# NMR - coupling of chemically equivalent protons

In Klein's Organic Chemistry 3rd Edition page 671, it states

This observation, called the n + 1 rule, only applies when all of the neighboring protons are chemically equivalent to each other.

However, in the following page, it states

Equivalent protons do not split each other

The first statement infers that for the n + 1 rule to be valid, the protons must be chemically equivalent - inferring that equivalent protons can couple, while the second statement directly contradicts this.

Could my misunderstanding be clarified?

The "n+1" rule refers to a situation where you have a proton of type A with $n$ protons of type B next to it. Proton A's signal will be split $n+1$ times by the B's. However, none of the B's will split each other because they are equivalent.
(There are 2 spins labelled as $\alpha$ or $\beta$, $J$ is the spin -spin coupling constant and $h$ the Planck constant. The energy $A$ is given by $\gamma (1-\sigma)B_0/(4\pi)$ where $\gamma$ is the magnetogyric ratio, $\sigma$ the shielding constant and $B_0$ the static magnetic field).