Heres the question: http://img266.imageshack.us/img266/5071/sar2.png [Broken] I have no idea how to answer either of these questions. I know that the methyl group attached to the carboxyl groups alpha carbon will decrease the acidity due to electron donating properties. It doesn't look like the carbonyl group is conjugated with the aromatic rings so I don't think they will increase the acidity too much. Thats all I can say about it though, I have no idea how to estimate the pKa. I'm also confused about question b. I suppose one advantage is that the salt is not acidic.