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ACD/Labs Blog

Arvin Moser
The approach behind solving a structure elucidation problem is very similar to attempting a math problem or working on a jigsaw puzzle. This similar mental framework shares a basis, but not limited to, on understanding the basic rules that define the problem, and in some cases the creativity and flexibility to redefine the problem. When...

Arvin Moser
A previous blog described the Internet as a valuable tool in searching for previous work based on a molecular formula. In addition to searching the Internet “directly”, certain online sites can assist and facilitate the search process. Some of these sites are free while others have a fee. Be aware that the Internet is full...

Arvin Moser
Searching for unknowns across an internal library or database can serve as a major time saver. A more accessible database is the Internet. Many chemists and elucidators search the World Wide Web using a mass, a molecular formula or a fragment. Be aware that proprietary data sent over the Internet runs the risk of being...

Joel Michalski
The reliable determination of stereocenters contained within chemical structures usually requires utilization of NMR data, chemical derivatization, molecular modeling, quantum-mechanical (QM) calculations and, if available, X-ray analysis. In this article, we show that the number of stereoisomers which need to be thoroughly verified, can be significantly reduced by the application of NMR chemical shift calculation...

Arvin Moser
I would like to begin the new year with a weblog that summarizes the components of an elucidation process. Each component, shown as a Venn-like diagram below, can blend in with the next until a conclusion is reached. The goal for the elucidator is to exhaust all aspects of each possible component thus ensuring that...

Arvin Moser
Infrared (IR) spectrometry is an excellent diagnostic tool for identifying, or lack of, a carbonyl functional group(s). Carbonyl stretching vibration absorbs between 1900-1600 cm-1—a region where few other functional groups absorb. In addition, the carbonyl vibration is typically intense and thus easy to spot. The gas phase FT-IR spectra, shown below, represent five carbonyl bands...

Arvin Moser
Infrared (IR) spectrometry can serve as a simple method to gather information on the presence of OH. Characteristic OH absorptions occur around the ranges of 3700-3200 cm-1 (OH stretching) and 1200-1000 cm-1 (OH bending). In the case of hydrogen-bonded OH, the band in the region 3700-3200 cm-1 generally appears broad and sometimes can go unnoticed....

Arvin Moser
The progression of a structure elucidation process is to examine the experimental data, compare the results to literature if possible, build a set of fragments based on the available data and finally assemble the fragments until a candidate structure(s) is reached. The assembly part is very much like working on a jigsaw puzzle. When all...

Arvin Moser
The underlying essence of a structure elucidation process is to structurally distinguish an unknown from a set of possible isomers. This is evident by the number of possible isomers for a given molecular formula. The chart below divides isomers into two groups: Structural/Constitutional/Regio and Stereo/Spatial isomers. Wikipedia links are included for further reading into the...