10-11-03 01:47
No 463880
Can anyone provide the equation (or info on the reaction) for the above?
thanks - peace out
(Hive Bee)
10-11-03 03:15
No 463890
it should help you
http://www.orgsyn.org/orgsyn/prep.asp?pr
(Hive Bee)
10-11-03 22:20
No 464058
I looked over the synth you posted in your reply. Problem with pretty much all MeAm synth write-ups that I've read is that I've yet to find one that's anything more then generalized. So I decided to write my own
This is gonna be a procedural, step-by-step write up, along with observations. I'm hoping to compile it from about half a dozen documents on the subject. Once's SWIM's done (and perfected) a solid MeAm synth, the writeup would be posted for edits, insights, and the like.
I started by looking for a balanced reaction (equation) and came up with:
2CH2O + NH4Cl -----> CH3NH2 * HCL + HCO2H
In terms of mass of the reagents & desired products, I came up with (roughly):
162.32g of 37% CHO2 Soln (2 moles / CH2O) + 53.49g/mol NH4Cl (1 mole) ----> [yields] (1 mole) 67.51g/CH3NH2 * HCl
Hence my first question: Why to most of these writeups call for a great excess of reagents?
I decided that SWIM's trial run would be exactly as the equation states, to (theoretically) yield 1 mole final product. I'd like to run through the rxn procedure very briefly so that fuckups could perhaps be prevented.
Steps:
1. Combine reagents in said quantities, in say a 1L Round-bottom flask in a vacuum distillation setup (with vacuum hose NOT attached). Rxn flask is set in an oil bath. Commence (light-to-medium) stirring.
2. Rxn flask is heated to 104C to distill whatever water/solvents are present, and maintained at this temperature until nothing more comes over (roughly 4-6 hours).
3. Rxn flask is then allowed to cool to room temperature, at which point Ammonium Chloride crystals will start to separate out of the mixture.
4. The Ammonium Chloride crystals are vaccum filtered out of the rxn flask and the rxn contents are returned to the oil bath for distillation, this time under vacuum, until MeAm crystals start to come out of solution.
5. The contents of the rxn flask are once again filtered, this time to retrieve the MeAm crystals, and then the rxn flask is returned to the oil bath and heated for about an hour. Afterwards, the rxn flask is again allowed to cool to room temp, and a second batch of MeAm crystals is retrieved from the rxn solution.
6. The 2 batches of MeAm crystals are combined in a beaker, and washed with Chloroform. (about half a liter of chloroform is dumped into the beaker, mixed, and then the beaker's contents are vacuum filtered to retrieve clean MeAm.HCl)
---------------------- END ----------------------------
I know for sure that I'm probably off by a mile because much of the stuff I've read about MeAm synth doesn't seem to work this way. I'd appreciate any help/corrections/pointers, which I'm happy to share in the future photo-essay writeup :)
One last thing: On the issue of fumes, unfortunately SWIM doesn't have the ability to lead a hose out from the vacuum nipple and outside the house. So I'm wondering if working in a mildly ventilated area (and considering the quantities involved in the proposed rxn) would be hazardous in any way? Also, is it possible to neutralize the fumes? say by bubbling them through a beaker with sat NaOH soln or something?
Can't wait to hear back, SWIM's itching to run this baby through the glassware.
Peace out -
Houston..................?????
(Hive Bee)
10-12-03 02:08
No 464086
Its good to see such invested interest. You must've missed the MeAm FAQ at ../rhodium /methyla
You want an excess of the ammonium chloride to prevent the methylamine that is formed from going one step further to form dimethylamine.
Regarding your procedure outline, you will probably need to filter ammonium chloride twice. The idea is that the MeAm will have trouble crystallizing if there are nh4cl crystals present. However, all of the nh4cl is not likely to precipitate the first time unless it is very concentrated, but you dont want to concentrate it so much that your MeAm co-precipitates along with the Am.Hcl. Vogel's procedure (in the post above) which reduces to half the volume after the initial cooling and filtering is a good guideline. Once all the nh4cl is precipitated and removed some MeAm.hcl will crystallize on standing if it is concentrated enough.
An additional tip is that a good way to recognize whether the salt is nh4cl or MeAm.hcl is that MeAm.hcl will feel slimy and dissolve if a small amount is rubbed between the fingers, because of its hygroscopic nature, while the nh4cl will feel gritty and not dissolve.