# How does monoethanolamine (MEA) increase pH?

I know pH of a solution increases with increase concentration of $$\ce{OH-}$$.

I'm wondering: when adding MEA, is the $$\ce{OH-}$$ group from the MEA breaking off, or is it the whole MEA molecule taking a hydrogen from $$\ce{H2O}$$ leaving the $$\ce{OH-}$$?

• Nitrogenous bases work as Brønsted bases because the nitrogen can pull a proton from water to produce hydroxide. – Zhe Mar 18 at 16:32

It is the latter case where "the whole MEA molecule is taking a hydrogen from $$\ce{H2O}$$ leaving the $$\ce{OH-}$$". Alcohols very seldom acty as arrhenius bases adding $$\ce{OH-}$$ to solution. One exception is triphenylmethanol but I cannot think of a second that isn't a variation of the given example. Instead the unbonded electron pair of the amine will abstract a hydrogen from water to form an ammonium ion leaving a hydroxide counter ion and thus raising the pH.