July 28, 2008
by Arvin Moser, Team Manager, Application Scientists, ACD/Labs
Like a COSY experiment, an HMBC dataset offers many combinations of atom connectivity. The goal for the elucidator is to assess each correlation and narrow down a set of fragments that support the data.
For every correlation in a 1H-13C HMBC spectrum, an elucidator must decide whether a correlation corresponds to a 2J, 3J or 4J coupling (NOTE: this is dependent on what the coupling constant is set to in the HMBC sequence). Below is a structural list for all H to C connections—heteroatoms are not shown in the list for the sake of simplicity. The 2J coupling, outlined with a blue box, the 3J coupling, outlined in a green box, and the 4J coupling, outlined with a purple box, offers 3, 6 and 14 possible combinations, respectively.
Dear Arvin,
I am a student in Brazil. I use ACDLabs and I am a fan of you Blog. Then, I have a question.
In an HMBC experiment (see image file) of a very small sample of isorhamnetin-3-O-glucoside was only observed a single sign of the correlation between the hydrogens of the methoxyl group (s,4.05) and carbon C-3 ‘(148.29). How can I explain this?
Thank you in advance.
Best Regards
—
Djalma Menezes de Oliveira
Natural Products Researcher
Researcher groups: NEPLAM-UFMG, NUPRONAT-UESB
Phytochemistry area
Blog: http://fracionamento-silicagel.blogspot.com/
Hello Djalma,
Thank you for taking an interest in the blog P2C2E.
Based on your HMBC data, I suspect the correlation at 4.06/148 ppm is a result of 3J(H-C) coupling.
HMBC Interpretation: http://acdlabs.typepad.com/elucidation/2008/07/interpreting-a.html
Regards,
Arvin
Shaylee Whitman
Muchos Gracias for your blog article. Fantastic.
Sir,I am having H,C,HMBC,HSQC spectra of a compound isolated from a plant.Would you able to interpret the spectra.with regards,Deepa,
Sir,I am having H,C,HMBC,HSQC spectral data of a molecule isolated from a bacteria.Would you please help to interpret the spectra.with regards
Hello Mohd,
At ACD/Labs, we offer a paid service for solving unknowns at http://www.acdlabs.com/products/com_iden/elucidation/struc_eluc/challenge.php.
Regards,
Arvin