How do I know which aromatic group is more polar?
Polarity basically describes the charge distribution in a compound. Each atom has an electronegativity. If two atoms with differing electronegativities are bound to one another, then the bond is polar. However, if two identical polar bonds are opposite one another, then they cancel one another out. So if I had the CH4 with carbon in the center and the four H at the four corners, each bond would be polar. However, the entire molecule would be non-polar because all the Hs cancel one another out. However, if I had CH3Cl, then the molecule would be polar because the C-Cl bond would be opposite the C-H bond and they would not cancel. In your example, Para puts the bromine and nitro groups opposite one another so they partially cancel one another. Meta, they are two carbons apart (on carbon 1 and 3) so they kind of cancel. Ortho they are right next to each other and so they don’t cancel at all and this molecule is the most polar. Hope it helps!
