Author Topic: acetadehydemethylamine soluble in toluene?  (Read 1557 times)

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El_Zorro

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acetadehydemethylamine soluble in toluene?
« on: July 23, 2003, 11:25:00 PM »
How soluble in toluene or xylene would acetaldehydemethylimine?  What would be a good procedure for getting it in there?  Does MeAm*HCl form the imine very well, or does the freebase have to be used?  If the freebase has to be used, then would a good procedure be just to put some acetaldehyde, toluene, and MeAm*HCl in a flask, and add a solution of NaOH, and stir?

Edit:  Ok, so I found out that acetaldehyde is miscible with water as well as most NP solvents.  So I guess the methylimine of acetaldehyde would be soluble in toluene.  So my only real question now is whether or not MeAm*HCl would form the imine with acetaldehyde or not.  Wouldn't it be a lot harder for the HCl salt of MeAm to form the imine than the freebase, since the amine group is already protonated?  So would it still form the imine, or would one have to use freebase MeAm?


Rhodium

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You are tackling a sensitive reaction here...
« Reply #1 on: July 26, 2003, 06:39:00 PM »
I would expect the imine to be very soluble in toluene. Also, I definitely think the reaction needs to ge performed anhydrously to work at all (remove the water as fast as it is formed in the condensation between amine and aldehyde with molecular sieves). Short-chain imines like this are known to easily polymerize, so you should keep the temperature down as well, around 0°C is probably enough.

El_Zorro

  • Guest
Yeah, I see what you're saying, Rhod.
« Reply #2 on: July 26, 2003, 06:54:00 PM »
Yeah, I see what you're saying, Rhod.  My idea was to dissolve some acetaldehyde in toluene, add the MeAm*HCl, chill it down to 0°C, then basify the solution with some aqueous NaOH, which has also been chilled to 0°C.  Then stir the mix for a minute or two, and draw off the water layer, and add a drying agent, and let it sit in the freezer for a little bit.  I guess if the NaOH solution was conc., then it would make all of the acetaldehyde and MeAm harder to keep dissolved in the aqueous layer, which would help to get them into the toluene layer to react.

I guess one could just bubble MeAm gas into the toluene, but how soluble in toluene would MeAm be?


Rhodium

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Never mix NaOH with acetaldehyde - instant...
« Reply #3 on: July 26, 2003, 08:13:00 PM »
Never mix NaOH with acetaldehyde - instant side-reactions.

Anhydrous MeNH2 is soluble in toluene to an extent of about 10% if I remember correctly.

El_Zorro

  • Guest
Damn, I guess that means that NaOH couldn't be
« Reply #4 on: July 26, 2003, 08:36:00 PM »
Damn, I guess that means that NaOH couldn't be used as a drying agent if someone was trying to distill acetaldehyde. :(   Ok, so my next question is, would MeAm*HCl form the imine?  I wouldn't think so, since the imine group is protonated, but I don't really know.  In

https://www.thevespiary.org/rhodium/Rhodium/chemistry/grignardimine.html

the guy says that he used MeAm*HCl and got an 86% molar yeild.  Is he full of shit?


Rhodium

  • Guest
grignard on acetaldehyde methylimine -> meth
« Reply #5 on: July 26, 2003, 08:56:00 PM »
I think that the guy has exaggerated his success somewhat, especially as you look at Vera Evdokimoff's original article which gave only 40% yield using MeNH2 freebase and Na2SO4 as drying agent. But now in the age of molecular sieves that yield should easily be exceeded. 

Read up on the posts linked from

Post 248673

(Rhodium: "Re: Novel BzCl To Meth In One Pot", Chemistry Discourse)

El_Zorro

  • Guest
Yeah, it's a great age we live in, where ...
« Reply #6 on: July 26, 2003, 11:55:00 PM »
Yeah, it's a great age we live in, where things like molecular seives exist, but are restricted from hands like mine.

But my question still stands, will the HCl salt of methylamine still form the imine?


Rhodium

  • Guest
dessiccants & salt
« Reply #7 on: July 27, 2003, 12:48:00 AM »
I would not believe that molecular sieves are restricted, as they have a lot of non-chemistry applications too as dessicants. It is just a matter of looking for them. You can use silica gel also, which is found in those "do not eat" drying bags commonly shipped with hard drives etc.

Anyway, the salt will not form the imine as good as the freebase will. Also, the HCl part of the salt will react with your grignard reagent later...

El_Zorro

  • Guest
Yeah, I thought about the HCl reacting with...
« Reply #8 on: July 27, 2003, 07:01:00 PM »
Yeah, I thought about the HCl reacting with the Grignard after I made that post.

But dammit, I don't wanna have to gas toluene with MeAm gas.  grumble grumble....