04-07-04 11:22
No 499494
Swim has had enough of benzo wackers. They're messy, expensive, the workup is a pain in the ass, benzo sucks (and stains like a motherfucker), and swim's arms are tired from shaking that damned 4L sep funnel near ten times per wacker.
Fuck that.
Swim's next alkene oxidation will be a medium scale buffered performic according to baalchemist.
Post 184264 (baalchemist: "Re: Medium scale performic", Methods Discourse)
One thing concerns swim, however. Now, swim is no modern algebra theorist, but he can calculate volumes given masses and densities. Baal reports that he performed this reaction in a 5L flask. He then proceded to add 750g isosafrole, 2310mls dcm, 718g 35% h2o2, and 1156g 86% formic acid.
The specific gravity of 85% formic acid is 1.2, resulting in about 963mls of aq. acid. The specific gravity of 35% h2o2 is 1.13, resulting in about 635mls of aq. h2o2. The specific gravity of isosafrole is ~1.12, resulting in about 670mls of alkene.
Thats 2310mls dcm + 963mls 86% formic acid + 635mls 35% h2o2 + 670mls alkene = 4578mls of reaction mixture in a 5 liter flask. 5000mls - 4578mls = flask is over 90% full. AND, that is completely discounting the fact that there is 231g sodium bicarbonate dissolved in the mixture. Now, swim understands that there are reactions taking place, and new compounds are being formed and gasses are being evolved. But that shouldn't affect the total reaction mixture volume to such a degree so as to give it proper headroom and a volume possible to stir effectively (which swim imagines would be EXTREMELY necessary since the reaction contents forms two layers).
The ONLY way swim can rationalize this to himself is that a lot of the dcm in this procedure is lost via escaping vapors. If this is the case, can swim still use his uber-efficient 300m reflux coil condenser as he was planning? If dcm boiling away from the reaction system is necessary for ideal reaction conditions, swim is concerned that his condenser will keep too much dcm in the mixture.
Maybe it's nothing more than swim's lack of experience or familiarity with this reaction and he's just making an ass out of himself by spouting off calculations and numbers and units, but swim is beside himself trying to figure out how this reaction worked in a 5L flask.
An explanation would be greatly appreciated.
(Newbee)
04-10-04 01:27
No 499955
I wouldn't worry about it. Remember that the temperature won't go over 40 C because that is the boiling point of DCM. You can get away with very little headroom in the flask. The thing is however is that you want to have a very very good condenser and very cold water to condense and return all the DCM. Swim has use lots of attachments on top of his condenser just to increase the surface area for cooling so that all the DCM is condensed and returned. As far as swim knows you don't want the DCM to disappear, this is what a reflux is for, to capture and cool the vapour and RETURN it to the reaction flask.
Just add the reactants very slowly (dropwise) and you should be fine. All in all it is a much nicer ketone preparation method than others.
(Chef d'Equippe)
04-10-04 12:37
No 500037
Youre stirring bi-phasic liquids, not pudding. This is not an Al/Hg/nitro reaction reaction either where massive headroom is needed. Do you think I sit around making this shit up? If you don't understand or comprehend, then don't attempt. Its that simple. My proven methods & techniques don't require the scrutiny of an ignorant wannabee. Class dismissed.......................
GODISNOWHERE
"Sadistic Surgeon of the Mind, Sadist of the Noblest Blood"
-Slayer-