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Although ca. 1 mln. times less sensitive than 1 H NMR spectroscopy, 13 C NMR spectroscopy is widely used for characterizing organic and organometallic compounds, primarily because 1H-decoupled 13C-NMR spectra are more simple, have a greater sensitivity to differences in the chemical structure, and, thus, are better suited for identifying ...
SDBS includes 14700 1 H NMR spectra and 13000 13 C NMR spectra as well as FT-IR, Raman, ESR, and MS data. The data are stored and displayed as an image of the processed data. Annotation is achieved by a list of the chemical shifts correlated to letters which are also used to label a molecular line drawing.
If a spectrum of an unknown chemical compound is available, a reverse search can be carried out by entering the values of the chemical shift, frequency or mass of the peaks in the NMR, FT-IR or EI-MS spectrum respectively. This type of search affords all the chemical compounds in the database that have the entered spectral characteristics. [6]
13 C NMR Spectrum of DMSO-d 6. Pure deuterated DMSO shows no peaks in 1 H NMR spectroscopy and as a result is commonly used as an NMR solvent. [2] However commercially available samples are not 100% pure and a residual DMSO-d 5 1 H NMR signal is observed at 2.50ppm (quintet, J HD =1.9Hz). The 13 C chemical shift of DMSO-d 6 is 39.52ppm (septet ...
Nuclear magnetic resonance chemical shift re-referencing is a chemical analysis method for chemical shift referencing in biomolecular nuclear magnetic resonance (NMR). [1] It has been estimated that up to 20% of 13C and up to 35% of 15N shift assignments are improperly referenced.
[5] In this common practice, users adjust residual solvent signals of 1 H or 13 C NMR spectra with calibrated spectral tables. [6] [7] If substances other than the solvent itself are used for internal referencing, the sample has to be combined with the reference compound, which may affect the chemical shifts.
The HSQC experiment is a highly sensitive 2D-NMR experiment and was first described in a 1 H— 15 N system, but is also applicable to other nuclei such as 1 H— 13 C and 1 H— 31 P. The basic scheme of this experiment involves the transfer of magnetization on the proton to the second nucleus, which may be 15 N, 13 C or 31 P, via an INEPT ...
Because of the magnitude and severity of the problems with chemical shift referencing in biomolecular NMR, a number of computer programs have been developed to help mitigate the problem (see Table 1 for a summary). The first program to comprehensively tackle chemical shift mis-referencing in biomolecular NMR was SHIFTCOR. [2] Table 1.