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Klute
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Extarct from the Perrin and Armarego book cited above, for DCM:
| Quote: | Dichloromethane [75-09-21 M 84.9, b 40.0°, d 1.325, n 1.42456, n251.4201. Shaken with
portions of conc H2SO4 until the acid layer remained colourless, then washed with water, aqueous 5% Na2C03,
NaHC03 or NaOH, then water again. Pre-dried with CaC12, and distd from CaS04, CaH2 or P2O5. Stored
away from bright light in a brown bottle with Linde type 4A molecular sieves, in an atmosphere of dry N2.
Other purification steps include washing with aq Na2S203, passage through a column of silica gel, and removal
of carbonyl-containing impurities as described under Chloroform. It has also been purified by treatment with
basic alumina, distd, and stored over molecular sieves under nitrogen [Puchot et a]. JACS 108 2353 19861.
Dichloromethane from Japanese sources contained MeOH as stabiliser which is not removed by distn. It can,
however, be removed by standing over activated 3A Molecular Sieves (note that 4A Sieves cause the
development of pressure in bottles), passed through activated A1203 and distd [Gao et al. JACS 109 5771
19871. It has been fractionated through a platinum spinning band column, degassed, and distd onto degassed
molecular sieves (Linde 4A, heated under high vacuum at over 4500 until the pressure readings reached the low
values of mm - -1-2h) [Mohammad and Kosower JACS 93 2713 19711
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\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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Fleaker
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I second Vulture's opinion--DCM and CaH2 probably isn't a good idea. CaH2 is a very, very good base and there are thermodynamic considerations on
forming HCl.
If DCM reacts with P2O5 then it is very, very slow to do so!
I think I also read (again by Armarego in his handy book) that one could even dry DMF with P2O5?! Or perhaps that was somewhere else. I have trouble
believing that.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Panache
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Mood: Instead of being my deliverance, she had a resemblance to a Kat named Frankenstein
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Who's a lucky boy then!!
I wasn't going to reopen this thread after getting these on the weekend, however given it has been, i'm going to gloat.
$20 for both!!!!, sometimes things are perfect, they are as new, even the rubber on the septum is unperished, i also got the reservoir for the top of
the one on the left.
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jarynth
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| Quote: | Originally posted by DNA
I use commercial solvents for LiAlH4 reductions but I do pour in dry 4A molecular sieves. |
Why does everyone apparently use 4A? Is it much cheaper than 3A? As far as I know, it also adsorbs many small molecule solvents such as ethanol.
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Klute
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Beautifull glassware! That looks like one hell of an offer...
BTW, yes I think it's in that book that P2O5 is said to be usitable for drying DMF, removing any traces of Me2NH... I guess that as long as it isn't
hydrated to the acid, it won't cleave the tertiary amide.. They seem to be a very seriosu reference on the subject, I would trust their claims. But
of course most of it is a summary from various litterature, which might not always have been reviewed...
[Edited on 16-10-2008 by Klute]
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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peach
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$20?
That's what John calls a better than stolen price; e.g. the bus fair to the guys house to break in and take it would cost more.
I believe the type of still head Steve has is called a Perkin's.
Here's the QuickFit site with a picture of their's and a description
I think items like these, the still heads, a Markham apparatus and pistol drying tubes fall into the "I'm turning into a glasswhore" catagory, which
is great as far as this whore is concerned.
They're not using the stills at work? I have $20 here that will take them all! And all those nasty health hazard solvents in them. 
Don't know if it's been mentioned, but CurlyArrow has a great section on anhydrous solvents and recycling
The comments are worth reading.
They're all talking about using solvent purification systems, which are essentially a stainless tube packed with alumina, and then maybe Q5 catalyst
in another to deoxygenate the solvent. I've seen photos of these in labs whilst google searching, some labs now have a big bank of them all lined up
with colourful taps to drawn off the solvents, through a spout or septum.
When it comes down it to, they're just metal chromatography columns with no detector and far lower pressures (~10 - 15psi); flash columns under a
blanket of argon. I'd be willing to bet they could be put together at home well below the $30k price tag of the commercial options (albeit, that's for
arrays). With the pressure being that low, perhaps borosillicate tube could be used; e.g. old flash columns. I think the pressure is simply applied by
running some of the inert blanket into the resevoir.
Also working in our favour, when considering a home brew variation, is that we don't have 30 students and members of staff continually pouring solvent
off, everyday. So everything gets smaller. A roll of spooled, thin stainless packed with alumina for each solvent?
These columns are getting ppm's of water very close to distillation from sodium, without the fireballs and explosions.
He also discusses using 3 / 4A molecular sieves for similar work.
I too have seen a number of pages describing CaH as the preferred drying agent for DCM. If anyone has some, shoot me a PM, because my supplier
doesn't, and I could use a bit.
With regards to stolen deals, I just picked up an item that costs $20k to have serviced, new, for two beers. 
[Edited on 25-8-2010 by peach]
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