hydration of alkenes (1 Viewer)

[NexusRich]

Why is high temperature and pressure required for the hydration of alkenes? and also why specifically phosphoric acid being used as a catalyst, would other acids not work ?

 

[CM_Tutor]

Hydration of alkenes is an equilibrium process:

RCH=CH₂ + H₂O <---> R-CH(OH)-CH₃

It is acid catalysed so yes, any acid will work in theory... but in practice, if the acid is HX (X = Cl, Br, I, ...), there is a competing addition process. If sulfuric acid is used, it must be dilute as conc H₂SO₄ absorbs water and so draws the equilibrium position to the left. In gas phase, the catalyst acid will be present in unionised form so sulfuric acid will be inappropriate.

It need not be high T and P if the reaction is carried out in solution, though will be for a reaction carried out in gas phase (ie. if the alkene is a gas and not soluble in a convenient solvent). High P pushes the equilibrium right (by Le Chatelier's Principle). High T will be because the reaction is slow or endothermic or both.