Skip To Content

ACD/Labs Blog

Arvin Moser
Many new medicinal drugs produced by pharmaceutical companies follow a very similar pathway starting from the inception of the project idea and ending at the shelves of a pharmacy. Each stage in the development of the drug involves various types of chemists, each lending their expertise at synthesizing, extracting, analyzing and testing the new drug....

Arvin Moser
Whenever a GC column is used to identify and/or quantify a sample, the column stationary phase can bleed into the MS source along with the sample. High column bleed can hinder the analysis of a sample. The resulting spectral interference typically manifests itself as discrete peaks and/or an increase in the drift of the baseline, which...

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
There are many challenges present in deciphering correlations on an HMBC experiment. Barring any data collection issues, most of the challenges will arise from signals that are overlapping, thus, adding an element of ambiguity. The 1H -13C HMBC spectrum below shows a correlation between the 13C at 71.2 ppm and the overlapping 1H signals at...

Arvin Moser
TLC (Thin Layer Chromatography) offers a simple approach to identifying a solvent(s) for separating out a mixture, monitoring a reaction to completion, etc. Furthermore, the TLC plates can be stained to identify the presence or absence of various functional groups such as amines, ketones, etc. This qualitative experiment does offer various drawbacks. The process of...

Arvin Moser
Functional groups such as allene (C=C=C) and cumulene (C=C=C=C) present an interesting challenge in an elucidation project, especially when an elucidator is not expecting them. The 13C chemical shifts for allene carbons are typically expected at 80, 200 and 100 ppm +/- ~20 ppm per shift. The confusion, or better described as bias, arises at...

Arvin Moser
The line shape of a peak on a chromatogram can offer some insight into the presence of a functional group. However, issues with the instrument are also known to affect the line shape for a peak. The GC/MS EI+ Total Ion Chromatogram/Current (TIC) below shows five peaks. All of the peaks with the exception of...

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...