The Vespiary

The Hive => Newbee Forum => Topic started by: grandpa on June 03, 2004, 01:10:00 PM

Title: Flat bottom flask for al/hg reductive amination ?
Post by: grandpa on June 03, 2004, 01:10:00 PM

Methyl Man writeup for Reductive amination of "MDP2P with Al/Hg + nitromethane" calls for a 2 liter FLAT bottom flask.

ref.:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/alhg-meno2.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/alhg-meno2.html)

SWIM is wondering why a Flat bottom flask is needed and what is against using a round bottom flask of the same size ???

Title: Stirring?
Post by: Novice on June 03, 2004, 01:30:00 PM

Probably because magnetic stirring is easier in a flat bottomed flask, but if you ask me it doesn't make a big difference as the stir bar doesn't stir whether you're using a FBF or a RBF... :-P

Title: very true
Post by: psytech on June 03, 2004, 04:05:00 PM

true dat

Title: yeah, damn al/hg chunkies stopping the stirbar
Post by: ApprenticeCook on June 03, 2004, 10:09:00 PM

yeah, damn al/hg chunkies stopping the stirbar suck ass... fbf/rbf whatevers on hand... no reason chemically but yeah in the ease of mag stir in al/hg fbf is a tiny bit easier.

Swim uses a glass rod through the other rbf port to "jump start" the bar into stirring, seems to do the trick.

Title: overhead stirrers
Post by: jackhole on June 04, 2004, 12:09:00 PM

You know, you can use overhead stirrers in an Erlenmeyer flask and just direct the flow of hydrogen gas out of the nipple with tubing. That is, if you're interested in achieving the highest possible yields - 95% and above.

Title: 95% !?
Post by: hypo on June 04, 2004, 12:15:00 PM

how do yo avoid formation of higher amines and other condensation products?
or do you count them to your yield?
(or do you not know how to compute yield?)

ps: most of methyl_man's comments can safely be ignored. someone really should
make a new state-of-the-art writeup.

Title: what do you mean by "most of methyl_man's
Post by: grandpa on June 04, 2004, 02:14:00 PM

what do you mean by "most of methyl_man's comments can safely be ignored". I tought that this writeup was state-of-the-art ?

Do you have any ways to improve it ?

Title: yield
Post by: jackhole on June 04, 2004, 03:00:00 PM

Yes, I know how to compute (calculate) my yield. I have performed alkylations of P2P and MDP2P and received in excess of 95% mole-to-mole yield after gassing, on more than one occasion. Of course, I was using my method, which involved that overhead stirrer so all of the aluminum was exposed to the Schiff base. No wonder so many of you guys end up with shitty yields. If you would start off with PURE precursors and perform the reaction CORRECTLY - and that means by ensuring that the ENTIRE surface of the aluminum comes into contact with the Schiff base, maybe you would receive a 95%+ yield too.

Title: sharp critizism against the MM writeup
Post by: Rhodium on June 04, 2004, 03:17:00 PM

This thread includes sharp critizism against the MM writeup:

Post 319058 (https://www.thevespiary.org/talk/index.php?topic=9131.msg31905800#msg31905800)

(Rhodium: "Distill or Recrystallize!", Methods Discourse)