic amount only.
This tiny amnt. is present in most solvents anyway...

HgCl2 dissociates as soon as it dissolves in a suitable solvent (H2O, EtOH, GAA, DMF etc.) - no matter which solvent is used, as long as it no nonpolar!
Nonpolar solvents don't dissolve inorganic salts because the dissociated ions wouldn't be soluble it it - as long as the solvent is at least slightly "polarizable", ionic salts will dissolve in it at a certain rate.. Exclamation

tom-a-rom-rinbow · Sat May 07, 2005 2:25 pm

Abacus has already figured how to process 1 mol of ketone per 2L flask per day using MeNO2-

http://12.162.180.114:90/synthetika/hiveboard/methods/000382493.html

he uses Al flashing to make the nitro reduction controllable on a larger scale. then it is easy to separate the MeNH2 as 5-6% solution by basifying and distilling from the amalgam sludge. this is used in Osmium's MeNH2/Al/Hg procedure, which is easier to control, stir, and scale as it requires only 1/4 as much Al per mol.

swim scared himself with a runaway MeNO2 reduction with thick Al foil in a 500 mL once, and later switched to hexamine + HCl processed as in the OrgSyn procedure using NH4Cl + formalin. He was happy with that procedure, though the purification process is long and filtering heaping quantities of MeNH2.HCl on too small a funnel can take quite a long time...

as for the 500 mL flask someone mentioned- swim used one several times to comfortably reduce 20g of ketone using Oz's procedure with R regular aluminum foil (except swim adds MeNH2.HCl solution to the amalgam, then NaOH soln) yielding 18-20g hcl salt typically. a strong reflux starting after ~1/4-1/3 the ketone is added is a good indicator of a successful reaction.

swim sometimes distilled ~3% MeNH2 in MeOH from post-rxn mixtures after extraction...

in the amalgam workup, you do not actually need as much NaOH as MethyMan says. he keeps adding conc NaOH until separation, when what is needed is enough H2O to make the MeOH/H2O mixture more dense than the toluene or xylene he is extracting with! swim does not see the point of basifying past pH 13 (approx 10% the NaOH MethylMan uses) and has gotten 86 % m/m yield hcl salt without doing so.

bio · Working Bee

I swore I'd never do it again but just deleted the reply written. Sad

Would any of the computer weenies out there maybe know a way to retrieve a self deleted reply if the page was not changed?

Anyway here's part of it and Abacus if you are out there send me a mail as there is something you would be interested in regarding a mutual endeavor.

The Abacus procedure is very good. A 3% solution is about what is distilled. Use ice cold condensing and receiver in ice/water, keeping condensation out. Filtering off the Al then adding more works well w/o distilling. Titrate at least the first time.

Succinct enough Syn? Damn, hate it when I do that.

bio · Working Bee

I swore I'd never do it again but just deleted the reply written. Sad

Would any of the computer weenies out there maybe know a way to retrieve a self deleted reply if the page was not changed?

Anyway here's part of it and Abacus if you are out there send me a mail as there is something you would be interested in regarding a mutual endeavor.

The Abacus procedure is very good. A 3% solution is about what is distilled. Use ice cold condensing and receiver in ice/water, keeping condensation out. Filtering off the Al then adding more works well w/o distilling. Titrate at least the first time.

Succinct enough Syn? Damn, hate it when I do that.

QuickFitAbuser · Quality Control

My 2 cents worth.

When doing Rxn's, allow for 40 -50% 0f the Rxn vessel/flask to be filled, MAX.
Another source of good, pure Al is TIG welding rods. Guarnteed 99.99% pure, and from my experience , the thicker the foil/rod, the better. Nil silicon and are available in Diameters from .75mm to <3.5mm. I prefer the 1.00 mm ones with Hg, as the dissolve slowly and controllably.
Reaction is best performed in a small, concentrated space with just enough room (including condenser) to create the desired catalyst ( solid liquid gas).
If your condensor is working about 1/3 the way up, after a slow increase in temp ( patience) it should be good.
I would not do a 1 ltr Rxn in a 5 ltr flask , to much dead space and low yield.
Either scale up your equipment, or down your precursurs.

Foil is ok, but as I say, the thicker the Al the better, also easy to cut and ball up.
No change.

icecool · Insistent Chemist

What would be bad about thin foil.
SWIM uses his Al foil 1 layer thick it isn't extra heavy or thick.
And put's it just as a big piece in the mixer and makes these crumbles.
And when adding the Hg salt in 3-4 portions it works veeeeeeery smooth.
He is doing a 20g P2NP reduction in a 3 liter flat bottom flask, with strong magnetic stirring which is going easier and easier while the Al dissolves.