09-05-03 15:48
No 457386
I feel like trying something and I would appreciate any inputs on the subject. Round Bottom wrote a great post using methylamine hydrochloride lately.
So I'm thinking about modifying it a bit by preforming the imine before reducing it with the aluminium amalgam.
Here is my plan:
-Place 70 grams MeAM HCl in a Rb flask sitting in an salt water/ice bath.
-Add MeOH cooled at -20.
-Drip in 35% NaOH(at -20)slowly to keep as cold as possible, just enough to liberate the 70 grams.
- Add the ketone
- Bring the pH down to 4.5 with dilute HCl.
- Leave to stir, stoppered.
Now, there are still a lot i need to verify and decide.
I dont know if methylamine HCl is soluble in MeOH, I have yet to find out. In case its not really soluble, and since MeAm is soluble in MeOH, would the 35% NaOH sln still liberate the MeAm and put it in solution?(i dont see why not)
The ketone is miscible with MeOH. It should be a good solvent. The question is how long should I leave under stirring for the imine formation?
Also, if MeAm HCl is soluble in MeOH, then would a stronger base solution be better to cut down on the water?
Then add this to an aluminium amalgam. In one shot, as it shouldnt be more exothermic then RB's write-up.
And finish off with the usual work-up
This procedure should produce less smell and increase yields even more, if proven to work.
Anybody have any thoughts are experience with something similar?
Thanks
(Hive Bee)
09-05-03 16:52
No 457396
I'm really beginning to think that this makes a big difference in yield. The highest yeild was obtained when 40% meam was allowed to sit with the ketone for 3 hours prior to addition. Meam always gave better yields than MeNO2. I'm guessing because of having meam readily available to for the imine. You will notice the ketone warm up and change color over an hour after addition of 40% meam to it. It's also been observed that with this reaction less is more. Using very little meam and aluminum seemed to produce better yields (1: 1.3 ketone/meam. If I remember correctly, the salt was not very soluable in MeOH.
(Hive Bee)
09-06-03 06:13
No 457458
I guess I'll have to find out all by myself and report after, I'll let u guys know what happened
(Old P2P Cook)
09-06-03 11:23
No 457486
Is it that much trouble to prepare 10% methylammine freebase in methanol via absorption of gaseous methylamine freebase? I always thought that this was a rather simple procedure and sort of fun. It really doesn't seem much more time consuming that the plan you detailed wherein the methylamine freebase is generated in situ.
I can't say that the generation of the methylamine freebase in situ is a bad idea since I never tried it but using pure methylamine freebase in methanol rather than the in situ generation just seems so much cleaner.
All those moments will be lost in time, like tears in rain.
(Hive Bee)
09-06-03 19:57
No 457539
I guess Terbium I will do that next time, with boro.
Anyway, I did as planned this afternoon, when I added the solution to the amalgam, the temp slowly rose to around 65 degrees. I let it go for about 4 hours before basifying it.
When I extracted with xylene, instead of the usual cloudy np, it was yellow. So I washed 3 times with 5%NaOH. Then extracted in 10% HCl. The water layer turned a rust-orange and the xylene pink!
When I washed with some fresh np, it also turned pink! After basification and extraction, the np is still orangy.
Something else seems to be follwing my freebase. I cant see what it is. Usually the xylene is crystal clear when after the extraction. Any ideas?