Hg Amalgamation rates

[Vibrating_Lights]

Coul al be stored over period of a few days  in a dissolved meercuric solution if the Al was to be added to to a reduction over a few days.  Ie could the Al be left in the Alcoholic hg solution withut and degredation to the alumnin besides the oxids being removed. no further deterioriation.
VL_

[Flip]

Post 264143

(sYnThOmAtIc: "Re: Acidic Hg/Al amalgam", Methods Discourse) seems to suggest this is possible but says that it will substantially lower yeilds. Then again it says nothing about how long the Al/Hg could be kept so i'm still lookin for ya man.

[Flip]

Actually I think I misread... in this rxn you have to balance the al breakup with the drip rate.... this suggests that the breakup is not controlled by the drip rate as if the nitro was breaking up al.  Through my basic newbee logic I conclude that the HgCl2 breaks up the aluminum as well as removing Al203 and so once the amalgamation has started it can't be stopped and the nitro/ketone should be added before it's done. Wham bam thank you mam. That's what I think anyway

[Vibrating_Lights]

swim was thinking of havin a 10 gallon buchet with 1 gallon of ketone and arounf 3000 ml on nitro with 5 gallons of Meoh and having another buchet with Al/Hg and transfering the al as it was consumed  y the nitro(Lt already mentioned that) rather than adding the ketone as it was consumed.  reaction could be kept at toom temp..  Once the al is amalgamated does it degrase any further without reacting with the meoh that the Al was amalgamated on? How long can amalgamated al be stores.  there is H2O inthe tincture that the HgI is made from. bY the WAy HgI Kicks ass
VL_

[Osmium]

Don't do that. For this reaction you want a surplus of MeNH2 reacting with your ketone, not a huge amount of ketone reacting with nitromethane with methylamine as your catalyst.

Don't reinvent the wheel. Don't make things more complicated than they are. Just follow the procedure. There are reasons why it is done the way it is done.
I'm not fat just horizontally disproportionate.

[Osmium]

Thick Al/Hg can be stored for a while for several hours when water is absent. I wouldn't try that with Al foil though.
I'm not fat just horizontally disproportionate.

[Flip]

Wait, once again my obscure newbee logic has confused me...
I thought that the HgCl2 broke up the aluminum and that all nitro did was sit there and look pretty like reduced nitro or methlyamine and make stuff all hot and bubbly. Does the nitro also break up the Al?

Also I think i found an answer to satisfy vl_'s ?.  The storage time (amalgamation rate) will be dependant on the medium in which the amalgamation is kept.  Alcohols that are strong proton donors will make the amalgamation run faster, and weaker proton donors, slower. 

Those of you who have read the second part of this post are probably thinking, "Wow! That Flip is a pretty smart guy!" Do not be fooled... refer to

Post 264499

(terbium: "Re: ETOH and AL/hg", Methods Discourse). Never underestimate the power of TFSE.

[Chromic]

Amalgamation rate refers to how fast the aluminum displaces the mercuric ion from the solution to form a mercury coating on the foil. It has nothing to do with how long the amalgamated aluminum will keep.

Amalgamated foil would likely be stored a anhydrous non-polar aprotic solvent like ether in an air-tight container... if stored any other way, I don't think it'll stand a chance of keeping. (just as you must store any reactive metal away from oxygen and/or water and under a non-polar solvent)

To acheive highest yields, one would add the nitro first, then add the ketone (or at the same time...) because a high methylamine to ketone ratio is desired. The nitromethane provides oxygen to "burn" the aluminum foil, the nitromethane is what is responsible for the reaction being so exothermic. If you were running MeAm and ketone, you'd likely be able to get away without a condenser.

I don't understand why people want to scale the nitromethane approach or the oxone approach. They're ideal for small scale reductions, but are not well suited for large scale reductions... switch methods...

[Osmium]

> Would it affect the rxn Al/hg if an excess of
> nitromethane was added.. say if the synth calls for 20g
> and you give her 30.. would that cause a negative effect
> on the rxn???

Yes. Since the amount of Al present would be insufficient.
I'm not fat just horizontally disproportionate.

[Vibrating_Lights]

how about if 500m lnitro  wasa pplaced in the bucket with 1L Meoh and the activated al was added intil all the 500ML MeNo2 Had reacted Then the 1000 gm ketone added and the other 300 ml nitro along with some more MeOh. Then Activated al is added at a rate to maintainrefuly adding more MeOh as nescsary for proper stirring .that way there will be Me Am present when the ketone hits to for the imine.  then more amine will be produced as the imine that has already being produced is being reduced. 
VL_

[terbium]

Yes. Since the amount of Al present would be insufficient.
And to elaborate on Osmium's reply: This is because there are two reduction reactions being performed by the aluminum

1) reduction of nitromethane to methylamine

2) reduction of the methylimine (formed from ketone and methylamine) to MDMA.

[Vibrating_Lights]

theoreticly if one were to have ketone in meoh with activated al,  and was to gas MeAm into the solution the al would only reduce the imine produced and not the ketone alone back to the alkene before it had a chance to condense.
VL_

The original question though how does using thicker al affect the ammount need to reduce the O atoms,  or does it just provide a slower rdn rate.  Swim has herd that the weight of al/mole to be reduced is didderent than when using foil.  WIll 27gms of .005 foil reduce 20gms of ketone and 20 nitro the same as 27gms of foil would.
VL_

[isohuman]

If one were intent on doing it that way, wouldn't it work to add the ketone, nitro and the hg salt in the same bucket, and just toss in regular old unactivated aluminum over the course of the reaction.  Iso can see no reason why the new aluminum would not continue to amalgamate.

[Vibrating_Lights]

The Hg forms complexes with compounds. 

[Flip]

We all know the textbook definition of amalgamate (to bond a metal w/mercury), but chromic seems to be suggesting that its the nitro and NOT the HgCl2 that is responsible for the Al breakup. And so I am still confused.  I was under the impression that the HgCl2 broke up the foil as well as removing oxidized aluminum. And ether being a (strong?) proton donor would cause this to happen quickly.

I guess the easiest ? to ask to obtain the info I want would be will an hg/al amalgamation in an alcohol break up into grey sludge if nothing else is added (no nitro/ketone) or will the Al2O3 be the only breakup?

[noj]

Quite simply, the Hg removes the Al2O3, the oxidized Al. Once that is done, reaction will stop UNLESS the Al oxidizes again, in which the Hg will remove that again, continually until no more Al is there, or the Hg is depleted (reacted).

If the Al is unable to reoxidize from the oxygen in the air, water, etc, it will stay in the elemental Al state. This is an unlikely situation for the majority of the bees here, without the proper equipment.

The nitro will not react with Al2O3. So the only way to get it to react with the elemental Al is to remove the Al2O3 oxidation with Hg.

Since the nitro DOES react with elemental Al, it will destroy (react with) it. But only if there is no Al2O3 preventing its contact with it.

In conclusion, to keep elemental Al from reoxidizing you will need to keep oxygen from the equation. Keep it in a nonpolar solvent will help, but it won't be permanent. The thicker the Al, the longer it will keep some Al available.

Chaque un à son gout

[Bwiti]

In my dreams, cut up soda/beer cans work great, and using ethylamine/methylamine instead of nitromethane/nitroethane produces less heat. If you plan on scaling a synth up, be sure to have a good overhead stirrer.
  Btw, adding more Al/Hg than the synth calls for won't hurt anything, will it? Peace!
  Love my country. Fear my government.

[Flip]

Thanks for the explanation noj,you've enlightened me.

[Osmium]

No no no!

An amalgam is an alloy containing Hg having the interesting property of overvoltage. This means the Al wants to react and dissolve badly with alcohols and water producing H2 in the process, but this reaction is greatly hindered (NOT completely stopped, just slowed down a lot!) since H2 doesn't like to be produced on Hg surfaces.

When there is anything reducable around, like a nitro compound or an imine the Al can dissolve without having to produce H2 gas, and it readily will do so.
This reaction involves electron transfers between the reaction partners, which is just another way of saying the Al is dissolving and gives up its electrons to the Hg which in turn transfers them to the organic reactand to be reduced. It's not the Hg salt that breaks up the Al. If there is nothing around to be reduced then the Al can't get rid of those electrons, and it will not dissolve. Al/Hg in an inert solvent like hexane or toluene should be quite stable for a while. Al/hg will react with oxygen because Al is a very reactive metal which is only protected by its oxide coating (passivation), once that coating is removed it will oxidise in air, but that is usually not an option when covered by a solvent since O2 solubility is very low.

The solvolysis reaction with an alcohol will be very slow with thick Al because it has a much higher Hg loading on its surface and a much lower exposed surface area than foil.

Al/Hg in a pure alcohol: only very slow dissolving via solvolysis. Greatly enhanced by water presence (since Al2O3 formation is very exothermic and the driving force) and change to basic pH

Al/Hg in water: exothermic, will heat up considerably and might eventually react violently

Al/hg with nitro in alcohol: very exothermic reaction due to water formation, and since nitro is hot stuff  

Al/Hg with nitro in alcohol containing considerable amounts of water and a base: let's not go there, runaway reaction with foil, very exothermic with sheet

Al/Hg with an imine in alcohol with a littlewater: rather slow and gentle reaction

Foil reacts much faster than sheet!

Don't try to tweak the reaction too much and reinvent the wheel! Al/hg works, in up to 90% according to the literature and some bees experience. And when done without haste and with thick Al it can even be very volume efficient.
I'm not fat just horizontally disproportionate.

[Flip]

Wow! That's a damn good answer, very specific. Too many people on this board, including myself, know too much about the processes themselves and not enough about the science behind it. Those kind of specifics are what really strike my interest in this feild. Thanks.