Consider an individual Sq 2-molecule in a high-pH solution. Protonation events are rare. For example, at pH = 10, the protonation rate constant is estimated through equation 28 to be k AB ≃ 1 × 10 -3 s -1 . Hence, at pH=10, a given Sq 2-molecule has to wait for about 1000 s before being protonated, on average.