Values for k_DO, k_HO, and pK_as of the DKPs studied at 25 °C and I = 1.0 M (KCl).

	k DO (M−1 s−1)	k HO b (M−1 s−1)	k rel c	pKad
c(Gly–Gly)	6.33 × 10−2	3.17 × 10−2	12.2	20.9
c(l-Ala–l-Ala)	7.80 × 10−3	3.90 × 10−3	3.00	22.7
c(Gly–l-Pro)	1.87 × 10−1	9.35 × 10−2	144	18.8
c(H2-Gly–l-Pro)	2.09 × 10−2	1.05 × 10−2	16.2	21.2
c(H3-Gly–l-Pro)	6.59 × 10−2	3.30 × 10−2	50.8	19.9
c(d-Ala–l-Pro)	9.45 × 10−2	4.73 × 10−2	72.8	19.6
c(d-Ala–l-Pro)	5.51 × 10−3	2.76 × 10−3	4.25	22.6
c(d-Pro–l-Pro)	9.69 × 10−2	4.85 × 10−2	37.3	20.0
c(d-Pro–d-Pro)	8.62 × 10−3	4.31 × 10−3	3.30	22.6
c(l-Pro–l-Tyr)	1.19 × 10−1	5.95 × 10−2	91.5	19.3
c(l-Pro–l-Tyr)	2.09 × 10−3	1.05 × 10−3	1.60	23.7
	2.6 × 10−3	1.3 × 10−3	1.00	23.9

^aH/D-exchange kinetic data for N-acyl glycyl amide, a linear analogue of a DKP, is included for comparison.⁴⁸

^bCalculated from experimental k_DO values using a secondary solvent isotope effect k_DO/k_HO = 2.00 (see text).

^c k _rel = relative rate constants for deprotonation compared to value for linear N-acyl glycyl amide as reference. The k_rel values have been statistically corrected for the number of exchangeable protons.

^dInterpolated values from a Brønsted analysis (see text).