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Author: Subject: The short questions thread (2)
chemoleo
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[*] posted on 8-7-2009 at 17:34


Would 1,3,5 tribromo (iodo?) benzene be reactive towards thiols, -SH, forming Phe(S-R)3?
I doubt it, as it is on the ring - but confirmation would be appreciated.
PS alkane-Br + HS-R readily reacts to form alkane-S-R and HBr.

Also, cyanogen bromide (Br-CN) forms (when polymerised with acids), cyanuric bromide, which is the triply substituted triazin ring (-C(Br)=N-)3

Would it be possible to condense/polymerise bromo or chloroacetonitrile, Cl-CH2-CN to the bromo/chloro-methyl 1, 3, 5 triazin compound?
The structure would be the same as shown above, except with a methylene (CH2) group between the Cl/Br and ring carbon.

Thoughts?




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[*] posted on 8-7-2009 at 19:47


Is a vacuum capable of pulling 21" of Hg good or acceptable for such tasks as vacuum filtration and vacuum distillation or is that too weak?



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Formula409
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[*] posted on 9-7-2009 at 23:31


Could someone find the solubility of Thiourea Dioxide and d-Camphor in Isopropanol and Toluene pretty please? I'm having no luck.

Formula409.

[Edited on 10-7-2009 by Formula409]
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[*] posted on 10-7-2009 at 00:43


Quote: Originally posted by chemoleo  
Would 1,3,5 tribromo (iodo?) benzene be reactive towards thiols, -SH, forming Phe(S-R)3?

No, it can not react with thiols or thioxides unless transition metal catalysed or under extreme conditions.
Quote:
PS alkane-Br + HS-R readily reacts to form alkane-S-R and HBr.

Yes, most primary alkyl bromides will alkylate thiols, even under neutral or only slightly acidic conditions and even at room temperature. The reaction rate will depend on the pH, solvent medium and alkyl bromide's electrophilicity. Secondary alkyl bromides are much less reactive and tertiary alkyl bromides mostly succumb to other side reactions since they are unable to undergo SN2 reaction pathways.
Quote:
Also, cyanogen bromide (Br-CN) forms (when polymerised with acids), cyanuric bromide, which is the triply substituted triazin ring (-C(Br)=N-)3

Would it be possible to condense/polymerise bromo or chloroacetonitrile, Cl-CH2-CN to the bromo/chloro-methyl 1, 3, 5 triazin compound?
The structure would be the same as shown above, except with a methylene (CH2) group between the Cl/Br and ring carbon.

Cyanuric bromide and chloride are both already quite electrophilic, even much more so than the coresponding 2,4,6-tris(halomethyl)-s-triazine would be (which due to the electronic effects should be less reactive than benzyl halides).
All nitriles, in principle, can be trimerized, but in practice this is anything but easy (except for cyanogen halides and such). For this reason, other routes are generally used to prepare s-triazines. For example, 2,4,6-tris(chloromethyl)-s-triazine was prepared from the coresponding alkyl imidate (Journal of Organic Chemistry, 26 (1961) 2778-2784).
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querjek
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[*] posted on 10-7-2009 at 05:37


Quote: Originally posted by crazyboy  
Is a vacuum capable of pulling 21" of Hg good or acceptable for such tasks as vacuum filtration and vacuum distillation or is that too weak?

It's definitely enough for vacuum filtration.

As for vacuum distillation, 21" corresponds to ~530mmHg. This will lower the boiling point of compounds by roughly 50deg.C. It all depends on whether or not this is enough for whatever you're looking to distill.

[Edited on 10-7-2009 by querjek]




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[*] posted on 11-7-2009 at 11:32


On the suggestion of an old thread, I'm considering using two in-line bilge blower fans for a fume hood. Can anyone give me an idea of what kind of power these have? Am I wasting my time? I was planning on using an absorber column, so there will be some resistance to airflow, but not a lot, hopefully.



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querjek
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[*] posted on 11-7-2009 at 18:56


Does anybody know where/if I can find phase diagrams of organic compounds?



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JohnWW
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[*] posted on 11-7-2009 at 19:21


Quote: Originally posted by querjek  
Does anybody know where/if I can find phase diagrams of organic compounds?
There are phase diagrams of many binary and some ternary mixtures of organic compounds in the International Critical Tables (1930), which can be downloaded as a 310 Mb PDF file. Some such phase diagrams are also give in Chapter 3 of Perry's Chemical Engineers' Handbook, 7th Edition 1997 and 8th Edition 2008; and in the CRC Handbook Of Chemistry & Physics, of which the 87th, 88th, and (the latest) 89th Editions can be downloaded. Links for downloading these are in appropriate threads in the References section.
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querjek
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[*] posted on 12-7-2009 at 09:06


Thank you very much!

Another question:

I've got some spare Anise oil laying around and want to try to refine it a bit.

The composition is said to be mostly:
Phellandrene - b.p. ~172deg.C
terpineol - b.p. ~219deg.C
anethole - b.p. ~234deg.C

If I were to place 20mL of this in an open 100mL beaker and slowly raise the temperature to 175deg.C, do I run the risk of losing the terpiniol and anethole to the atmosphere?

I know that a full-fledged fractional distillation would be my best bet, but if this would work, I would feel more comfortable not constantly watching the setup for any temperature spikes.




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[*] posted on 12-7-2009 at 09:48


Raising the temperature of anise oil to just above the boiling point of phellandrene, which is substantially the most volatile major component, would result in steady loss of that component, as at 172ºC its vapor pressure equals normal atmospheric pressure. There would also be a much slower loss of the less volatile components at that temperature, having much lesser vapor pressures. To separate and retain these components, as relatively pure fractions according to their normal boiling points, would require fractional distillation. Preparative-scale gas-liquid chromatography would produce purer fractions, although still likely to be contaminated with minor components having very similar molecular weights and boiling points to those of the major components.
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[*] posted on 12-7-2009 at 10:21


I'm trying to find procedures for acetylation of aniline with dilute acetic acid. Two references I have are for Matheson and Co. Eng. Pat. 6220 and Deutsches Reichspatent 98070. How do I access these patents?

[Edited on 12-7-2009 by manimal]
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Formatik
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[*] posted on 12-7-2009 at 10:31


Use the european patent office (espacenet) to find your GB and DE patents. Also, because that British patent is way old, enter the full year before the patent number. Under "number search" enter your country codes before desired patents, e.g. DE98070.

[Edited on 12-7-2009 by Formatik]
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[*] posted on 12-7-2009 at 11:09
COBALT NITRATE


Is cobalt nitrate supposed to be purple ?
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manimal
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[*] posted on 12-7-2009 at 11:24


I tried "DE98070", but my search was unsuccessful. I'm thinking that there is a special format for entering old patents. Unfortunately, I dont know the year in which the English patent was published.

The Brit patent no. is GB189706220, if anyone is interested.

[Edited on 12-7-2009 by manimal]
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Formatik
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[*] posted on 12-7-2009 at 11:35


Quote: Originally posted by manimal  
I tried "DE98070", but my search was unsuccessful. I'm thinking that there is a special format for entering old patents. Unfortunately, I dont know the year in which the English patent was published.


You can use DEPATISnet if you want the old German patents and don't have the year. As to the British patent, no idea how to get it without the year. Maybe it's referenced somewhere else.
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[*] posted on 12-7-2009 at 11:57


Quote: Originally posted by itchyfruit  
Is cobalt nitrate supposed to be purple ?

It's a deep red colour on wikipedia. . .
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[*] posted on 15-7-2009 at 10:01


The expected melting point of a compound is 189deg.C. When I tested a sample of mine, it melted around 204deg.C.

I remember something from general chemistry stating that impurities would lower the melting point of a compound (though honestly, that doesn't make sense to me if the impurities themselves have higher melting points).

Is the previous claim about impurities always true, or could my sample still be ok (by "ok", I mean, "at least could contain some of the compound")?




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[*] posted on 15-7-2009 at 11:12


Different amount of moisture maybe?

Can you titrate the amount of anion or cation in the material?

Tim




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[*] posted on 15-7-2009 at 13:25


Quote: Originally posted by querjek  
The expected melting point of a compound is 189deg.C. When I tested a sample of mine, it melted around 204deg.C.

I remember something from general chemistry stating that impurities would lower the melting point of a compound (though honestly, that doesn't make sense to me if the impurities themselves have higher melting points).

Is the previous claim about impurities always true, or could my sample still be ok (by "ok", I mean, "at least could contain some of the compound")?



The addition of impurities may lower or raise the melting point of a substance. The addition of chromium to gold can raise the melting point of gold, whereas the addition of about 3% silicon to gold will lower the melting point to about 363° C. Search for "eutectic" on Wikipedia and then check out the the reference link at the bottom of the page:

http://ocw.mit.edu/NR/rdonlyres/Materials-Science-and-Engine...
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[*] posted on 15-7-2009 at 16:42


Quote: Originally posted by manimal  
Since concentrated ammonia solution is so useful but rather scarce, I was thinking that a promising way to prepare it would be to heat intimately mixed ammonium sulfate and calcium hydroxide in a metal can and pipe the fumes into water.


I suppose that to judge the concentration, I can measure the volume increase. I am going for 100% increase in volume, because I intend to heat the CaOH2 and (NH4)2SO4 to a high temperature, and I am taking into account the 2 moles of water released by this reaction (I am heating it that hot to encourage the reaction to go to completion and to liberate the h2o from the CaSO4, which likes to hold onto it's water).
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[*] posted on 15-7-2009 at 16:55


Manimal, maybe better to measure the density of your NH3 soln. in H2O. The density of strong ammonia (28%) is about 0.9 gm/mL. Weigh 10 mL to get an accurate density.

Be sure to cool the water you're absorbing the NH3 in, since absorbtion is exorthermic and NH3 is much more soluble in cold H2O.
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[*] posted on 15-7-2009 at 18:06


Quote: Originally posted by entropy51  
Manimal, maybe better to measure the density of your NH3 soln. in H2O. The density of strong ammonia (28%) is about 0.9 gm/mL. Weigh 10 mL to get an accurate density.


An appropriate volume depends largely on the capabilities of the scale being used. Hopefully, there are some volumetric flasks around as well.




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[*] posted on 18-7-2009 at 14:18


What is a reasonable price for a rotovap with and without glassware? I am looking for one and the best I have seen is about $1200 :o. A little out of my price range but it is in excellent condition w/ glassware.

Any ideas where to get one? Anyone want to get rid of theirs?





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[*] posted on 18-7-2009 at 15:20


I would say about £500 second hand. Varies by make and model, and there are some bargains out there (under £300 I have seen once), as well as some overpriced equipment. Obviously this probably depends on location too.
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[*] posted on 19-7-2009 at 14:43


I want to extract paracetamol from pain medication. (I intend to invistigate it's uses as a polymerization inhibitor). This medicine contains polyethylene glycol, however, which is soluble in water and ethanol. Will the PEG recrystallize w/ the paracetamol after undertaking a water or ethanol extraction?
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