TABLE 3.

pK of acids in water and bimolecular rate constants at 20°C, pH 5.0

	pK*	ΔpK	kq, M−1 s−1†	kq, M−1 s−1‡
Acetic acid <0.1 M	4.76	−3.34	8.50 × 108	–
Acetic acid 0.1 M		−3.34	6.9 × 108	6.8 × 108
Acetic acid 0.5 M		−3.34	4.1 × 108	6.1 × 108
Acetic acid 1 M		−3.34	3.1 × 108	5.9 × 108
Acetic acid 2 M		−3.34	1.2 × 108	5.5 × 108
Monochloroacetic acid	2.85	−5.25	7.65 × 109	–
Lactic acid	3.86	−4.24	2.03 × 109	–
Cacodylic acid	6.19	−1.91	7.96 × 107	–
H3PO4 0–0.1 M	2.12	−5.98	1.54 × 1010	–
H3PO4 0.1–0.6 M		−5.98	2.63 × 1010	2.2 × 1010
H3PO4 0.6–1.0 M		−5.98	3.79 × 1010	–
H3PO4 1–1.5 M		−5.98	5.47 × 1010	4.6 × 1010
	7.21	−0.89	1.07 × 107	–

^*The pK values are obtained from the CRC Handbook of Chemistry and Physics (32).

^†Values obtained from steady-state measurements.

^‡Values obtained from time-resolved measurements.