MOLECULAR POLARITY Covalent Compounds  Elmhurst College Electrostatic Potential Organic Functional Groups Functional Gps vs. Boiling Pt.  Chemistry Department Simple Inorganics Organic Chain Length  Virtual ChemBook

Polarity of Organic Compounds Principles of Polarity: The greater the electronegativity difference between atoms in a bond, the more polar the bond. Partial negative charges are found on the most electronegative atoms, the others are partially positive. The molecular electrostatic potential is the potential energy of a proton at a particular location near a molecule. Negative electrostatic potential corresponds to: partial negative charges (colored in shades of red). Positive electrostatic potential corresponds to: partial positive charges (colored in shades of blue).

Comments on the Electrostatic Potential graphics below: As you view the graphics, the idea is to develop the concept of polarity in a visual manner. The more areas of red and blue that you see, the more polar is the compound and the functional group in the compound. Look at the amide, and acid. The more areas of gray and lighter shades of red and blue, the more non-polar properties are being depicted. Look at the amine, ether, and alkane. A strong exception based on the above statements is that the ester should have a much higher ranking than it does based upon the boiling point information. Other factors may also be important.

Functional Group Ranking by Boiling Points
R = any number carbons in a hydrocarbon chain *CHIME plug-in required to view these images.
Functional Group Name	Boiling Point	Polar Rank (most to least)	Structure Name	Name Chime*
Amide	222o	1		ethanamide Chime in new window
Acid	118o	2		ethanoic acid or acetic acid Chime in new window
Alcohol	117o	3	CH3CH2CH2OH	propanol Chime in new window
Ketone	56o	4, 5		propanone or acetone Chime in new window
Aldehyde	49o	4, 5		propanal Chime in new window
Amine	49o	6	CH3CH2CH2NH2	propylamine Chime in new window
Ester	32o	7		methyl ethanoate Chime in new window
Ether	11o	8	CH3-O-CH2CH3	methyl ethyl ether Chime in new window
Alkane	-42o	9	CH3CH2CH3	propane Chime in new window