Deactivation of water

Excess sulfuric acid serves to shift the equilibrium and thus to speed the reaction by producing a higher concentration of hydrobromic acid. The sulfuric acid also protonates the hydroxyl group of n-butyl alcohol so that water is displaced. The acid also protonates the water as it is produced in the reaction and deactivates it as a nucleophile. Deactivation of water keeps the alkyl halide from being converted back to the alcohol by nucleophilic attack of water. The reaction of the primary substrate proceeds via an Si 2 mechanism. 

The study of the deactivation of water-pretreated Pt/y-Al203 for low-temperature selective CO oxidation in hydrogen./. Power Sources, 124, 415 19. 

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