Question

what will increase the polarity of an organic molecule to a greater degree-a halogen or an oxygen atom and why?

Answer 1

Bond polarity is directly related to electronegativity difference. The greater the difference in electronegativity the more polar the bond.

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. The Pauling scale is the most commonly used. Fluorine (the most electronegative element) is given a value of 4.0

Covalent bonds formed from two different elements will always have some bond polarization. The degree of bond polarization can be estimated from how far apart the two elements are on the periodic table. The atom closer to fluorine in the periodic table will bear the partial negative charge. Conversely, the atom further from fluorine will bear the partial positive charge.

C-O or C=O --> strong polarization (∂+ on carbon and ∂- on oxygen)

C-X (X=F, Cl, Br, I) --> strong polarization (∂+ on carbon and ∂- on halogen)

a halogen has stronger polarizability then oxygen