Analysis of First-Order Patterns

The usual stick diagram conveniently explains the pattern after the fact. However, a first-order pattern resulting, for example, from coupling of a single 

Assign an integer intensity number centered directly under each peak in the pattern, starting with intensity 1 for the outermost peaks. A first-order pattern must have a centrosymmetric distribution of intensities (level a). If it does not, the pattern is higher order. 

The sum of the assigned peak intensities in level a must be 2 , n being the number of coupling protons. In this example, n = 5, which corresponds to coupling of three equivalent neighboring protons and two nonequivalent protons as specified above. 

Draw a vertical line (stick) centered directly under each peak of the pattern, i.e., beneath each intensity number. All lines are drawn to equal height (level b). 

FIGURE 3.35 Cumene (isopropylbenzene) in CDCI3 at 300 MHz. The isopropyl moiety is recognized by the characteristic six-proton doublet and the one-proton septet. 

---