Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: rubymelia on 25/11/2018 21:34:51
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When would you prefer to use d-DMSO over CDCl3 when submitting a H NMR sample? Is there any difference? Thanks
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The obvious answer is when your sample dissolves in D6 DMSO, but not in CDCl3
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DMSO is a much better solvent that chloroform (much more polar and more polarizable than chloroform, and a potent hydrogen bond acceptor to boot)--there aren't many molecular substances that aren't soluble in DMSO, at least enough to get a decent NMR (it's ok for some polymers and some salts as well).
Major disadvantages of DMSO with respect to chloroform: dmso is much less volatile than chloroform (it is very easy to remove chloroform from a sample by distilling it off at low pressure--once dissolved in dmso, there are very few ways to recover a sample), dmso has a very high freezing point (19 °C vs –64 °C for chloroform, so no low-temp VT studies), dmso will absorb moisture from the atmosphere while chloroform will not, substances dissolved in dmso can pass through the skin quite easily, so one must be EXTREMELY careful about handling toxic substances in dmso, and finally, cost (dmso is about 15% more expensive, which isn't crazy, but adds up).
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Oh, another thing to consider: the residual protiated solvent peak of chloroform shows up at 7.26 ppm, and dmso shows up at 2.5 ppm, so sometimes the choice can be made based on which part of the spectrum you need to look at.
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The information provided is very useful to me.