Ammonia solution
Ammonia solution, also known as ammonia water, ammonium hydroxide, ammoniacal liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH(aq). Although the name ammonium hydroxide suggests an alkali with composition [NH][OH], it is actually impossible to isolate samples of NHOH. The ions NH and OH do not account for a significant fraction of the total amount of ammonia except in extremely dilute solutions.
Hydroxide
The hydroxide ion may act as a base catalyst. The base abstracts a proton from a weak acid to give an intermediate that goes on to react with another reagent. Common substrates for proton abstraction are alcohols, phenols, amines, and carbon acids. The p"K" value for dissociation of a C–H bond is extremely high, but the pK alpha hydrogens of a carbonyl compound are about 3 log units lower. Typical p"K" values are 16.7 for acetaldehyde and 19 for acetone. Dissociation can occur in the presence of a suitable base.
The base should have a p"K" value not less than about 4 log units smaller or the equilibrium will lie almost completely to the left.