Author Topic: MM reductive/amination using rbf  (Read 514 times)

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alkadelic

  • Guest
MM reductive/amination using rbf
« on: May 07, 2004, 06:53:00 AM »
on methyl/man reductive amination, swim will be using a 2liter round bottom.misskitty advised it wont be an easy stir, but the reflux takes care of most of the reaction. ive read its hard to beggin strring as it is with the foil weighing it down. (Now diffrent procedure, same question), with the MM benzo wacker, could swim get away with the rbf? any suggestion using this round bottom flask... thanks again!

ApprenticeCook

  • Guest
theres not much you can do about the stir...
« Reply #1 on: May 07, 2004, 08:20:00 AM »
theres not much you can do about the stir being hard, its just crap that way... swim had to deal with it so dont fret... but swim uses for this case a smaller stirbar on full speed rather than a bigger one on a lower speed.
Seems to work fine in swims 3L rbf (only using MM amounts tho).

-AC

alkadelic

  • Guest
ACook, i know you talking about a 3liter, but...
« Reply #2 on: May 07, 2004, 10:33:00 AM »
ACook, i know you talking about a 3liter, but if it says to do a medium stir, should swim crank it up to high stir instead with rbf? actually i just found a thread with similar question called rbf v.s. fbf, which i could not find on my previous search. Rhodium states that rbf is good for everything! swim got a 3in/2mm mag bar,is this too long cuz i can file the fucker down if neccesary...help!

abolt

  • Guest
For best results, go slow
« Reply #3 on: May 07, 2004, 11:00:00 AM »
If you are using the "Reynolds wrap" thin foil and the "quick addition" Nitro method for your reaction then what you propose may work. If you are using thicker foil (like the pro's do) or larger reactions then I suggest you use an overhead stirrer. It all depends on the thickness of the foil, and how the Al/sludge breakdown compares to the torque of your stirrer. If you use the Quick addition nitro/Reynolds Wrap/ method, then sufficient agitation may occur, though timing then becomes an important factor.

If you are new to this then I would highly recommend using Al flashing (0.1-0.3 mm thick), utilising an overhead stirrer, slowly adding all your Nitromethane, then slowly dripping in the Ketone.

This method greatly increases your chances of success and good yield. ;)


chilly_willy

  • Guest
use..
« Reply #4 on: May 07, 2004, 11:48:00 AM »
Try using "REYxxxx'x EXTRA heavy duty fxil" squares (25g) compressed with a coffee grinder with your 2L RBF. A standard 5"x7" mag stirrer/hotplate will be fine at first until you figure out what to tweak.  The MM nitro,al/hg is a good starting point.


ApprenticeCook

  • Guest
Re: i can file the fucker down if ...
« Reply #5 on: May 07, 2004, 12:42:00 PM »

i can file the fucker down if neccesary


DONT, if you file it you disrupt the smooth exterior of the bar, and file to far to metal and oh oh.... slowly put it into the rbf and see if it spins with water in there, just make sure it does not bang around with water, if the bar hits al foil in the mix it can spin slightly off its axis and hit the rbf wall a bit harder....

mine does flip around a fair bit in there until most of the al foil is used up but the one i use is 25mm long.

-AC


homeslice

  • Guest
I never had one bit of problem stirring using...
« Reply #6 on: May 07, 2004, 06:51:00 PM »
I never had one bit of problem stirring using a 2L RBF with a 3" egg shaped stirbar. If it takes a second to start, just tip the flask a little to the side and try to stir again. Ya really only have to start/stop the stirring a couple of times. After the addition has begun, it should stir fine on high until finished.


OcoteaCymbarum

  • Guest
Just as long as its egg shaped
« Reply #7 on: May 08, 2004, 03:45:00 AM »
Stirring the MM nitro in a 2L is a real pain if you dont have an egg shaped bar. A one inch rod just wont stir and a 2 inch is just impossible to control. With an egg shaped bar no more problems with Rb flasks. You can find plenty on the net for cheap