In this section we will learn how to create spin system from molecule strucure. In this tutorial we have a simple aromatic molecule p-bromochlorobenzene.

As we can see the spectrum is very simple. To create spin system and chemical shifts from the molecule structure right click the structure and 'Nmr prediction...'.

The default options are usually suitable as in this case.

Nmr predictor created spin system with two chemical shifts. There seems to be some systematic error so the chemical shifts should be dragged to correct positions.

Note also that the 'spin particle' type is 1*2*1 for both shifts. This allows different J-couplings between each coupled proton. In the picture below there are marked the possible J-couplings of particle 'A'.

There is also J-coupling between protons 'B' and "B'" so all the couplings of this molecule can be defined with four coupling constants. The initial J-coupling matrix looks like this:

The shift '4_5' corresponds to protons 'A' and "A'" in the earlier picture.

Next we can simulate the spectrum.

Zoom into the region where the chemical shifts are and then simulate with ctrl+R. If you dragged the shift labels approximately on the observed shifts the result should be almost like this:

The initial guesses for the J-couplings looks pretty fine. Now we can match the calculated shifts more accurately with the observed shifts by dragging the labels. Note the appearing stick spectrum when shift is selected. With the help of it we can match the calculated spectrum to the observed one.

After simulation the spectrum should look like this.

Now we are ready to iterate the parameters.

Iterate the spectrum with ctrl+T. The result should look like this:

And we are ready with this analysis!