Bromothymol blue forms a green solution when dissolved in water but turns blue if KOtBu is added to the solution. Explain.

KOtBu acts as an acid because it is the conjugate base of an alcohol that is a stronger acid than bromothymol blue, protonating it and transforming it to its blue form.

KOtBu acts as a nucleophile that severs the C-O bond on its yellow form and transforms it to its blue form.

KOtBu acts as a nucleophile that forms the carbonyl bond to transform it into its blue form.

KOtBu acts as a base because it is the conjugate base of an alcohol that is a weaker acid than bromothymol blue, deprotonating it and transforming it to its blue form.