How can you determine that Caffeine in more polar than Acetaminophen and Acetaminophen is more polar than Aspirin?

I understand that Caffeine has very electronegative O and N atoms causing a slight pull toward there molecules due to their negative charge and the H and C are more positive.

Acetaminophen has an OH group, NH, and a double bonded O, I know that O and N are more EN than H.

Aspirin has an OH group, 2 double bonded O's and a single bonded O. O is more EN than H.

What I don't understand is how you can tell that one is more polar than the other.

Question

How can you determine that Caffeine in more polar than Acetaminophen and Acetaminophen is more polar than Aspirin? 

I understand that Caffeine has very electronegative O and N atoms causing a slight pull toward there molecules due to their negative charge and the H and C are more positive. 

Acetaminophen has an OH group, NH, and a double bonded O, I know that O and N are more EN than H.

Aspirin has an OH group, 2 double bonded O's and a single bonded O. O is more EN than H.  

What I don't understand is how you can tell that one is more polar than the other.

koikkara · Answer

Rank polarity of Aspirin, ibuprofen, acetaminophen, caffeine, and phenacetin from most to least polar. Explain. Caffeine > Acetaminophen > phenacetin > Aspirin > Ibuprofen

Aspirin is more polar than ibuprofen - more H bond acceptors and donators. Acetaminophen is more polar than phenacetin - it has an OH that can H bond. Caffeine is the most polar @Summersnow8 Was your doubt cleared ?