For 10 points, name this parameter used to measure acidity, the negative log of the dissociation constant.
[NOTE TO MODERATOR: alkyne rhymes with fine] In one palladium-catalyzed allylation between an allyl bromide and a nucleophile (NEW-klee-oh-file), this parameter determines whether the nucleophile attacks the allyl bromide directly or coordinates to the palladium catalyst. That is the Tsuji-Trost (SOO-jii-trost) reaction. Cross-coupling reactions involving sp3-hybridized carbons experience an increase in reaction rate when this parameter decreases. Due to the shape of sp orbitals, terminal alkynes have a value of this around 25. Averaging this variable for some pair of the side chain, the amine group, or the (*) carboxyl group is used to calculate the isoelectric point of an amino acid. This value increases for every successive de-protonated species of a poly-protic acid. At the half-equivalence point on a titration curve, this value is equal to the pH. For 10 points, name this parameter used to measure acidity, the negative log of the dissociation constant.
[NOTE TO MODERATOR: alkyne rhymes with fine] In one palladium-catalyzed allylation between an allyl bromide and a nucleophile (NEW-klee-oh-file), this parameter determines whether the nucleophile attacks the allyl bromide directly or coordinates to the palladium catalyst.
pKa [prompt on things like "acid strength" or "acidity," accept Ka until "parameter decreases"]