Table 2.

Effect of concentration of NaOH on Impurity E (1) content in the oxidation of pantoprazole sulfide (4) to pantoprazole sulfoxide (5).^a

Entry	NaOH (mmol)	HPLC conversion (%)
		Sulfoxide (5)	Imp A (7)	Sulfide/ Imp B (4)	Imp C (3)	Imp D + F (8,9)	Imp E (1)
1	5	93.88	0.15	0.08	nd	nd	0.31
2	10	95.45	nd	0.13	nd	nd	0.57
3	15	96.12	0.05	0.20	nd	nd	0.64
4	20	96.50	0.03	0.03	nd	0.06	0.84
5	25	97.27	0.24	0.13	nd	0.05	0.94
6	30	95.01	0.05	0.18	nd	nd	0.89

nd : not detected.

^aReaction conditions: 5-(difluoromethoxy)-1H-benzimidazole-2-thiol (3), 10 mmol; NaOCl, 10.5 mmol, assay 9.0%; water, 10 mL at 0–5 °C for 3 h.