Scale-Up on Al/Hg is not that easy...

[raffike]

Raf has done few Al/Hg successfully with 70% yields.These were using 50-60 grams of ketone in a run with around 25 grams of 0,1 mm Al from pie pans.Then he tried to scale-up to 90 grams of ketone and 45 grams of same Al and this is where it got wierd.One run started very fast,Al got coated with some thick layer and bubbles that evolved were upto 0,5 cm in dia.Surely we knew that this couldn't be a normal metal dissolving reaction.Yield from 100 grams of ketone was 25 grams.Second run with 90 grams of ketone and 45 grams of Al started also very fast,boiled over when raf left the room for a second and when vessel was cooled to 55 C,the reaction stopped,Al coated with some wierd layer.Yield from 90 grams of MDP-2-P was 7 grams.Wasted about 190 grams of very good quality double distilled ketone to realize that scale-up isn't as easy as multiplying reagent quantities with 2.Raf thinks that it would have worked with let's say 0,2-0,3 mm foil but he probably doesn't experiment with these quantities anymore and continues to process 55 grams of ketone in a run.

[GenericVersion]

SWIM finds half scale rxn (usually around 25g Mdp2p) to be the most efficent, up to 93% of theory ~25g final yield has been SWIM's personal best(snow white xtals before acetone wash)

raffiki have you tried using Al wire in your dreams, a good excess and also a bit too small to get "coated" just as long as you run the rxn in a 3L+ flask ( and add heat after the inital rush), expermenting with Al should yield some useful info regard size and shape of Al. most effective some have said to form a ring shape around a finger using Al foil, in a dream someone once tried an al/hg using 200g ketone, balled the Al tightly and stirred constantly added a bit of heat as things progressed and in the end through a VERY messey workup yielded 180g 83% theory, it is possible, however SWIM has a problem getting rid of that much through normal channels  a testament to the fact to not get above your means. one must always think of what happens next

[Organikum]

If it was not enough mercurysalt what was added to much NaOH or the sheets were fishy - can´t say. But as you describe the violence of the reaction from start there is no other possibility. (to fast adding of ketone perhaps).
And yes! Ablolute true! Reactions are not upscaleable by multiplying the reactands and solvents by factor X! Alone the fact that surface area of a flask goes up in the second potenz but content in the third (cubiccentimeter =cm x cm x cm, surface cm x cm) should make this obvious. Much less heattransferarea per molecule!

[raffike]

About 1 gram of Fluka +97% HgCl2 was used.Al was covered in denat ethanol and HgCl2 was added,let amalgamate for 15 or so,alcohol was grey and foil was surely amalgamated and bubbling a bit,when methylamine/NaOH mix was added,things got very violent,with 20 grams of Al foil upon addition of MeAm/NaOH mix,reaction proceeds with temperature slowly rising(about 1C/minute).Maybe there's just too much foil surface and runaway happens.Never had this problem with 20 grams of foil.
EDIT:Will try Al wire in future,thanks for a suggestion.

[Organikum]

Raffike, I didn´t say you´re to stupid to almaganate right, really not!
But thats the second point I spoke of: The reaction dynamics are changing in bigger reactions by the changed volume/surface of vessel relation. So the amount of NaOH necessary in a smaller reaction to keep it smooth going can lead to a runaway reaction if scaled up by simple multiplying the ratio of reagents. The overcooking showed that the this was running to fast, to hot, you´ll agree on this. Why? The factors causing this are limited.

How do you add the ketone/NaOH?
How much NaOH do you use?

GenericVersion, the Al-wire is very interesting! I was thinking on this by myself but didn´t try it up to now. The wire should be very pure if was used for electric installations thats how I got the idea.
May you share some experiences and what kind of wire was used (how thick)? This would be very appreciated!

[raffike]

Ketone was dripped in over 5 minutes or so.I can't see how this could affect rx.Roundbottom adds it all at once.Raf used 80 grams of NaOH mixed with 240 mls of water.130 grams methylamine.HCl in 130 mls of water was used.About 700 mls of denat EtOH was used as solvent.NaOH solution was poured into MeAm.Cl solution and resulting methylamine freebase solution was added to rx mix before ketone.Otherwise followed RoundBottom Os/BB writeup.

https://www.thevespiary.org/rhodium/Rhodium/chemistry/redamin.os-bs.html

[wolfx]

To Raffike :

I think you should scale up the foil thickness as well, so the reaction will not become too violent. Then the foil area is the same. Might take longer, though.

Foil thickness of 0.10 mm, 40 g ketone and about half that of foil ( 20 g or so ) looks adequate for me. If you want to scale that up 2X, try using 0.20 mm foil.

[RoundBottom]

i didn't notice that you were following my writeup until this post.

SWIM just did a 900mmol (160.2g ketone) version; everything was the exact same reagents as the last 300mmol (53.4g ketone -> 50.6g salt [yes, A/B'd and recrystalized in IPA]). the results aren't fully dry yet, but the bulk is already dry and over 140g (same, A/B'd and IPA recrystal) with some still to be checked.

in this reaction, the ketone was dripped in over 40m (not 100% certain of the addition time but thereabouts.)  it did run slower and a bit cooler than adding it all at once.  also, a new fredrichs condenser (as opposed to a 6 bulb allihn) was used this time.

ketone: 160.2g (900mmol)

MeAmCl: 182.3g (2700mmol, 3x excess)
dH2O:   182.3g

25% NaOH solution for MeAm liberation
NaOH:   108.0g (2700mmol, 3x excess)
dH2O:   324.0g

MeOH:   996.7g
HgCl2:  300mg
Al:     68g (2520 mmol, 2.

1133.2g 30% NaOH solution for basification
NaOH:   339.9g 
dH2O:   793.2g

[GenericVersion]

larger reaction, perhaps taking everything x2 even lengths should help, SWIM would have suggested to add the methylamine/naoh all at once and add the ketone over the course of 20-30 minutes after letting it algamiate only for 5-10 minutes, SWIY had too much Al at once over a large surface area having thicker Al would help as would slower addition, have you tried the same reaction over MeOh? I have a feeeling the results would differ.

Al wire used was stripped from the plastic jacket afterwords it was approx 1.5mm thick wound in a coil and proceeded to fit through 24/40 (not easy) it was all one long coil, large rxn with ketone added all over 10 minutes never ran away a bit of heat was needed to keep things at ~64-66C as things progressed and final yield stated above for the large rxn was after recrystal in acetone

[raffike]

Thanks RB,btw how thick was your aluminium?

[RoundBottom]

standard 'merican heavy duty wreynolds wrap.  run through a cross cut shredder and lightly balled in a coffee grinder.  the pieces end up about 0.5cm x 5cm before grinding.

[raffike]

Hmm...raf didn't nuggetize his foil,he just folded em around the finger to ring-shape,this might have been his problem.He'll try 50 gram ketone reduction again when he gets his hands on any.

[scram]

There are some trick-ass foils that claim to be al and have other crap like tin in them. I've recently found rolled foil hobby sheets at the hobby store that claims to be al and says = 0.005" thick (that's 0.127mm).  Its thicker than any foil I've seen and not near as thick as flashing. I'll contact the supplier next time I go to that store and get their name to ask for msds on the foil or purity composition. I think this size is perfect if its real al.

[GC_MS]

There are some trick-ass foils that claim to be al and have other crap like tin in them.

That "crap" is there for a reason. A collegue recently remembered me of the fact that Al-foil indeed contains a trace of Sn for a well specific reason. But off course, I forgot which one. All by all, you can be relatively sure that Al has to be the main component. In high school, my chem teacher told us that the purity must be higher than 99.9%, otherwise it wouldn't have the useability is has as we know it.

EDIT: Don't worry about Al/Hg problems, raffie. Read the chapter in TiHKAL about The Wise Man's trip to Brazil, and read how even He had problems with the thin Brazilian Al-foil