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another question

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armageddon:
One thing that came into my mind: is it essential how the Dean-Stark is operated? While thinking about why SWIA isn't able to achieve high yields with this method, I realized that there are two ways of tapping off:

1. In a way that allows the FD top layer to fall back into rxn flask, i.e. tapping off as much water as is formed, minus the amount of FD that distills too - the FD top layer inside trap stays the same size all the time.

2. Such that the formed FD is continuously removed from the rxn, or better said tapping off same amount like  FD that distills over - the FD layer gets thicker and thicker, while the amount of water in trap decreases constantly.


 - Now which is the right way to do, Zealot (or Antoncho)? My guess would be the second one, as it seems to allow for a smoother temp. control - and after all, this is the purpose behind it, right?

Thanks for your help!

Greetz A

armageddon:
As long as nobody is able to reproduce the results Antoncho posted (this unfortunately includes SWIA, although he tried it numerous times, with highest purity reagents, exactly same amounts, appropriately sized glassware and the utmost care to do good lab work - 55% yield!), I am tempted to believe the >92% yield are a myth, too.

(sorry to say that Antoncho; I really would've loved to say otherwise, but all facts speak against it! What would be a motivation for writing such a bullshit - the reputation? Can't be - as it doesn't get better by posting exaggerated yields!? Wanting other bees to test out your theory? Then you could've said that, too - there's enough experimental data about unsucessful NH4COOH leuckarts using traps. Or maybe what you wrote is true; then this would bee the right point to give a bit more details about Zealot's work!!  :( )

...And please don't come and say that Zealot forgot to separate unreacted ketone from amine product! Because I don't see any comment about their separation; you just mention the steam distillation of crude "product", but did you realize that every unreacted ketone will steam distill, too?? And that the distillate mustn't only be extracted with nonpolar, but also further purified via a/b to get the pure amine? That if this isn't done, a healthy amount of phenylacetone/amphetamine imine forms, as soon as crystallization is attempted and the solvent dried for that purpose?

That would be the only explanation to me about the big differences between Zealots and other bees yield (which you calculate from amount of assumed freebase, not dried hydrochloride or sulfate)!



So to prevent other bees from getting disappointed, and until you maybe decide to give further details so that more experiments can be done - might I suggest the following alternatives:

Post 335851 (Sunlight: "MDA and MDMA from CTH reductive amination", Novel Discourse)
Post 508257 (armageddon: "CTH à la Sunlight - revisited", Methods Discourse)
Post 503533 (Bandil: "Pseudo-"wet"- BH4 amination BH4", Methods Discourse)
Post 461926 (cublium: "NaBH4 is just amazing.", Newbee Forum)
Post 477266 (missing) (Lego: "Reduction of oximes with zinc/ammonium formate", Novel Discourse)
Post 258972 (baalchemist: "Baal,Al/Hg/Nitro, & a 55gal drum.....", Methods Discourse) (now that's a big one  :) )



Greetz A

LaBTop:
what Antoncho/Zealot explained in the first post of this thread!

Look again at Post 302161 (missing) (Antoncho: "Leuckart with 92%+ overall yield", Methods Discourse),
and see that you have to remove ALL refluxed water from the Dean Stark trap, while very gently warming up over 4-6 hours untill it reaches 160-170 C, then you simply close the trap's crane and gently boil it for ~1 h (not 4 hrs, as the original sources say).
""On cooling the rxn crystallizes completely"". If you did not see that, you did something wrong.

""Analysis shows the yield is quantitative at this stage.
The procedure above was originally stated for cyclohexanone, but the author says the identical one was used for P2P, with the results also identical.""

Now here's my explanation what you did wrong, you forgot to READ this CLUE:
""The trap is pre-filled with water.""

You stated a few posts before:
""2. Such that the formed FD is continuously removed from the rxn, or better said tapping off same amount like  FD that distills over - the FD layer gets thicker and thicker, while the amount of water in trap decreases constantly.
 - Now which is the right way to do, Zealot (or Antoncho)? My guess would be the second one, as it seems to allow for a smoother temp. control - and after all, this is the purpose behind it, right? ""

NO, the purpose of the Dean-Stark trap in this special occasion is to fill it FIRST to the TOP with water, so that the amine formyl derivative (FD) can only float on top of the water and will thus flow back in the flask directly, and does not add sufficient cooling mass to the flask to cool the reaction to a too low temperature, which will stop the wanted reaction !!! (This has happened in your cases).

NOW you know what you did wrong, you read again this, and see what you have to do:
Damn slowly remove refluxed water BIT by little BIT from the Dean-Stark trap, keeping the water level in the trap as high as can bee, thus letting all refluxed FD flow slowly back in the refluxing reactionflask :

""So the temp of the reaction is slowly adjusted by gradually removing H2O from the Dean-Stark over 4-6 hours - that leads to a gentle and very even rise of the reaction temperature. When it reaches 160-170 C, you simply close the trap's crane and gently boil it for ~1 h (not 4 hrs, as the original sources say).""

Please try to understand totally what you read, first, before waisting good precursors. LT/

PS: let this special research GO ON!
PS2: This took 2,5 YEARS to find the obvious problem?
You are all dismissed from class, and have to start in grade 1 again. Shame on you.

indole_amine:
I think Armageddon is quite familiar with the use of a Dean-Stark.

He did read the first post, did prefill the trap, and he knew what to do and still got consistently bad yields.

It took him 2.5 minutes to realize that this leuckart variation is bullshit.

Think he won't be taking Leuckart class again...  :P

Please try to understand totally what you read, first - before claiming things like above...


indole_amine

LaBTop:
and everyone else, with this remark:
""My guess would be the second one, as it seems to allow for a smoother temp. control - and after all, this is the purpose behind it, right? ""
While the second one is the one he proposed to do like this :
""2. Such that the formed FD is continuously removed from the rxn, or better said tapping off same amount like FD that distills over - the FD layer gets thicker and thicker, while the amount of water in trap decreases constantly.""
And that is NOT the way it should be done. The FD must flow back in the reaction, nearly exactly as is proposed by him in the first one :
""1. In a way that allows the FD top layer to fall back into rxn flask, i.e. tapping off as much water as is formed, minus the amount of FD that distills too - the FD top layer inside trap stays the same size all the time.
I got a PM where it is explained now, that Armageddon used the prefilled-with-water trap and got zilch (btw the word only Uncle Fester used in this thread) :
""You obviously didn't read Armageddons other posts in this thread: he DID prefill the trap with water, and he DID get the clue that it would have to be tapped off slowly so as to just allow the formyl amphetamine to flow back nto the rxn vessel, while gradually tapping off the water as it is formed...
...over the course of 4-6 hours, until 160°C are reached......followed by 1h boiling at that temp. ......got zilch (40% yield, from P2P)....this Leuckart variation is BULLSHIT!!!!!!!!!!!!""
I did read all Armageddons posts several times in this thread, and have not found any indication there, that he prefilled the trap with water first. This is the only time I am told now, in PM.

So lets presume he did that. Then there are numerous other things which could lead to a low yield.
Zealot described the problems which could arise when you start with an impure ketone (P2P f.ex.):
""The FD is obtained as described earlier for cyclohexanone, w/same nearly quantitative yield. The main factor here is purity: the higher it is, the better yield. If you take an impure ketone, you may get as low as 50% yield; so only a slightly yellow transparent oil should bee used"".
This will mean that if one did not obtain the P2P from a trustable official source which indicates a purity above 98%, then one should double or triple distill ones obviously homebrew P2P, untill sufficient purity is obtained.

And there is much more to read in the first post, which could go wrong if not followed exactly.
A 72% yield with a modified Leuckart with P2P can be obtained, no doubt about that, but I personally have never seen higher yields.

But the proposed addition of a nickel catatalys by Cesium in
Post 303011 (missing) (cesium: "Catalysed Leucard", Methods Discourse)
""The temperature and reaction time during first step could be lowered to approx. 125-135°C and 45 minutes by using 0,5 % of nickel catatalyst prepared by anaerobic thermal decomposition of Ni formate. Yield of N-formyl-MDA is almost quantitative, however due to the harsh acid hydrolysis the overall yield was lowered to 63% after workup. This procedure was originaly published in russian Zh. Obs. Kchim around 1964.""
sounds damn interesting, and if an alkaline hydrolysis as proposed by Zealot would be adopted, it will have the possibility of heightening the yield in the 90+% ranges.
The preparation of such a nickle catalyst is described in :
Post 512060 (missing) (moo: "Nickel catalyzed Leuckart reaction.", Methods Discourse)
""It appears that in
Post 326428 (missing) (zealot: "Äàëüíåéøåå óëó÷øåíèå ðåàêöèè Ëåéêàðòà-zealot’a", Russian HyperLab)
is a procedure for nickel catalyzed Leuckart reaction but the catalyst isn't Raney nickel. The catalyst is prepared by thermal decomposition of nickel formate, using a test tube and a gas flame, and is referred to as pyrophoric nickel. I guess this one from Zealot isn't translated to english yet.
Couln't find anything about using nickel formate in Leuckart, but there is a ref. about Raney nickel.""
in Moo's same post is this Raney nickle one described in the abstract:
""
Abstract
Alk. catalysts in the presence of Raney Ni accelerate the Leuckart reaction and direct the reaction to the formation of predominant formation of secondary amines.  It was shown that the Leuckart reaction goes through the step of dissocn. of HCONH2, and the 1st product is not the amine but its formyl deriv.  Improved techniques for formation of amines are described below. ""

This technique should be concentrated on, to obtain higher yields as 72%.  LT/

PS: this remark of Nicodem should be looked at also:
""Post 529543 (Shane_Warne: "Sodium ethanoate is the same as sodium acetate", Newbee Forum) +
Post 529389 (Nicodem: "Urea hydrolysis and urea pyrolysis", Newbee Forum)
I think most amides get hydrolysed faster with NaOH than HCl, but urea may be an exception, I don't know. You should bee able to notice the end of hydrolysis by the end of CO2 bubbles formation from the boiling stones if you lower the reflux bellow the boiling point for a moment. Usually this is a clear sign in reaction involving CO2 formation (like the Leuckart or decarboxylisations). If I dare making a guess I would say that 6h of reflux would do, but don't forget you need an excess of conc. HCl since it gets neutralised by the forming ammonia (at least a 20% excess). If you will use the 20% HCl put a somewhat larger excess and reflux for a longer time.""
And this one, about never exposing your ketones to extreme pH values:
Post 338541 (lab_bitch: "The chemistry of ketone polymerization", Chemistry Discourse)
""The moral of the story is NEVER, NEVER, NEVER expose ketone to extreme pH, ESPECIALLY if you plan to heat it up (i.e. distillation).  Simple distilled water and sodium bicarb washes are sufficient. ""
And there is a lot more info in that post which should be taken to heart.

This post is also highly interesting:
Post 61613 (psyloxy: "Re: Leukard scaleable ?", Methods Discourse)
""a variation of the Leuckart, that doesn't even use formic acid and has yields reported as high as 70%.""

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