Author Topic: osmium/brightstar reductive amination question?  (Read 684 times)

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alkadelic

  • Guest
osmium/brightstar reductive amination question?
« on: February 01, 2004, 01:00:00 AM »
I dont have a claisen adapter, so i want to add chemicals all at once, but in the order its said, and plug in my condenser right after adding my ketone/MeAm. or do i need the calisen adapter? Because it does not mention WHEN to add WHAT through the claisen(addition) adapter. so im assuming that after everything is added, i could then plug my condenser and leave running 4.5hrs. will this affect anything? thanx bunch..

Glasya

  • Guest
That is something I would really like to ...
« Reply #1 on: February 01, 2004, 01:08:00 AM »
That is something I would really like to see... you will have one hell of a mess to clean up! You can't add it that fast, the reaction is hot and fast.

alkadelic

  • Guest
i want to know if i really....
« Reply #2 on: February 01, 2004, 01:27:00 AM »
i want to know if i really need the claisen adapter? if u read the procedure youll understand my question better? since it only says to keep adding your chems to the round bottom flask but never says to add your chems through the calisen (addition) adapter at a certain rate or anyting. when is the claisen used in the reaction?

dioulasso

  • Guest
The claisen is used to connect your ...
« Reply #3 on: February 01, 2004, 02:43:00 AM »
The claisen is used to connect your thermometer adapter, to monitor the temp. Of course if you have a 2 neck flask for that, than its not necesseary here. But a claisen ad. has many uses, sould be basic equippement.

Well, solutions may alvais be aded down the condenser...

If working w/ MeNH2 the reaction is not so vigorous.
But if its your first experience with this kind of reaction you should do it carefully ...


Bond_DoubleBond

  • Guest
Re: That is something I would really like to...
« Reply #4 on: February 01, 2004, 03:56:00 AM »

That is something I would really like to see... you will have one hell of a mess to clean up! You can't add it that fast, the reaction is hot and fast.




Swim's done this a bunch of times.  You're probably thinking of Methylman's nitromethane al/hg.


Snakebyte

  • Guest
Don't plug your condenser.
« Reply #5 on: February 03, 2004, 01:46:00 AM »
Don't plug your condenser.  You don't need to monitor the temp...u can monitor how hot the reaction is visually... although if you've never done this reaction it's nice to have a thermometer.  Just add your shit through the top of the condenser a little at a time so u have a nice rolling reflux.  Also if u have another condenser or column add it to the other one so the reaction has more headroom, just in case your reaction gets out of control and everything blasts up the condensor(s).


fanofshulgin

  • Guest
Seeing as this is the newbee forum, i would...
« Reply #6 on: February 03, 2004, 02:57:00 AM »
Seeing as this is the newbee forum, i would wholeheartedly recommend you monitor temperature...if not for anything else but for your own notes.  Having a documented temperature profile written in your labbook will undoubtedly help you on repeat experiments.  A Claisen adaptor is one of the most basic pieces of glassware you will require when wanting to distill.  For one thing, it stops bumping..and allows you to accurately measure the temperature of the material you are collecting...NOT the temperature of the bumped material / vapor.

Fan of Shulgin

EDIT: It DOESNT STOP bumping...it just helps stop the bumped material contaminating your collected distillate.


runne

  • Guest
Addition ideas.
« Reply #7 on: February 03, 2004, 05:19:00 AM »
Before SWIM bought proper equipment, she used to just put the addition funnel on the top of the condensor. I would just MAKE SURE that you have a hose READY to connect to the top of the condenser in case things get out of hand.

When using Nitromethane be aware that you can add LOTS in the beginning only to have it VOLCANO on you when it reaches reflux temperature as the rate of reactions increase.

SWIM tries to add about 15% of the nitro first, then let it come to reflu slowly. THEN when it's at reflux she starts the addition of nitro as fast as it can handle it. She has the flask immerses in water to help moderate the reaction.

She found that greater yields usually happen when the nitro is added first, and the ketone added after. It also ensures that if you have a HUGE error in the first part you still have ALL her precious Ketone. Easy to just setup again and try.

Also be careful that if you don't water cool the flask, you can have methylamine gas starting to form at quite low temperators (30 to 40c reaction temperature). It also doesn't like to condense easily so that is why you need the hose READY to cover the condensor.

Hope this helps.

Just4Fun

  • Guest
Why would you go through the trouble...
« Reply #8 on: February 11, 2004, 12:51:00 AM »
Why would you go through the trouble... just use the MM method :)