Table 1. S–N bond lengths calculated using CPCM (Å), experimental pK_a values and predictions made using the equation for the S–N/CPCM bond length versus pK_a value for 30 analogues: pK_a = 123.194 × r(S–N) – 202.904. Values and prediction errors obtained using the Marvin program are also shown, with MAE, σ and RMSEP reported for the lowest prediction errors.

ID	Drug	r(S–N)	Exp. pKa	AIBL-pKa	AE	Marvin	AE
TSU-1	Chlorpropamide	1.68513	4.75 (ref. 53)	4.69	0.06	4.31	0.44
TSU-2	Carbutamide	1.69367	5.79 (ref. 54)	5.75	0.04	4.35	1.44
TSU-3	Acetohexamide	1.68266	4.31 (ref. 54)	4.39	0.08	3.33	0.98
TSU-4	Glibenclamide	1.68980	5.22 (ref. 55)/5.30 (ref.56)/6.80 (ref. 56)	5.27	0.05/0.03/1.53	4.32	0.90/0.98/2.48
TSU-5	Glipizide	1.68822	5.21 a /5.90 (ref.57)	5.07	0.14/0.83	4.32	0.89/1.58
TSU-6	Glimepiride	1.69235	5.32 a /7.26 (ref. 52)/8.03 (ref. 52)	5.58	0.26/1.68/2.45	4.32	1.00/2.94/3.71
	MAE				0.10		0.94
	σ				0.09		0.31
	RMSEP				0.13		0.98

^apK_a value measured in this work. All bond lengths for compounds TSU-1 to TSU-6 are given in Table S16 in the ESI.