"what's up with the balloon?"
I didn't think much of this setup until several labmates asked me the question that became the title of this post. As you can see, there's a balloon in the hood.
The first question for you, readers, is why? (Just so I don't have to answer it again.) The second question is...what's in there? It's been awhile since we posted a mystery reaction. Have fun guessing!
(This should be pretty easy.)
10 comments:
I see that you don't double. We use baloon-in-baloon so that way if one baloon ruptures the reaction is not lost (and hood not burned, in case of hydrogenations).
Also, I suppose you are doing hydrogenation because of the color and because your not-so-inflated baloon stil stands upright. But I would not use septa/needle in this case because hydrogen has extremely low viscosity and leaks easily through the septa. (The 3-way stopcock with bottom joint for vacuum/gas purge is a much better system for hydrogenating under baloon.)
I didn't know that. Thanks!
What's in there? 95% of the tar products from Stanley Miller's experiment.
If you are using a needle and septa, use a longer needle so that the hydrogen bubbles through the solution. That's been the bane of my existence over the past few days.
I've never had a balloon blow up in the hood, always when I'm filling them up with the gas. But, I use the double-balloon technique, too, usually with two very different colored balloons so I can get all sorts of neat color combinations.
What i found works well is using larger flask (>5-10 fold of the react mixture volume) - that way you have enough headspace for vac purge and enough hydrogen in contact with liquid surface. With Ar flush followed by 3x vac/H2 purge (use EtOH or EtOAc as a solvent) there is no need to bubble through the solution.
The answer to "the Great Question of Life, The Universe, and Everything" is...
Hydrogen!
Quite a few UKian institutions require triple ballooning!
stirring the living bejesus out of the reaction helps too
Rest assured that the living bejesus was stirred out of it. ;)
Thanks to everyone for throwing out suggestions. I've only been with this synthesis thing for about six months, so it's good to hear from people who know what they're doing.
I normally don't bubble hydrogen through the solution, but this last, large(r) scale reaction I've been running (~20 g), I've found that bubbling through the solution works better than having that thick blanket of hydrogen over top of the reaction itself. But, that could just be this reaction and probably isn't a general rule.
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