CHEM 130 Lecture Notes - Lecture 10: Carbon-13 Nuclear Magnetic Resonance, Heterocyclic Compound, Cytosine
Document Summary
Nearby hydrogen nuclei interact and give multiple peaks. So far proton nmr has been not unlike carbon nmr on a smaller scale. This is the result of the interaction between nearby protons known as coupling. An example we could have chosen in the last section is the nucleic acid component, cytosine, which has exchanging nh2 and nh protons giving a peak for hdo at 4. 5 p. p. m. We didn"t choose this example because the other two peaks would have puzzled you. Instead of giving just one line each, they give two lines each doublets as you will learn to call them and it is time to discuss the origin of this coupling". You might have expected a spectrum like that of the heterocycle below, which is also a pyrimidine. It too has exchanging nh2 protons and two protons on the heterocyclic ring. But these two protons give the expected two lines instead of the four lines in the cytosine spectrum.
