Al/Hg Nitro Synth regarding flask size ???

DjTime · Chemical Dj

I used to use a 2L 3 Neck RBF as the writeup called for, However I switched to a 5L 3neck RBF and use it so i can have extra headroom for the reaction flask. I have never had shitty yeilds. And I never failed, not one reaction. Until I switched to the 5L and the first one was like a 30% yeild and the next one was in my mind failed i got like a 5% yeild.

Can anyone tell me if for sure that changing the size to a 5L flask would ruin the reaction? Thanks.... Peace Out

IndoleAmine · Dreamreader Deluxe

Most likely you will have to change Al foil thickness, stirrer size/speed and/or amount of reagents used by the factor 2.5 to arrive at the same conditions like you had with a 2 liter flask.

A good reason for your almost-failure could be that you are used to perform the rxn in a 2 liter, and have unconsciously perfected your way of adding ketone, preparing foil etc. specifically for that flask size and proportions of reagents.

Try scaling up to 2.5x the amount, and also use thicker foil (or harder nuggets?) and longer rxn time, this includes more time for amalgamation.

With a bigger flask, the main differences are 1) the ratio surface/volume and 2) the effectiveness of cooling - this could maybe make the MeAm escape too quick when a larger flask is used....

i_a

DjTime · Chemical Dj

I think ill just go back to the good ol' 2L it worked, no reason to fix what's not broken. I thought maybe having more headroom would be better in case of a runaway like what happened earlier. But yeah back to the 2L..... Thanks alot. And as always Peace out!!!

DjTime · Chemical Dj

Went back to the old way of doing things where SWIM was geting 18-21G of product. That made no difference. Still getting 4-5 grams. Everything SWIM uses in the Al/Hg reduction is 99% pure except for the ketone he makes which he has no clue the purity of that. However the p2p he guessed is the only thing that could be the problem. SWIM follows the methylman writeup to the T. His foil is correct and his nitro, and HgCL2 is pure for sure.

Can any one else give SWIM a reason or pointer as to maybe why his yeilds are low besides that the p2p may not be legit?

ApprenticeCook · DILLIGAF

deleted repeated post.
The al/hg is a fickle beast somedays.... but.... how do you know everything your using is 99%? tested it?
Your ketone should be distilled, twice disitilled is even better, so once this is done, the purity level is high enough to use in the al/hg.
Homemade HgCl2 and supermarket aluminum foil cannot be said to be 99%...

-AC

DjTime · Chemical Dj

your right alum foil isnt tested. however HgCL2 is aldrich, 99% pure and not homemade. SWIMs ketone is distilled twice. It looks and smells just right to from what im told. Just dont get it. Got the procedure down firm. SWIMs never had a problem with it before. Guess he'll just have to try again untill he can pinpoint the screwup. Peace Out......

bio · Working Bee

Not sure what the 2L scale is (25g ketone?) but a larger flask is, from experience better, given two assumptions with proven foil.

1) Drip rate is fast enough to produce a very
vigorous reflux almost to choking.

2) Completion of addition nearly coincides
with end of the aluminum.

In a 6L flat bottom one 24/40 neck anywhere from 40-70g works fine. Anything more and the condensor (5 bulb allihn) chokes too much with possible disastrous results (lost about a third once). This is with near freezing condensor water, flask directly on the stirrer/hotplate, a 4X3/8 magnet as fast as it can spin under control and heat added as soon as the reaction begins to subside.

Your problem is most likely the foil if the ketone is prepared exactly as when you had good results. The Al is completely consumed if done correctly.

DjTime · Chemical Dj

it always is consumed tottaly. SWIM never had any chunks of Al left over. I never have to add meOH to thin it out. It's a very pourable solution with no prolems. Very light grey color with slight blue overtone like the writeup suggests it should be.

Thanks for the suggestions everyone. SWIM is going to attempt it again. After this SWIM needs to get another batch of ketone ready so we'll see after that. Ok off now. Peace Out.....

Soap · Fri Apr 08, 2005 8:14 am

the largest flask swim can use is a 500 ml 3 neck rbf. what amount of reagents would work best? if swim had to guess hed say 1/4 of the usual amount ( 6.25g mdp2p etc) should he just buy a larger flask? hed prefer not to...

DjTime · Chemical Dj

I say theoretically you could scale down by 1/4 however M.M. did this as an exact science just to get the half scale right. So maybe not. I say buy a larger flask and do things the right way unless you have a degree in chemistry and you know what your doin. Peace Out......

bio · Working Bee

A 500ml flask can react 100-150millimoles without a problem if using premade MeNH2 and imine with thicker Al. I've done this using only 1.2Al equivalents with yields at 80%molar, That's base not salt.

You might try this also under a little pressure (1Atm) as no MeNH2 is lost so it also can be used in small excess.

There is a short write up on the old Hive board I did on this if you are interested. If you can't find it I'll dig it up for you.

Nitro as amine source insitu is a good method but has inferior yield and is harder to control than the aforementioned. It's not really suited to larger batches unless you have a nice tank laying around.

Also check the Hive archives for a thread by Abacus on processing 1mole ketone in a day using Al/Hg Nitro as it is also much more space efficient than the MethylMan.

Soap · Sun Apr 10, 2005 8:11 am

swim dosnt think thats its worth the risk to not use the usual 2l flask. swim will spend $40 on a 1 neck flat bottom 2l flask. swim has a clandsen (sp?) adpater to atach to the top for an addition funnel (only 125ml, but it can be refilled???) and a 300mm allihn condenser. sound good? most of the write ups swim has seen call for a 2 neck flask, is it worth the extra money for the 3 neck?

bio · Working Bee

One neck works fine also, just add the reactants through the condensor. A 6 bulb Allihn is about minimum with under 5deg water circulating.

bio · Working Bee

..............Homemade HgCl2 and supermarket aluminum foil cannot be said to be 99%..............

Al foil is series 1000 alloy which is 99+% depending on the particular alloy.
http://www.matweb.com/search/GetComposition.asp has some good info.
Granted, theword foil sure doesn't mean its 1100 H-14. H-19.

Surprisingly, to me anyway, the common soft Al is usually 1000 series alloy which is all 99% or better. Surprised

brain · Linguist Extraordinaire

my Al foil (from supermarket-everyone !! ) contain couple % of Si metal !! when add it to HCl - black powder is on bottom... do you have that kind of problem?