Validation of a ¹H spectrum

The command View > Comparison can be used to validate a 1-D spectrum against a list of predicted chemical shifts. This page explains how to validate a ¹H spectrum. Click here for the ¹³C validation workflow.

Hydrogen chemical shifts can be predicted with varying degrees of accuracy, either through empirical rules or neural networks.
You can do this in many ways, for example by consulting a book. iNMR offers a fast and simple workflow.
The chemical shifts are calculated by nmrdb.org (Universidad del Valle, Colombia). With an extra effort you can replace it with the predictor of your choice.

To Validate a ¹H Spectrum:

  1. Process the spectrum as usual. Correct the phase and calibrate the frequency scale if necessary. Correct the baseline, perform peak-picking and integration. The essential step is to populate the J Manager with the values of chemical shifts and, if possible, coupling constants.
  2. Insert the SMILES code of your compound in the Edit > Metadata dialog. If the option “Call Open Babel” is on, the SMILES code is automatically generated when you paste a ChemDraw formula or drag a MOL file.
  3. Invoke the menu command View > Prediction. This will open the NMR predictor in your default browser. On that page look for the table on the right called “List of Signals”. At the top-right of the table there is a little rectangular icon. Right-click or control-click.
  4. A menu will appear. Choose “Export”. The same table will appear in its own window. Copy the list of predicted chemical shifts and J values. This is an example of what you can copy: 
    	 0.9	6	d	 6.59 
	1.897	1	tp	 6.76 6.59 
	2.416	2	dd	 6.89 6.76 
	9.643	1	t	 6.89
    It does not matter if you also copy the header. In practice, the simplest thing is to copy the whole content.
  5. Return to iNMR. Invoke the menu command View > Comparison. This will compare the experimental data with the predictions stored in the clipboard.
  6. The results quantify the agreement, but the final scientific judgment remains with the user. iNMR cannot tell if the prediction is accurate. What iNMR measures is the agreement between the two lists. A good agreement does not prove that the structure is correct.

The predictor also provides assignments. You can store this additional information in your iNMR document, either with comments or with the J Manager.

Related Topics

Adding your Annotations to a Spectrum

Validation of a ¹³C spectrum

Adding the Structural Formula

Web Tutorial

video