CH 9-5: NMR Topic 3 - “Signal Splitting” The magnetic field of a specific H nucleus will be “influenced” by the H nuclei on adjacent carbon atoms. This causes the single line of a H signal to be “split” into 2, 3, 4, or more lines. N + 1 Rule to predict 1H NMR signal splitting: If “N” is the total number of H’s on all carbons adjacent to a specific H, then the signal from H will be “split” into N + 1 lines = 4 (quartet) N + 1 = signal splitting = 2 (doublet) N + 1 = signal splitting

NMR “Signal Splitting” for observed H N = 0N+1 = 1singlet (s) N = 1N + 1 = 2doublet (d) N = 2N + 1 = 3triplet (t) N = 3N + 1 = 4quartet (q) N > 4N + 1 > 5multiplet (m) N + 1 = signal splitting N = total of all H’s directly adjacent to H:

Example: Isopropylmethyl ether How many signals? What is the signal splitting? (b) (a) (a) (c) H nuclei# protons Splitting n+1 rule (a) (b) (c) d m s

Isopropylmethyl ether (a) (b) (c) (b) (a) (a) (c)

CH 9-5: NMR Topic 3 - “Signal Splitting” You should be able to answer the following question: Complete the following table for each set of protons in the molecule shown below: H nuclei# protons Splitting n+1 rule