NOTES ON THE AL-HG REACTION:
1) If using a round bottom flask for this reaction, a water bath can be used to heat the reaction
flask. Flat bottom works better though as it gives a good platform for the stirbar to spin on. If
using a round bottom flask make sure to use an egg shapped stir bar and not the long rod-
type stir bar.
2) Make sure to add more MeOH through whichever neck if the reaction begins to get thick and
doesn't stir as well. Also, the flask may be picked up and stirred by hand occasionally if this
helps to get the mag stir bar going.
3) If reflux starts to get out of hand, slow down the addition rate of the ketone / nitromethane
solution.
4) Add as much MeOH as it takes to keep the aluminum covered during the addition cycle...
Much MeOH is lost due to evaporation even with the condensor circulating ice cold h2o.
5) When the addition is done, try to break up the aluminum as much as possible (by hand
swirling?)
6) Cool the condensor to ice cold before the addition is begun to ensure higher reaction yields.
7) One states he adds up to 100ml MeOH after the addition to ensure the aluminum doesn't
sludge things up too much and the reaction keeps stirring well.
During extractions, shake as long as you can for as long as you can.
9) Blue_Diamond says - best runs were seen when the addition was fairly fast and the reaction
ran at a hot reaction temperature.
10) The reaction is refluxing too quickly when bubbles can be seen forming and rising inside
the condensor.
11) When washing the toluene / product layer with 4 or more water washes, if the 4th water
wash isn't clear, keep doing water washes until h20 is CLEAR. Have to let the h2o layer
sit a while to let bubbles get out which make it look cloudy. Water should be as clear
(after last wash) as it was before being put into the separatory funnel.
12) Methyl Man says - to add incrimentally enough MeOH during the reaction so as to keep
it stirring well at all times.
13) Methyl Man says - "you HAVE to make that puppy run HOT"
14) Get a high output water pump for condensor water circulation here to cool this hot reaction
down sufficiently. "Reaction should be really humming when you've dropped in 20% of the
nitromethane / ketone / MeOH mixture. Flask too hot to touch for 1/2 second. Should still
be this hot when the last of the nitromethane / ketone / MeOH is dropped in.
15) Bizwax says - it wouldn't hurt to let the reaction run 6-8 hours to make sure it is completely
done.
16) Water IS needed in this reaction so do not dry MeOH before using.
17) Coffee grinder = Black & Decker "Coffee Mill" (cat # CBM-1 Type2)
18) Stirbar = 3" egg / teflon coated
19) Use at least a 150 gph water pump for condensor water
20) The condensor water should always be super cold
21) Methyl Man says - "watch the vortex, if no vortex is noted then add incrimentally up to
~ 100 ml MeOH to help stirring commence again."
22) Methyl Man says - use a 400 mm Allihn for reflux for this reaction.
23) High-oleic safflower smokes when heated to a high C the second time, but its ok to use
the first time.
24) Methyl Man's latest advice on running this reaction (as of aug 6 '00):
- add the ketone fast right from the start 2 drops a second
- make sure the whole addition takes only 30 minutes...no more
- this gets the reaction DAMN hot
- reflux should be dripping so fast its almost POURING down
- use a 2L flask...NOT a 1L
25) To avoid MeAm smell during the reaction, run a tube or hose from the top of the condensor
to a 3 N solution of HCl. This will turn any gaseous MeAm into its HCl salt and eliminate
any aroma
26) When adding extra MeOH to help keep the reaction stirring, make sure to pre-heat the
MeOH to ~ 55-60 C before introducing to the reaction flask so as not to cool the
reaction contents too much.
27) Osmium says the al-hg works much better with 40% aquous MeNH2 as opposed to Methyl
Man's nitromethane version.
28) If using a fridge compressor / pump for the vacuum source, always cool it while in use
with a high speed fan blowing directly on it
29) Osmium says all the aluminum sludge must be removed before the ketone workup
(a/b washes / extractions) is done. If ANY aluminum sludge is left over it will TOTALLY
fuck up the a/b washes. If not sure that ALL the sludge is removed, then filter until
ALL THE ALUMINUM SLUDGE IS REMOVED WITHOUT QUESTION
30) MM says - the main things are
a) use Reynolds Wrap Heavy Duty Foil (THIS AND ONLY THIS EXACT BRAND)
b) use between 400 and 420 mg Hg salt
c) react the motherfucker DAMN HOT
d) make sure and keep the thing stirring the whole time...even if it takes adding MeOH.
e) after only 20% is added to the rxn. container, it should really be going HOT...flask too
hot to touch for even 1/2 a second and the condensor working furiously mad.
And it should still be that hot when the last of the goodies are dropped in.
continuing...about 5 minutes after the last drops have been added from the addition funnel,
the reaction should start cooling down...and at this point mm likes to start adding a bit of
heat to help break down the remaining aluminum
31) NEVER, EVER, EVER allow too much solvent (MeOH) to evaporate without adding more
during this reaction so that improper stirring ever occurs. A guaranteed DECREASE in
yield will result if PROPER STIRRING is not MAINTAINED at ALL TIMES .
32) Keeping enough methanol in the reaction mixture to ensure PROPER STIRRING is a big
determining factor in keeping yield % high.
33) Add 2-3ml dh2o to rxn. flask solution after the aluminum has initially amalgamated.
34)
a) Don't overgrind your foil in the coffee grinder - only a few seconds of grinding will do.
b) Be sure to use a big ass stir bar - violent stirring will up your yields.
c) Let your NaOH solution cool to room temperature before using ( DCM boils at just
above RT ).
d) Also...let your aluminum react completely (dissolve?) after your ketone addition...it may
even take over three hours.
e) Also...afterwards don't skimp on washing the toluene / product layer with water. Extra
washes help remove any remaining mercury.
35) Baalchemist ran mm al-hg with...
a) 31g ketone
b) 25ml nitromethane
c) 50ml methanol
- all the above well mixed in an addition funnel
d) 750ml methanol
e) 400mg HgCl2
f) 33g foil
- all the above in a 2 L reaction flask
* - addition done at 2.5 - 3.0 drops / second. Addition is finished in ~ 20 minutes.
* - addition was finished while rxn. was still in strong reflux
* - refluxed for 3.5 hours when reflux began to slow down a bit
* - workup (washes / extractions) were done as usual with a little extra toluene
* - epsom salts were added to the toluene to dry...stirred for only 2 minutes.
* - toluene soln. then hcl gassed to produce 31g product
* - the reaction runs REALLY HOT at this addition rate but if done in a 2L flask
it has plenty of room to spare during the hottest part of the reaction.
36) Baalchemist and
others have done some great work and have reported in this file upping the starting
reagents and adding them quickly to get a 1g ketone = 1g product yield %. Other tips
included in this file include adding 1/3 of total nitromethane to be used to the rxn. flask
directly after amalgamation occurs but before addition of the ketone / nitro / methanol
from the addition flask. Others = adding a small bit of h20 (2-3ml) to the reaction during /
before the addition and another is to reflux post addition completion for 4 hrs. or so. Make
sure to reread this file and ask questions.
37) Oct 3. - baalchemist says - preloading with nitromethane (1/3) gains nothing in yields in
quantities up to 50g. Frost agrees with baalchemist in this point and adds..."if no external
heat is available, and only stirring is available, it will help to break down the aluminum
better by adding 1/3 nitromethane first...which in turn will make for a better yield %...but this
is ONLY if no external heat source is available to aid the reaction post addition peak temp."
Bizwax agrees with baalchemist and frost on all these points
38) Reply to a pm to baalchemist - he says he gets better yield in the mm al-hg by speeding up
the addition rate. He says that mm has said (of his own original tek) that with the slower
addition of the ketone / nitromethane / methanol mix (30-45 min) that the aluminum foil is
too far broken down by the end of the addition...thus resulting in less product yield %.
Baalchemist says he increased the size of the rxn. a little and increased the addition rate
and now gets 31g salt from 31g ketone. Says he always worried about the volcano factor
during this reaction, but has found that as long as the condensor is super cold and if one is
is using a rxn. flask with plenty of headroom that faster addition can be accomplished with
no worries.
39) In a reply to a pm , baalchemist says - "been getting 32g salt from 31g ketone like
clockwork lately. I use 31g ketone, 26 ml nitro, 50ml MeOH - well mixed, added to
925ml MeOH, 125mg HgCl2, 37g foil. 3 drops a second addition rate usually does it.
Sometimes an additional 20-40 (or a little more) of MeOH is added to help stirring.
40) Baalchemists modified Al - Hg -
thread titled = "Baalchemist's modified Al/Hg"
- 36g Reynolds Heavy Duty in 1" squares ground for ~12 seconds
- placed in 2L flat bottom with magnetic stirbar
- add 100-120mg HgCl2 to 950ml (or a little more) MeOH, shake ~30 seconds, set aside.
- 31g ketone, 26.5ml nitromethane, 50ml MeOH placed in an addition funnel and mixed well
- add the HgCl2 / MeOH to the 2L with the foil and stir on 10 for 5 minutes
- attatch condensor and addition funnel
- then add 5lbs ice to the condensor circulation water
- after 5 min. stirring, turn stirrer off to check for bubbles coming up to surface
- if you see just fizzing, stir again for 3 min. then check for bubbles again
- If bubbles (not fizzing) are present, turn stirrer on 10 then begin the addition
- drip rate of 2.5 - 3.0 drops per second. (the faster the better here)
- might add an additional 75ml MeOH during the reaction to keep it stirring effectively
- addition should be complete in about 15 mins. foil is 1/3 - 1/2 broken down
- contents are grey with a noticeable blue hue to it
- when reaction reflux slows, add enough heat to keep it at reflux for 3.5 hours after the
addition and no more ("no more" time or "no more" heat ?).
- keep it stirring while cooling, then add 400ml toluene, then slowly add base solution
(300g NaOH in 825ml H2O).
- stir this for 30 minutes
- remove toluene
- add another 200ml toluene
- stir for 20 minutes, remove toluene
- extract with prolonged stirring with a last aloquat of 100 ml toluene
- combine toluene extracts and dump in 35g dried Epsom Salts
- stir for 1 min. - then let sit for 2 minutes
- then gas for 31-33g yield
- faster addition + less HgCl2 = higher yields
- also make sure you have a damn efficient condensor
- put a wad of paper towel in the top of your condensor to keep hold of stray vapors
41) Baalchemist's AL/HG twist = thread name
- 55g foil nuggets 50/50 mix of 1" square and 2" square
- in a 2L flask a 50/50 mix of 99% IPA, and MeOH were placed along with foil
- after making sure this vol of liquid would stir, 120mg HgCl2 was added
- stirring, amalgamation occurs and a condensor is fitted to the top of this amalgamation
apparatus
- 50g ketone, 40ml nitromethane, 50ml MeOH
- after 7 minutes, amalgamation was apparent and addition was begun at 3 drops per sec.
- addition was complete in ~15+ mins. and addition heat was added to reflux for 3 hours after
reaction begins to slow.
- stop, let cool, then transfer to a 3L beaker for basificaiton.
- 825ml H2O and 300g NaOH was then prepared
- 500ml toluene was added to beaker with stirring, the base solution was added slowly.
- stir 30 minutes then remove toluene
- do again with 200ml toluene
- do again with 100ml toluene
- combined toluene extracts were washed with H2O 3X
- then toluene extracts were washed with a saturated brine solution (NaCl water?)
- this was gassed for a total of 52.5g salt
- Methyl Man's comments on the above reaction after doing it himself..."did your ratios
and found the amount of NaOH you use is NOT enough to dissolve the aluminum. It
made for a sticky ugly dirty extraction process. 300g NaOH in 825ml H2O is just not
enough. I'd suggest doubling the amount used in the MM write up which would be
1500mL of 35% NaOH or something close to that. Also, I was timid running the addition
that fast and would feel much more comfortable running it in a 3L or 4L flask."
Baalchemist says - he "carefully pours nitro, MeOH, then ketone into addition funnel when
making the mixture." these layers of chems sometimes separate so this may be a fairly
important step he's mentioning here.
42) Make sure that the NaOH is a little below room temperature before putting it in and that a
condensor is placed on top of the vessel just after the NaOH solution is added. Methyl Man
says about this step..."if basification is not done cautiously and slowly, the goods may get
all pouty and decide not to cooperate later during crystalization." SOOOOO the lesson
here is, again, to ad the NaOH solution slowly.
43) When doing the Al-Hg addition step, have a high speed fan pointing at setup at all times.
This is to be used if rxn. starts to get out of hand and needs to be cooled quickly. If fan is
used a wet paper towell or piece of cloth should be placed over the condensor so the air
current won't blow any uncondensed vapors out of the condensor. Make sure rxn. setup
is well braced though so as not to be blown over.
44) MM says "at the 55g aluminum scale, the al-hg reaction, one 400mm Allihn reflux
condensor ISN'T enough."
45) MM conjecturing on the nature of the al-hg reaction while ultimate rxn. conditions are still
being researched (November 16, 2000)
"One key factor - and Baal and I are in agreement on this - is that there is a 'spike' in the
middle of the amalgamation process ... a place where it gets hottest based on how fast
the ketone had been added up to that point. Assuming a decent rate of addition in the
beginning, like around 2 drops per second, with experience one can take the reaction to
the brink of volcano-ness --- the spike --- and then stop the addition for a minute, let it
calm down, and then from that point forward it is less subject to go nuts and one can
speed up the addition significantly (with caution of course). Yields are ABSOLUTLY
LINKED to the rate the ketone goes in verses the rate of amalgamation. In other words,
if the aluminum looks mostly reacted, and you still have half your ketone in your addition
funnel, you will get a shitty yield. This is not news but it bears repeating because it makes
all the difference in the world ! "
46) When doing the addition part of the al-hg, make sure the glassware is setup so that the
heat / stirring source can be removed. This is so that if the reaction starts to erupt due
to the addition being done too quickly, the stir source can be removed out from under the
glassware (which stays suspended) and a pan of cold ice-water can be brought up
underneath the reaction flask to cool it off quickly. One of those platforms that crank up
and down would be an ideal platform to set the heat source on. This would allow the heat
plate / stirrer to be cranked down and removed quickly.
47) Baalchemist's entry on a hive al-hg thread:
"SWIM uses no more than 100mg of HgCl2 on reactions as high as 60 grams (al?) in a
2 L flask. SWIM cut the HgCl2 amount back because it slowed the reaction pace
(amal.) down and the intensity to a more workable pace, thus doing larger scale
reactions (60g) in that same 2L flask that was used for the 25g reactions. SWIM has
used as little as 40mg HgCl2 in a 60g reaction, but it takes much longer for the initial
amal. to kick in, but finishes like a champ with no probs. Definatly not one for the
newbees"
Take from this that maybe 100mg HgCl2 should be could be a good starting point
48) Nother exerpt from a al-hg thread from Baalchemist:
"Al foil (after being grinded in a coffee grinder) should not be too tight or it will adversely
affect reaction. This reaction's success depends on OPTIMAL stirring conditions.
49) Baalchemist's exerpt from an al-hg thread
"SWIM uses a lot less HgCl2 than MM, about 100mg. Try 2-3 drops in the beginning until
it refluxes hard and is about to blow, then
stop for a minute or so, then start addition again as fast as possible SWIM ran one the
other day with 30g+ ketone in, 34 out. That size reaction seems to produce the highest
yield % here.
50) RollWitMe writes of getting 22.5g product salt using ketone he usually gets 17-19g product
salt from by making a small variation in his usual al - hg reaction. He added .4g HgCl2 to
750 ml MeOH and stirred and heated it until it was boiling...then let it stand and cool to
around 55C. Added 27.5g aluminum and got what he describes as instant amalgamation.
He then immediatly began dripping in a mixture of 25g ketone / 20ml nitromethane /
50mL MeOH at a rate of 3-4 drops per minute. Workup was done the typical way, 35%
NaOH , extracted with toluene, washed 4x w dh20, 1x with saturated NaCL dh20.
Rotovaped down to 100ml, dried with 30g epsom salts...gassed, filtered, washed, dried.
He says he feels his extra product yield is due to adding ketone/meoh/nitro mix to an
'already pissed off' boiling amalgamation.
51) Stuffing coarse steel wool into a reflux condenser makes it work much more efficiently
during the initial addition and the subsequent refluxing that takes place in the al-hg rxn.
52) Tip from DiEthylEtherMan ... he does 3x al-hg with a 700mm with 15-18 minute addition rate
and his rxns. go 1/3 to 1/2 way up his condenser.
Tip: "after your 3 hour reflux with your al-hg ... let it cool but keep the stirring going. Turn
off heat 30-45 minutes before...after it cools remove the condensor and basify right
in the same container with the stirring still on high...this is how I've been doing it and
every piece of aluminum breaks down...the solution turns almost like a dark dark
blue / black color (thick) with no al floating around.
53) One bee writes of his theory that the al-hg reaches a bad spike in the middle when the
addition is done to a RT aluminum suspension because starting out cold
the ketone doesn't react well only slowly building heat as the addition continues. When it
eventually gets hot enough, all that unreacted ketone starts to react and then things really
get out of hand with bubbling through the condenser and shit. If the amalgamated
aluminum suspension is heated before the addition is started, the ketone being added
reacts immediatly and as it is added, thus, aleviating the risk that a ketone build-up will
occur which subsequently causes a large reaction temperature spike. Sounds good.
RollWitMe writes Feb. 19, 2001 - Add .4g HgCl2 to 750ml MeOH. Stirred and heated until
boiling. Let cool to ~ 55C. Added 27.5g balled aluminum foil. Basically instant
amalgamation. RWM knows that because the aluminum is floating on top and the solution
starts to turn grey. Immediatly started droping Ketone / Nitromethane / MeOH (25g / 20ml
/ 50ml) at a rate of 3-4 drops per second. A rxn. that he gets typically 17-19 g from he got
22.5 g salt.
54) Idea on how to cut foil strips:
Use a ruler or other straight edge on top of the foil leaving an inch exposed. Pull the foil
starting from the corner furthest from you and pull against the straightedge. You'll tear a
perfectly straight strip (well, mostly after you get the hang of it) . This cuts the foil prep
time down by at least 70% and you don't have to fuck up a pair of scissors doing it.
Another idea is to use a long straight edge (long metal ruler) but use an exacto knife all
on top of glass to cut the strips...then put the strips together and use a pair of scissors
to cut them into 1" squares.
55) Yet another saying that for this reaction to work well...it must be stirred VERY well. This
gives rise for the need for a really strong stirrer / hotplate combo
56) Some of the large use a paper shreader to create their foil strips first then cut
again, then grind the foil sheets till they are the size of rice grains.
57) Red water after the al-hg reaction is a sign that the ketone used in the rxn. was dirty.
58) terbium has said that a Friedrich condenser is more effective at holding back a strong
reflux than a Liebig or Allihn condenser.
59) Baalchemist says to use a 2.5 inch egg shapped stir bar with the al/hg. One must shave
the ridges near the center a little at a time until it fits through the 24/40 glassware joint.
Baal also says that hex shapped stir bars suck in sludgy environments.
60) terbuim has stated that a Friedrich condensor is much better at holding back a strong reflux
than a Leibig or Allihn condenser. A Friedrich condensor, though, should NOT be used in
a vacuum distillation setup
61) DiethylEtherMan...states that in the al/hg, it is ok to use only 200 mg HgCl2 as opposed
to using the 400 mg HgCl2 most write-ups suggest.
62) DiethylEtherMan...states that Toluene is getting harder and harder to get these days and
a great substitute would be Xylene. Just make sure to chill it before any gassing is done.
The only drawback he states is that uxing Xylene makes it take longer for the crystals to dry
completely but that this really isn't a problem.
63) Chromic states that a 400mm Allihn is the appropriate condenser for the al-hg...that a
250mm Liebig just won't do it.
64) noj says that stuffing steel wool in a condenser DEFINATLY helps to contain a reflux.
END OF NOTE SECTION FOR THE MM NITROMETHANE AL-HG
We hold these truths to be self evident.
