chemrox
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heterocycles and red goo
I've been working on heterocyclic compounds these last few months. A common purification step in these is distillation at low pressure. Why?
Becaue a lot of side reactions are involved that make deeply colored gooey compounds one has to distill or use chromatography to get rid of (so to
speak). So why is thisthe case? Am I right in saying this is a characteristic of heterocycles (although common with other kinds of arylamines) ?
So are these like PAH's and phenolic dyes we're making on the side?
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Nicodem
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Side reactions are not characteristic just for heterocyclic chemistry but for most chemistry.
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Sauron
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Absolutely. That's what short path stills, kugelrohrs etc are for. And as you say sometimes chromatography is the only way out. We used to call goop
like that "mung" (rhymes with hung). The dreaded mung. The Mung That Ate Chicago. It Came From Out of Mung. and other B-movie scifi titles.
Tars, polymers, high MW stuff. Sometimes can be very frustrating.
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garage chemist
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As one does organic chemistry, one will find out lots of methods to make goop or tar out of expensive fine chemicals.
I already know how to make tar using a grignard...
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I am a fish
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| Quote: | Originally posted by chemrox
A common purification step in these is distillation at low pressure. Why? |
Presumably to lower the boiling point of your desired product. If you require simple distillation (i.e. straightforward separation of your mixture,
without any reactions going on within it) then you will want to avoid high temperatures.
| Quote: | Originally posted by Sauron
Tars, polymers, high MW stuff. Sometimes can be very frustrating.
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They can also be serendipitous:
http://en.wikipedia.org/wiki/Aniline_purple
[Edited on 2-5-2007 by I am a fish]
1f `/0u (4|\\| |234d 7|-|15, `/0u |234||`/ |\\|33d 70 937 0u7 /\\/\\0|23.
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chemrox
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Kuglerohr will be the way to go. I can't maintain high vac with enough bubbles to avoid bumping and the holdup on my column is too much for the
amount I'm distilling. The Snyder is a lot of fun by the way... sounds like a windchime tied to a happy dog's tail. Absent a Kuglerohor maybe a
short vigeraux and a cold finger will be the way to collect it all.
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chemrox
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| Quote: | | I already know how to make tar using a grignard... |
I've made a lot of Grignards .. what's going on?
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chemrox
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red goo still chaser
I should have thought of this sooner. I need a chaser in my still pot. If my compound distills at 125/1mm could I use pump oil as a chaser? What
else comes to mind? Everything else I have boils lower or could react or both.
[Merged from new thread]
[Edited on 3-5-2007 by I am a fish]
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Nicodem
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| Quote: | Originally posted by chemrox
I should have thought of this sooner. I need a chaser in my still pot. If my compound distills at 125/1mm could I use pump oil as a chaser? What
else comes to mind? Everything else I have boils lower or could react or both. |
Why another thread on the same topic?
http://sciencemadness.org/talk/viewthread.php?tid=8413
Edit: ...and http://sciencemadness.org/talk/viewthread.php?tid=8392
[Edited on by Nicodem]
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I am a fish
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Do not create new threads on exactly the same topic. If you feel as if your original thread isn't getting enough attention, then tough luck.
1f `/0u (4|\\| |234d 7|-|15, `/0u |234||`/ |\\|33d 70 937 0u7 /\\/\\0|23.
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chemrox
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shit I'm sorry I've done this too much
taking a break for awhile
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