Which Is More Acidic?
Molecule A
Molecule B
Which is more acidic?
Common Questions
What is pKa?
pKa is the negative log of the acid dissociation constant (Ka). A lower pKa means a stronger acid that more readily donates a proton. Each unit decrease in pKa represents a 10-fold increase in acidity.
How do you compare acid strength using pKa?
The compound with the lower pKa is the stronger acid. Compare pKa values directly: an acid with pKa 4 is 1,000 times stronger than one with pKa 7.
What factors affect pKa?
Electronegativity of the atom bearing the charge, resonance stabilization of the conjugate base, inductive effects from nearby electron-withdrawing or donating groups, hybridization of the orbital (more s-character = more acidic), and aromaticity of the conjugate base.
What is DMSO and why measure pKa in it?
DMSO (dimethyl sulfoxide) is an aprotic solvent that does not hydrogen-bond to anions. Measuring pKa in DMSO reveals intrinsic acidity differences that can be masked in water by strong solvation of small anions.