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Author: Subject: The short questions thread (3)
Vargouille
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[*] posted on 7-1-2013 at 12:50


I believe that it is due to the release of gases trapped in the filtrate. The movement of the liquid is part of what releases the trapped gases, akin to how shaking a soda bottle results in foaming. While mentioning soda, recall that putting mentos in soda releases the gases because they provide nucleation sites. The filter paper or frit on your funnel will do the same thing, to a greater or lesser extent, and the application of vacuum aids the movement of the gases out of the filtrate. These gases carry some of the liquid along for a short while, making the foam.
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Hexavalent
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[*] posted on 7-1-2013 at 14:02


Why foam, though, as opposed to simply bubbling out?



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learningChem
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[*] posted on 7-1-2013 at 14:19


I tried the canizzaro reaction on ~23 grams of formalin (allegedly 40%) - I distilled ~3.6g methanol out of it and got a sludge of crystals which I'm not yet sure how to work up. I guess it can be done but yields are not going to be too good...

I'm not sure if I can buy formic acid here - I thought the local nazis had banned it for peasants like me, but now I'm not sure - I'll have to check again.
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Vargouille
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[*] posted on 7-1-2013 at 14:45


The lack of formation of large bubbles is likely jointly caused by a low amount of atmospheric gases trapped in common filtrates (as opposed to carbonated beverages) and the relatively rapidity of nucleation. The speed of most filtrations means that smaller bubbles don't have the time to coalesce into larger ones.
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[*] posted on 8-1-2013 at 00:05


Does anyone know where to find the melting point for 2,4-dimethoxyphenethylamine hydrochloride? I can't seem to find it anywhere. I have looked in the printed version of Beilstein, Combined chemical dictionary and The shulgin index, and searched google. I have found some articles where they make 2,4-dimethoxyphenethylamine, but none of them isolate it as the hydrochloride.

The only thing I can seem to find is the melting point of the picrate, the hydrogenoxalate and the boiling point for the freebase.

[Edited on 8-1-2013 by Bronstein]
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[*] posted on 8-1-2013 at 13:25


Quote: Originally posted by Bronstein  
Does anyone know where to find the melting point for 2,4-dimethoxyphenethylamine hydrochloride?

Beilstein gives these two references for the mp of the hydrochloride:

mp 149-150 °C, Bailey et al., Journal - Association of Official Analytical Chemists 1974, 57, 70.

mp 159 °C, Kappe, Armstrong, Journal of Medicinal Chemistry 1965, 8, 368-372.




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learningChem
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[*] posted on 9-1-2013 at 13:03


How does MnO2 oxidize toluene to benzaldehyde? Do the O atoms from the Mn oxide go to the toluene or is the oxide a catalyst of sorts?
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[*] posted on 9-1-2013 at 19:06


New Question:
Is it possible to ball-mill silicon powder (starting with, say 100mµ)? I mean this stuff is quite hard (6,5 vs. 2,75 for Al) and I have no clue on the grindability in a (steel vessel) ballmill.
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Hexavalent
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[*] posted on 10-1-2013 at 08:36


Quote: Originally posted by learningChem  
How does MnO2 oxidize toluene to benzaldehyde? Do the O atoms from the Mn oxide go to the toluene or is the oxide a catalyst of sorts?


The oxidation of toluene is usually done using KMnO4, which could produce benzaldehyde in theory, but would be exceptionally difficult to control: for this reason, this concept usually produces benzoic acid and manganese dioxide.

Perhaps this is what you mean?

[Edited on 10-1-2013 by Hexavalent]




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[*] posted on 10-1-2013 at 12:01


Hexavalent,

Toluene can be converted into benzaldehyde using MnO2. See for instance

http://www.google.com/patents/US613460

Reaction of toluene and MnO2 in ~60% sulphuric acid --> benzaldehyde. My question is : where does the O come from - what happens to the MnO2?

-------

I'll put this in the benzaldehyde sticky thread too...

[Edited on 10-1-2013 by learningChem]
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[*] posted on 10-1-2013 at 15:12


MnO2 (Mn IV) + 4H+ + 2e- ---> Mn2+ + 2H2O
Manganese dioxide is converted into manganese II sulfate.
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[*] posted on 10-1-2013 at 16:32


Ahh - thanks barley81

What about the 'common' equation? Something like this?

MnO2 + H2SO4 + Ph-CH3 --> MnSO4 + Ph-CHO + H2O + H2
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[*] posted on 10-1-2013 at 16:42


Oh, here I was thinking you were looking for the reaction mechanism.

The balanced ionic equation, unless I've made an egregious error, is:

2MnO2 + 4H+ + PhCH3 -> PhCHO + 2Mn+2 + 3H2O

[Edited on 11-1-2013 by Vargouille]
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[*] posted on 10-1-2013 at 16:55


2MnO2 + 2H2SO4 + PhCH3 --> PhCHO + 2MnSO4 + 3H2O

?
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[*] posted on 11-1-2013 at 02:57


Yup. Only difference is that the sulfate is ignored because it doesn't take part in the reaction.
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[*] posted on 13-1-2013 at 10:36


Was wondering if anyone here know where or how I might be able to do a "bulk" search of CAS numbers?

I have a long list of CAS numbers that I need the names for, and I would like to just feed them into a database search and get a text file out or similar.

I know ChemACX can do it but haven't been able to access their site today..




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[*] posted on 14-1-2013 at 21:44


Quote: Originally posted by bahamuth  
Was wondering if anyone here know where or how I might be able to do a "bulk" search of CAS numbers?

I have a long list of CAS numbers that I need the names for, and I would like to just feed them into a database search and get a text file out or similar.

I know ChemACX can do it but haven't been able to access their site today..


Is this for that ebay auction? I just cut-n-pasted them all from a spreadsheet into the sigma aldrich website! Its quite picked over already :(




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bahamuth
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[*] posted on 15-1-2013 at 13:04


Quote: Originally posted by mr.crow  
Quote: Originally posted by bahamuth  
Was wondering if anyone here know where or how I might be able to do a "bulk" search of CAS numbers?

I have a long list of CAS numbers that I need the names for, and I would like to just feed them into a database search and get a text file out or similar.

I know ChemACX can do it but haven't been able to access their site today..


Is this for that ebay auction? I just cut-n-pasted them all from a spreadsheet into the sigma aldrich website! Its quite picked over already :(


Got me there. But I am looking for unusual stuff, molecular biology stuff in unopened containers. Mostly buffer reagents and the like.

Saw that auction a very long time ago but only recently got my hands on some money to procure some of the stuff I need.

Anyways, did a bulk search with a trial ChemACX and opened the resulting exported file in ChemBioFinder Ultra to browse both the names and the structures.

Btw, how did you manage to bulk interrogate all those CAS numbers at Sigma A, or did you input one and one.....?




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[*] posted on 16-1-2013 at 08:15


Just Ctrl-C, Ctrl-V! I tired to write a scraper program in Python but it needs cookies or something to work.



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[*] posted on 22-1-2013 at 05:06


How do I gain access to the reference section forum?
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[*] posted on 22-1-2013 at 05:30


Quote: Originally posted by kingkey24  
How do I gain access to the reference section forum?


Send a U2U message to Polverone requesting access.
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Hexavalent
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[*] posted on 30-1-2013 at 09:13
Units for hygroscopy?


Is there a unit for measuring/quantifying the hygroscopy of a compound? Perhaps something like moles(water)/minute?

[Edited on 30-1-2013 by Hexavalent]




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[*] posted on 30-1-2013 at 13:55


Apparently there is a source (Lang's Handbook of Chemistry) that states the hygroscopy of certain compounds in terms of grams water per gram of material. There is also the concept of a "critical relative humidity", which describes the relative humidity below which a compound will not absorb water from the air.
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[*] posted on 30-1-2013 at 14:33


Should copper powder react with fluorescein?



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[*] posted on 30-1-2013 at 15:10


I can't imagine that it would, at least, not on a reasonable timeline. Copper isn't likely to even bat an eye at the ketone, ether, or alcohol moieties, and the carboxyl group isn't likely to do much except in the presence of atmospheric oxygen. Even then, fluorescein's pKa is only 6.4, so the reaction would be quite slow.
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