[kri]

I found out the pka values of ranitidine are 2.7 and 8.2. Not too sure which ionisable groups constitute to those 2 pka values. Wonder if dimethylamino group gives the pka value 8.2 and furan ring  gives the pka value of 2.7? Is 2.7 the unionised form and 8.2 the ionised form?

Please help me. Thanks.

[Dan]

Start by identifying the two most acidic protons in the structure