Al/Hg How big is big?

[Antibody2]

i've always heard bees pooh poohing Al/Hg because of its inability to scale effectively, what is this? fact or fiction.

case one)
Osmium's thick foil variation reported to scale to one mole rxns sucessfully in 2l glass

case two)
doctor??, a bee i used to know who gave me his HgBr2/Al/P2P synth. and it didn't have much detail ei the type of foil, it sounded almost as though he was using a solid chunck of Al to reduce P2P in kg+ quantities, he described a slow rxn that took days to a week, didn't seem to include stirring, think maybe he mentioned sloshing it around a couple times a day.

so anyways with renewed scruitiny of borohyrdides these days its time to reconsider BIG AL/HG. Looking ideas, precedents, modifications to existing rxns all welcome.

I'm thinking that viscosity of solvent will become an issue,possibly retarding ion exchange, neccesitating solvent addition, with Al the size and thickness of coins or maybe long rods that would extend the depth og the rxn vessel, with strong slow overhead stirring, not so much to stir the Al but to prevent suspendsion from settling. And last of all doing it in plastic garbage cans. I realize tyhat work-up will also be challenging but wtf where theres a will a way is soon in evidence.
"All those memories lost like rain..."

[Rhodium]

My opinion is that the Al/Hg with foil does not scale well (due to the exothermic nature of the reaction), but that reactions with Al sheet scales perfectly well.

[PoohBear4Ever]

Does the foil work sufficently well in 45-50g batches, or is another source desired?

PB

[Antibody2]

[Rhodium]

I believe they often use catalytic hydrogenation in those cases.

[DiethylEtherMan]

Dear AB:

Shit, industrial size is not my ball of wax...due to height restrictions, I cannot go too big. However, my grandmother is up to 8x (per MM) with great yields. Using 12L FBF, Sep, and a 1200 alhin condenser...addition in 55 minutes...heat on for only half an hour after reflux calms...let it go for another hour...total time including tone addition is 2.5 hours...or 3 hours, but hasn't seemed to make a difference...

 
If some of us were not so far ahead, the rest of you would not be so far behind!

[RoundBottom]

how about this.  why doesn't each person post their best run for different sizes of glass?  then if one looks promising, we can ask for details or a complete writeup.  i'm very interested to find out what the max a 5L setup can produce.

state glass size, method, addition time, total time (incl addition), ketone, results.

3L 3N FB, std 2x MM AlHg Nitro, 1h 10m, 4h 45m, 50g, 44.5g

[PoohBear4Ever]

[PoohBear4Ever]

How would you define a "good magnetic stirrer?"  SWIP just sent out for his hotplate/stirrer today, which produces 900wtt, sold for $500 new, and should have a 7x9 plate.  Sound adequate?

PB

[Rhodium]

Pooh: Sounds good, I hope the magnetic drive torque is strong also, and you have a  fantastic machine.

[PoohBear4Ever]

[Antibody2]

I'm a goof, anyways the more i think about the issue, the dumber i feel about starting this thread.

upon reflection, this is a math problem, one need only quantify known sucessful reactions to hypothesis the question i posed.

i went into my shop and weighed a 30x0.5x0.125" piece of Al 82g with asurface of 37.5 square inches

then i weighed a 30x0.5xwho-knows piece of foil with same surface weighs 0.3g

so the 1st will react 273X slower and all that implys

but it also seems so many other variables come into play that that kind of equation is over simplistic and could use a hand constructng a better way of calculating scalability, or the physics of scaling up takingh into acount solvent ratios, temperature, surafce area of rxn vessel/cooling and of course some idea of where critical mass is in the math.

or even more B&W, how to calculate how to keep a specified amount of reactants within a temperature range by math. can someone help figure that out? that's what i am really asking,
"All those memories lost like rain..."

[spric]

It has been a while due to lack of proper facilities lately, but scaling up was not tried too much.  In a 6L flat bottom flask with a football shaped stir bar(they work much better than regular bars, eh) 100.0g of ketone processed using a #12 stopper with a 24/40 1m alihn slapped in it.  Yield would vary from 75g to 82-83g after single re-xtal, but never more than that.  That damn condensor would fill half way up with yellowish liquid unless vented, but then of course addition was under 30min..  1meter longer condensors are fucking amazing, a well spent $200.
4:20

[PoohBear4Ever]

Sounds like a experimental method might be best.  If using a set ratio of chems and Al, one could start with a very small rxn (say 10g) in a 1L flask, then double (say 20g) in a 2L flask, triple (30g) in a 3L flask, etc., and observe the amount of kJ given off from each.  Take these numbers, and find the average kJ/g, the mean kJ/g, and plot a graph to get a better idea.  How you would observe the kJ is beyond my knowledge, but for some reason "calorimeter" comes to mind...

So, say if one had a 5L flask, would he/she be able to successfully dream a batch as small as 30g, then work their way up from there?  Would the increase in exposed surface cause problems?  What size/type of condensor(s) would bee favorable if one were to dream 80g in such a vessel?

PB

* spric, I could get ya a 1200mm allihn for $140 new.

[RoundBottom]

spric, is that ground aluminum foil, aluminum wire, or aluminum sheeting/flashing?

SWIM has ~50mL (~56g) "known good" ketone and is willing to try a slower, thicker Al route, but using MeNO2, and report the results.

can SWIM have suggestions, specifically to amounts of Al, MeOH, HgCl2, MeNO2, suggested addition time, and expected reaction time.

SWIM has 1L, 2L and 3L RB flasks, with 1" and 3" egg bars (the 3" won't fit in a 24/40 neck though), a 1L mantle, the usual gear.

[PoohBear4Ever]

Read the ratios in

Post 223099 (missing)

(PoohBear4Ever: "Re: A Compilation of Documents", Newbee Forum).  Close fit?

PB

[RoundBottom]

well, that's a 2x MM AlHg Nitro. 

what SWIM is interested in doing is Osmium's

https://www.thevespiary.org/rhodium/Rhodium/chemistry/osmium.alhg.txt

but with nitromethane, like

Post 221621

(abacus: "Thick Al and nitro success", Methods Discourse). 

someone (rhodium?) had a post with a ratio of Al:ketone:MeNO2, but i can't find it   . 

i guess i'll just watch abacus' thread play out for now.

[Rhodium]

didn't post anything about that at least. Should narrow down your search.

[PoohBear4Ever]

If one was using flashing, what would be the prefered dimensional aspects of the pieces of aluminium?  Just 1" squares, or perhaps a "U" or a "V" shape?

PB

[Osmium]

Doesn't matter, as long as they aren't too big to be stirred.