47th PPNMR Conference – Practical Problems in NMR Spectroscopy

Julia Volk [a], Dimitris Argyropoulos [a], Sergey Golotvin [a], Maxim Kisko [a], Mikhail Elyashberg [a]

[a] Advanced Chemistry Development (ACD/Labs), Toronto, ON, Canada

Over the last several decades, computer assisted structure elucidation (CASE) has become a proven method [1] for the unambiguous determination of new chemical structures from NMR data paired with a molecular formula. CASE offers many benefits over manual elucidation, including efficiency and the elimination of human bias. However, despite significant advances in computing power over its lifetime, it still takes time for CASE to generate and assess all the possible structures. In many cases, this is only a few seconds to minutes. Nonetheless, when NMR information is ambiguous or limited, elucidations can take hours or even days to complete.

In this presentation, we will explore the various options available to identify simple fragments, such as carbonyl as well as mono– and para-substituted aromatic rings, of the structure being elucidated. We will then use the identified fragments to generate modified Molecular Connectivity Diagrams that allow for much faster structure generation, and thus, elucidation in significantly less time in some cases.

We will also explore the options of searching for fragments in either fragment libraries or databases of complete structures, like PubChem. These offer the benefit of identifying more complex fragments that could represent 50% or more of the structure, leading to very significant reductions in the elucidation time.

Finally, we will discuss some AI tools that are being developed and offer the benefit of very rapid fragment identification or complete structure elucidation with minimal spectral input.

1. E. Elyashberg, A.J. Williams. “Computer-based Structure Elucidation from Spectral Data. The Art of Solving Problems”, Springer, Heidelberg, 2015, 454 p.