. Author manuscript; available in PMC: 2013 Jun 25.

Published in final edited form as: Chempluschem. 2012 Mar 13;77(5):370–378. doi: 10.1002/cplu.201100072

Table 1. The hydroxyl pKa values of coumarins 1-5.

Coumarins	pKa_(OH-7)	pKa_(OH-6)	pKa_(OH-8)
3,4-cyclohexenoesculetin 1	11.84	8.74	---
7,8-dihydroxy-3,4-cyclohexenocoumarin 2	11.48	---	7.95
6,7-dihydroxy-4-methylcoumarin 3 ^*	10.28	8.52	---
7,8-dihydroxy-4-methylcoumarin 4 ^*	10.35	---	8.00
7,8-dihydroxy-6-methoxycoumarin 5	10.49	---	7.22

Values from ^[36], while others were calculated using Advanced Chemistry Development Software (www.acdlabs.com).