Table 1. Summary of Second-Order Rate Constants for C(3)-H/D Exchange (k_DO) for 7a–c,k (n = 1); 8a–c,k (n = 2); 9a–c, 9k (n = 3) and Calculated C(3)-H pK_a Values.

triazolium salt	n	R =	kDO (M–1 s–1)a	kDOreld	pKae
7a	1	4-OMe	4.55 (±0.36) × 107	2.26	17.7
7a			4.20 (±0.23) × 107b	2.09	17.8
8a	2		2.11 (±0.18) × 107	1.05	17.9
9a	3		2.01 (±0.20) × 107	1	18.0
7b	1	H	6.99 (±0.18) × 107	2.12	17.5
7b			6.82 (±0.13) × 107b	2.07	17.5
8b	2		3.43 (±0.15) × 107	1.04	17.8
9b	3		3.29 (±0.15) × 107	1	17.8
7c	1	4-F	8.97 (±0.27) × 107	2.04	17.4
7c			8.66 (±0.11) × 107b	1.97	17.4
8c	2		5.00 (±0.31) × 107	1.14	17.7
9c	3		4.39 (±0.16) × 107	1	17.7
7k	1	–F5	3.52 (±0.37) × 108c	0.87	16.8
7k			6.82 (±0.25) × 108b,c	1.69	16.5
8k	2		4.16 (±0.19) × 108	1.03	16.7
9k	3		4.04 (±0.19) × 108	1	16.7

^aThis work.

^bValues of k_DO (M^–1 s^–1) obtained previously.

^cThe error quoted for 7k is that obtained based on the overall fit to eq 3 for all of the data. The larger variance from our previous value for 7k is due to the unavoidably small number of data points in the region of unit slope. The k_DO value obtained previously is deemed more reliable owing to the lower overall error in fitting to eq 3 as a result of having a greater number of data points.

^dCalculated as k_DO^rel = k_DOⁿ/k_DOⁿ⁼³.

^epK_a values calculated using experimental k_DO values (vide infra).