Hints

 

For those molecules find the number of different signals. We give you the molecular formula in order to guess what are the impurities.

In 1H NMR spectroscopy each signal is composed of 1 or more peaks(multiplet), which inter distances are multiple of the coupling constants. Based on the relative intensities and the separation between peaks, we need to determine how many different signals we can identify in the spectrum.

In order to determine if it is an impurity it is often useful to integrate the spectrum. To integrate, keep pressed the 'ALT' key, while you click on the starting point and on the ending point of the integral.

 

In CDCl3, water is around 1.5ppm and CHCl3 at 7.27.

In DMSO-d6, water is at around 3.5 and DMSO-d5 at 2.5..

Acetone (around 2 ppm) is often an impurity in NMR spectra. It is used to clean the NMR tubes.

If the solvent is not specified, it is CDCl3.

Instructions

 

1. Select an excercise from the left list(Click).

2. Based on the molecular formula and the spectrum, determine the number of different signals in the spectrum that arises from the pure molecule(do not count the impurities/solvent signals).

3. Write your answer in the second column of the left table. You can change the value as many times as you want, but try not to use brute force. Use the evidence in the spectrum.

4. If the answer is correct, the row will be coloured in green.