The importance of the role played by solvent in this reaction becomes obvious when you consider that acetic acid, when reacting with water in the gas phase, has a measured pK a value greater than 100!...The importance of the role played by solvent in this reaction becomes obvious when you consider that acetic acid, when reacting with water in the gas phase, has a measured pK a value greater than 100! (Recall that the pK a of acetic acid in water is 4.8). The pK a -lowering effect of a metal cation can be dramatic – it has been estimated that a water molecule coordinated to a Cu +2 or Zn +2 ion can have a pK a as low as 7 (compare this to the ‘normal’ water pK a of 15.7!) (J.
