withoutlaughter
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biphenyl disulfonyl chloride
I tried to recrystalize an reagent called biphenyl disulfonyl chloride. The NMR show corresponding peaks except one around 1.5. I guess it is water. I
attempted several methods to dry it. 1 vacuum+heatgun; 2 tolulene w/ vacuum. But those didnot help much. Right now I try to dissolve it in chloroform
and dry it over MgSO4. Did anyone have better suggestions? Thanks in advance.
[Edited on 20-7-2004 by withoutlaughter]
[Edited on 20-7-2004 by withoutlaughter]
[Edited on 20-7-2004 by withoutlaughter]
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Marvin
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What was the solvent for the NMR?
I'm kinda surprised it didnt hydrolyse, but the acid would be nowhere neer that end Id have guessed.
Did you try just dumping the crystals in a vacuum desicator over P2O5?
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withoutlaughter
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it does not help much by drying over P2O5. The solvent I used in NMR is chloroform, which has a corresponding peak around 7.3. It seems it is not
dissolved in water judged by the wax-like appearance around the bottom of the flask.
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svm
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the water is probably in your chloroform. you might try using a brand new bottle or else try using a different solvent that doesn't soak up
water as easily. maybe benzene.
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withoutlaughter
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| Quote: | Originally posted by svm
the water is probably in your chloroform. you might try using a brand new bottle or else try using a different solvent that doesn't soak up
water as easily. maybe benzene. |
You got the point. I guess so. today I did the NMR to check the chloroform. It did have water in it. Jesus Christ. I never think of it because it is a
new opened bottle.
But I donot think it can dissolve in Benzene due to the polarity.
Herewith highly appreciate the help from you guys. 
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chemoleo
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If water persists to be a problem, why not using D2O? This, as far as I know, won't be detected by the magnet, due to its spin 1 rather than spin
1/2 system.
I am not an expert on this, all I have done is NMR on proteins, and I know for a fact that D2O is used if the signals from H2O become too much of a
problem (i.e. in terms of overlapping peaks).
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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svm
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D2O would hydrolize the chlorides almost immediately. plus D2O would still pick up water from the air, so it doesn't really solve the problem.
does it really matter to you that there is a water peak in the nmr?
[Edited on 22-7-2004 by svm]
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chemoleo
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>D2O would hydrolize the chlorides almost immediately.
Why more so than H2O? Educate me
At least I was never made aware of some adverse chemical effects of D2O - apart from the trouble of growing bacteria in it...
> plus D2O would still pick up water from the air, so it doesn't really solve the problem.
Indeed, but at least in my lab we work under conditions where water/atmospheric gasses have no access - i.e. the NMR tube is closed with a rubber lid,
and the gasses above the sample and between the lid are replaced by argon - so no chance of H2O contamination. Thats how we get our samples to work
despite a rather large cysteine content (which may produce SS bridges, thus aggregation, thus relaxation problems)
[Edited on 22-7-2004 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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svm
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it wouldn't be hydrolizing any faster than in water, but the difference is concentration. there is just a trace amount of water in the
chloroform, but there is more than a trace in the D2O!
I was just saying that for practical considerations the D2O will soak up water from the air while it is stored on the shelf. I haven't done any
nmr in D2O but I thought that the water peaks were larger in D2O than they were in organic solvents. you would know better than I would.
aren't there some special water-supression experiments that you can do? I think I have heard of those before.
[Edited on 22-7-2004 by svm]
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withoutlaughter
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I dont know much about it. But I owns a bit warming bias to organic solvent. Today I try to dry the chloroform through a simply made column which has
drying agent in it w/ argon. But there is still a water peak there. It seemed the peak got a bit lower. But I still cannot know if there is water in
my stuff. Did you guys know how to calculate the intensity of the peak w/o reference. I could know if there is water in my sample w/ the negative
control. I will try D2O, but as far as i know, the solubility is a problem.(very low)
[Edited on 22-7-2004 by withoutlaughter]
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svm
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I'm not at all sure about this, but I think you can take an nmr of your chloroform with no sample in it, integrate the water peak relative to the
chloroform peak to get the ratio. then run an nmr with you sample in chloroform from the same bottle. integrate the chloroform peak relative to the
water peak again and see if the integration from the blank run and the run with your sample are the same.
does anyone see a reason that wouldn't work? I'm not sure....
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chemoleo
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Hmmm, I see.
Just remembering my knowledge in protein NMR, I recall that water peaks are commonly suppressed (at 55 molar the corresponding peak is obviously
monstrous). I don't know the technique for it, but I never needed to deal with the problem of water, in 1, 2 or 3D NMR. I used deuterated buffers
though.
As to water peak suppression - I am sure this is some mathematical process, which you can probably find somewhere on the internet... or in NMR
textbooks. Really though, the 'experts' operating the NMR machine should know about this!
[Edited on 22-7-2004 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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sheldonwhite
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| Quote: | Originally posted by svm
D2O would hydrolize the chlorides almost immediately.
[Edited on 22-7-2004 by svm] |
Actually Arylsulphonyl chlorides are fairly resistant to hydrolysis, certainly in cold water. They are quite insoluble in water, for one thing.
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