which is now a fully balanced equation, although still a pseudo-elementary step and the actual mechanism involves several complex Ti-O-Ti condensation steps. However, the ratedetermining step is the S N 1 step. The first order rate constants were 0.0047 ± 9 • 10 -5 , 0.0044 ± 1 • 10 -4 , and 0.0036 ± 6 • 10 -5 s -1 , for [Ti] = 0.1, 0.2 and 0.3 mol/L respectively. The rate constant is thus independent of the concentration, further strengthening our mechanistic proposal.