I am looking for a good reference for 1-13C NMR peaks for Beta-hmb (beta-hydroxy beta-methylbutyrate), and alpha-HIC (alpha-hydroxyisocaprate). I have not been able to find a single experimental instance of 1 carbon Beta-HMB, or aplha-HIC; however, this experimental data is important for proving a hypothesis in a paper I am working on.
Dear Donovan,
it is a good strategy first to search a free NMR database, SDBS for instance (http://sdbs.riodb.aist.go.jp/sdbs/cgi-bin/cre_index.cgi), or look up the Human Metabolome database (http://www.hmdb.ca/). The latter provides, among many other data, references to papers dealing with NMR properties. If this fails, maybe searching your compounds in Scifinder may lead you to original work providing NMR data. Good luck!
Dear Donovan,
Did you record with a bruker spectrometer and are you using topspin (free for academia)? Than you could simply open the dataset and type "xiref" and the procno and expno of an references 1H spectrum. This means, when your 1H spectrum is at expno 10, then you double click on the 13C dataset and type "xiref 10 1" into the commandline. It will return you the "SR" value for your 13C spectrum. This is the spectrum reference value that you have to put ether via the "procpars" tab or by typing sr in the command line. Your 13C spectrum it than referenced using the 1H dataset. Importantly it uses the IUPAC scale. There are different NMR scales!
Many Greetings,
Kristof
Dear Donovan,
as you have enough material for a 13C 1D it must be easy to acquire 2D 1H-13C correlated HSQC and HMBC by which a structure determination of the compounds you mention should be simple....
Kind regards
Alfred
P.S beta-hydroxy beta-methylbutyrate may also run under beta-hydroxy isovaleric acid?
Without knowing the specific structures of the two chemicals in question, it is impossible to predict the exact positions of the 13C NMR peaks. The position of 13C NMR peaks depends on the unique chemical environment surrounding each carbon atom in the molecule, which is determined by the arrangement of other atoms, the type of functional groups present, and the hybridization of the carbon atom.
However, as a general guide, here are some typical 13C NMR chemical shift ranges for various types of carbon atoms in organic compounds:
- Alkanes: 0-50 ppm
- Alkenes: 100-140 ppm
- Aromatics: 110-160 ppm
- Alkynes: 60-90 ppm
- Carboxylic acids: 160-180 ppm
- Esters: 160-180 ppm
- Ketones: 190-220 ppm
- Amides: 160-180 ppm
It should be noted that these are only general trends and chemical shifts may vary depending on the specific compound and the context of the carbon atom in question. A detailed interpretation of 13C NMR spectra requires careful analysis of the entire spectrum, as well as knowledge of the specific chemical structures being analyzed.
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