How do I rank the following molecules from highest to lowest in molecular polarity?

CH3-CH2-CH2-CH3
HO - CH2 - CH2 - CH2 - CH3
CH3CH2 - O - CH2CH3

Question

How do I rank the following molecules from highest to lowest in molecular polarity? 

CH3-CH2-CH2-CH3
HO - CH2 - CH2 - CH2 - CH3 
CH3CH2 - O - CH2CH3

anonymous · Answer

First of all there is no net dipole in Butane as it is symmetrical .
Now you have to see the other two compounds. O is sp3 hybrid and has V shape. |dw:1329456942617:dw| If you see the alcohol the O has a hydrogen bonded to it which is highly electropositive and hence the bond exists as a partial positive on H and a negative on O.|dw:1329457003867:dw| The carbon chain is a +I group and hence it too would have polarity. In the ether there are 2 carbons on either sides and hence here polarity would be due to +I effect. Now here the polarity of O H bonf is very high and hence the alcohol would have a higher dipole than the ether. So the order of polarity would be 2>3>1.