The appearance of the 1H NMR signals of protic samples in aprotic solvents depends critically on the concentration of the sample. The -OH, -NH2 or -COOH signals can have chemical shift values and line widths over a wide range due to varying extents of hydrogen bonding and chemical exchange. The concentration can also determine whether or not one is able to observe J coupling between and -OH proton and other protons in the sample. An example of this is illustrated below. The figure shows the spectrum of methanol in deuterated acetone. The spectrum on the top is that of concentrated methanol and it consists of two singlets. In this case the methanol molecules are hydrogen bonded to one another and the -OH protons are undergoing fast exhange with one another. The spectrum on the bottom is that of very dilute methanol. It is a second order spectrum with two signals approximating a doublet and a quartet due the J coupling between the methyl protons and -OH proton, respectively. Note that the chemical shift of the -OH proton is much lower for the dilute methanol compared to the concentrated methanol. In this case the methanol molecules are not hydrogen bonded to one another and there is no (or very slow) exchange among the -OH protons between molecules allowing for the observation of the J coupling.
[Stan NMR blog] Storing d-chloroform and other NMR solvents
Storing d-chloroform and other NMR solvents
A few recommendations collected from literature and internet
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02-13-2011 08:54 PM
[NMR paper] Measuring enzyme hydration in nonpolar organic solvents using NMR.
Measuring enzyme hydration in nonpolar organic solvents using NMR.
http://www.ncbi.nlm.nih.gov/corehtml/query/egifs/http:--www3.interscience.wiley.com-aboutus-images-wiley_interscience_pubmed_logo_120x27.gif Related Articles Measuring enzyme hydration in nonpolar organic solvents using NMR.
Biotechnol Bioeng. 1995 Jun 5;46(5):452-8
Authors: Parker MC, Moore BD, Blacker AJ
A very sensitive NMR method has been developed for measuring deuterated water bound to proteins suspended in nonpolar solvents. This has been used to determine the amount of...
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08-22-2010 03:41 AM
[Stan NMR blog] Storing d-chloroform and other NMR solvents
Storing d-chloroform and other NMR solvents
A few recommendations collected from literature and internet.
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08-21-2010 05:42 PM
[NMR paper] Structure of lysozyme dissolved in neat organic solvents as assessed by NMR and CD sp
Structure of lysozyme dissolved in neat organic solvents as assessed by NMR and CD spectroscopies.
http://www.ncbi.nlm.nih.gov/corehtml/query/egifs/http:--www3.interscience.wiley.com-aboutus-images-wiley_interscience_pubmed_logo_120x27.gif Related Articles Structure of lysozyme dissolved in neat organic solvents as assessed by NMR and CD spectroscopies.
Biotechnol Bioeng. 1999 Apr 20;63(2):242-8
Authors: Knubovets T, Osterhout JJ, Klibanov AM
The structure of the model protein hen egg-white lysozyme dissolved in water and in five neat organic...
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08-21-2010 04:03 PM
NMR solvents and chemical shifts ranges
NMR solvents and chemical shifts ranges
Provides a list of commonly used NMR solvents and their physical properties. Also contains typical chemical shift ranges for different types of nuclei
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