Table 1. pK_a,0, δ_H, and δ_L for NMR Indicators.

50% 1-propanol/H2O				50% DMSO/H2O			30% CD3CN/H2O
indicator	pKa,0	δH/ppm	δL/ppm	pKa,0	δH/ppm	δL/ppm	pKa,0	δH/ppm	δL/ppm
2,6-DHBa	1.61 ± 0.29	6.4781	6.3113	1.02 ± 0.19	6.4911	6.3362	1.54 ± 0.40	6.4999	6.3680
1,2,4-triazole	1.80 ± 0.36	9.2221	8.3164b	1.77 ± 0.19	9.1934	8.3621b	2.33 ± 0.41	9.1539	8.3278b
DMGc				2.64 ± 0.21	4.0328	3.5755	2.45 ± 0.42	3.9985	3.6370
salicylic acid				3.33 ± 0.22	7.5679	7.3772
glycolic acid	4.47 ± 0.36	4.1722	3.9171d	4.82 ± 0.30	4.0994	3.7583d	4.43 ± 0.46	4.1716	3.8643d
acetic acid	5.47 ± 0.38	2.0516	1.9160d	5.72 ± 0.31	2.0293	1.8048d	5.46 ± 0.54	2.0583	1.8485d
IM	5.93 ± 0.44	8.7791	7.7155				6.61 ± 0.56	8.6442	7.7254
2MI	6.87 ± 0.47	2.6227	2.3574	6.66 ± 0.35	2.5790	2.3181	7.56 ± 0.59	2.5717	2.3233
4CN	8.54 ± 0.48	7.5160	7.2840	8.29 ± 0.37	7.6617	7.3510	8.44 ± 0.61	7.6370	7.4052
DMG	9.50 ± 0.50	2.9373e	2.2328e	9.45 ± 0.47	3.5870c	2.8685c	9.83 ± 0.69	3.6512c	2.9289c

^apK_a,0, δ_L, and δ_H obtained in the absence of 1,2,4-triazole using eqs 1–4, uncertainty obtained from experiment with 40 mM 1,2,4-triazole.

^bAverage of δ_L determined in solution of triazole (40 mM) and DSS and in acidic range sample.

^cCH₂ resonance of DMG.

^dAverage of acidic and basic range samples in the absence of 2,6-DHB.

^eMethyl resonance of DMG.