In the 13 C spectrum, notice that the signals for both C 1 and C 2 are split into doublets by the magnetic field of P A , through 2-bond and 3-bond coupling, respectively. Notice that although the C 1...In the 13 C spectrum, notice that the signals for both C 1 and C 2 are split into doublets by the magnetic field of P A , through 2-bond and 3-bond coupling, respectively. Notice that although the C 1 and C 2 signals were split by P A in our 13 C-NMR spectrum, in the 31 P-NMR spectrum the P A signal is not split by the nearby carbons - this is because, of course, both of these carbons are the NMR-inactive 12 C isotope in 99 out of 100 molecules.
