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Spectrum-to-Structure Integration – What is it?

One of the unique features that ACD/Labs software has embraced over the years is something called spectrum-to-structure integration.

It’s the idea of not only attaching a chemical structure to a piece of analytical data but to also assign that data to pieces of the chemical structure.

This topic gives me a good opportunity to show you one of the new additions in version 11 of ACD/1D NMR Processor (and ACD/1D NMR Assistant) and to perhaps emphasize my point.

I have blogged about the ability to create a multiplet report before, but now in version 11, enhancements have been added. It is now possible to select from a list of pre-formatted templates for multiplet reports based on official journal and patent formats:

Jnatp

Furthermore, you can also create a report of a different format defined by you, the user:

Userdef_2

To get back on topic let’s look at a formatted multiplet report for the Journal of Natural Products:

1H NMR (400MHz, DMSO-d6) d = 10.40 (1H,
br. s., H-13), 8.49 (1H, t, J = 5.5 Hz, H-10), 7.63 (2H, d, J5, 3,6, 2
= 8.7 Hz, H-5, 3), 6.54 (2H, d, J6, 2,5, 3 = 8.7 Hz, H-6, 2), 5.69
(2H, s, H-7), 3.58 (2H, q, J = 6.0 Hz, H-11), 3.04 – 3.25 (6H, m,
H-16<”>, 14<”>, 12, 16<‘>, 14<‘>), 1.22 (6H, t, J =
7.2 Hz, H-17, 15)

The thing I really like about the Journal of Natural Products report is that it includes the assignments in their multiplet report (see assigned atom labels in bold).

This is a nifty time-saving feature, but more on my point regarding spectrum-to-structure integration, notice that the software assigns an experimental multiplet. Not a peak in a multiplet nor a region of the spectrum.

Within ACD/1D NMR Processor or ACD/1D NMR Assistant, users can assign experimental multiplets, meaning that when assigning an atom to the spectrum it is associating the multiplet and all of it’s properties (including chemical shift, coupling constants, integration values, etc.)

This of course becomes incredibly important when considering software for automated structure verification. ACD/Labs’ solution is not just based on chemical shift prediction, but also on observed and predicted multiplet characteristics, and integration information.

It is these characteristics that are important in the implementation of the algorithms used in tools such as ACD/1D NMR Assistant, ACD/1D NMR Expert, and ACD/2D NMR Expert.

When evaluating different NMR software packages, keep an eye out for true spectrum-to-structure integration.

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