posted by Jess .
I know caffeine is more polar than salicylic acid but how would I explain that given their respective structures?
I know for smaller molecules you would figure out the polarity of individual bonds and the molecule's geometry but I can't figure out how to transfer this to more complex molecules.
The only way I know is to look at the polar groups. For SA you cn see the OH and the COOH. You know those are polar groups and you can look up the Ka values. For caffeine the Kb for caffeine (from the N) can be found. Those values can givae you a feel but I don't know of a fool proof method. Some other tutor may.
Sorry but what do Ka/Kb values tell me?