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ACD/Labs Blog

Originally published in 2008, 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 three groups: Structural/Constitutional/Regio, Spin and Stereo/Spatial isomers. Wikipedia links are included...

Structure Elucidator Tutorial Freeware: a free software package at the undergraduate and graduate levels This manuscript covers various exercises of using a free CASE (computer-assisted structure elucidation) software application “Structure Elucidator”. The purpose of these exercises is to use elucidation software to quickly explore potential candidates given a set of NMR data and a molecular...

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...

The nomenclature rules for organic compounds set by the International Union of Pure and Applied Chemistry (IUPAC) committee (http://www.iupac.org/) do offer flexibility in some areas especially in cases where old publications have old terms. Below are some examples. The answers for the structures, as based on the IUPAC nomenclature rules, are listed below. Some links...

Following a successful attempt at solving an unknown, the next step may be to determine a name for the novel compound. The nomenclature rules for organic compounds are set in place by the International Union of Pure and Applied Chemistry (IUPAC) committee (http://www.iupac.org/). For the following compounds, which names adhere to the IUPAC nomenclature rules?

For the past decade, I had the privilege to be involved in a global project aimed at elucidating unknowns from a variety of clients. The purpose of this project was to explore and expand the utility of a Computer-Assisted Structure Elucidation (CASE) software. It is because of this project that the idea for the blog...

Diastereotopic protons that are also anisochronous exhibit different chemical shifts. As a general rule, the proximity of a chiral centre will influence the likelihood of diastereotopic proton signals being anisochronous. For the structure below, the CH2 labeled A is most likely to be anisochronous due to the adjacent chiral carbon. IUPAC: methyl 7-hydroxy-3,5-dioxo-7-phenylheptanoate InChi Key:...

Diastereotopic protons that are also anisochronous exhibit different chemical shifts. The purpose of this puzzle is to understand a general trend for CH2 groups. If the following structure, shown below, were dissolved in CDCl3 and a 1H NMR spectrum were acquired on a 500 MHz instrument, which of the following three CH2’s would most likely...

Based on experience, fused ring systems on an unknown structure tend to conjure up variations of odd connections. The possibilities can seem endless. The diagram, shown below, samples a subset of fused ring systems for a given dataset. It is important to note that although certain systems may be more appealing to the eye, it...

Drug Trials commence with in vitro and in vivo experiments on nonhuman subjects and observing the effects of the candidate drug(s). These are commonly referred to as the pre-clinical trials. Once safe and effective thresholds have been set, the candidate drug(s) can be administered to human subjects and thus begin the clinical trials. The clinical...