¹³C NMR: ¹H–¹³C Decoupling

The low natural abundance of carbon-13 results in a negligible probability of there being two adjacent carbon-13 atoms, practically eliminating carbon–carbon J-coupling.

However, neighboring protons split the carbon signal according to the n+1 rule.

These complex signals are simplified by the broadband proton decoupling technique.

In this method, one transmitter produces radio frequency pulses that cause carbon-13 resonance.

A second transmitter generates a continuous broadband of radio frequencies that cause all the protons to flip rapidly between their two energy states.  

So, the carbon-13 nuclei sense one average field from the protons, nullifying the spin-spin interactions.

The carbon-13 signals are now decoupled from the protons, and the peaks are not split into multiplets, as seen in the proton decoupled spectrum of 1-hexanol.