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ACD/Labs Blog

Arvin Moser
Due to their broad peaks and wide range of chemical shifts in 1H NMR spectra, exchangeable protons are known to pose challenges in NMR interpretation, but collecting 2D spectra and selecting proper experimental conditions can sometimes be used in our favor to learn more.

Sanji Bhal
1H NMR is the go-to technique to help identify or confirm the structure of organic compounds. A solution-state proton spectrum is relatively fast to acquire and a lot of information about the structure of a compound can be deduced from it. With centuries of combined experience in NMR data interpretation, we thought we’d share the basics of analyzing solution-phase 1H NMR spectra in this blog.

Arvin Moser
In collaboration with Sequoia Sciences Inc., we developed a strategy for the dereplication of a complete or a partial structure using 1H NMR, 1H–13C HSQC and 1H–1H COSY spectral data, a molecular formula composition range and structural fragments against a massive database of about 22 million compounds is considered. The work was based on 18...

Arvin Moser
Instruments can fail mechanically and when they do fail, it is important to recognize the signs. For NMR data, any irregularities in the baseline can indicate an instrument issue. The best strategy to minimize instrument failures is to perform regular maintenance and collect data for standards with well documented results prior to any data collection....

Arvin Moser
Part 1 presented a challenge to determine an experiment to distinguish two very similar products from each other, namely 3-methyl-5-(pyridin-2-yloxy)pyridine and 5′-methyl-2H-1,3′-bipyridin-2-one. The products have identical formula weights and the LC/MS and 1H NMR are too similar to draw any conclusion from. The first step is to determine what is different between the two products...

Arvin Moser
Many organic chemists—if not all—check to see if a synthetic reaction is complete via TLC and LC/MS and/or 1H NMR. At the same time, the chemists are using the analytical data to verify that the final product is what they intended on making. In some cases, LC/MS and 1H NMR do not adequately distinguish one potential product...

Arvin Moser
Sugar residues (saccharides) can be tough to elucidate. They tend to have 1H NMR spectrum with overlapping and sometimes poorly-resolved 1H signals, and the 2D NMR data presents lots of ambiguous assignments. With a little practice, an elucidator can quickly pick out a sugar moiety based on a minimal amount of NMR data. For a...

Arvin Moser
Where a COSY or TOCSY spectrum can be a challenge for a structure with severe spectral overlap, collecting an HSQC-TOCSY spectrum can be a better choice. An HSQC-TOCSY experiment stands for Heteronuclear Single Quantum Coherence-Total Correlation Spectroscopy and other variants include HMQC-TOCSY, HSQC-COSY, etc. Depending on the mixing time, the hybrid experiment generally offers information...

Arvin Moser
Part 1 of the series Teaching and Learning by Spectral Data explored the difference between presenting an NMR problem set to a student in the form of an alphanumerical text or as an actual NMR spectrum. Continuing on the same problem set, another issue arises. Is the information on the elements and the 1H NMR...

Arvin Moser
There are many ways to teach the process of elucidating unknown structures. Offering a student a visual guide, such as seeing firsthand a spectral dataset, can enhance the learning process and better equip the student on future work. Presented below is a typical elucidation question from a university test. The numerical values have been extracted...