Is Acetone Polar or Nonpolar? (And Why?)

Acetone (C3H6O) is a POLAR molecule.

But why? 

And how can you say that acetone is a polar molecule?

Want to know the reason?
Let’s dive into it!

Acetone (C3H6O) is a POLAR molecule because the Oxygen (O) present in the molecule is more electronegative, which causes the partial positive (ẟ+) and partial negative (ẟ-) charge to appear on the molecule. These ẟ+ and ẟ- charges are responsible to make the entire acetone molecule polar.

Let me explain this in detail with the help of acetone lewis structure and its 3D geometry.

Why is Acetone a Polar molecule? (Explained in 2 Steps)

Acetone (C3H6O) is a polar molecule because it has poles of partial positive charge (ẟ+) and partial negative charge (ẟ-) on it.

Let me explain this to you in 2 steps!

Step #1: Draw the lewis structure

Here is a skeleton of C3H6O lewis structure and it contains C-H bonds, C-C bonds and C-O bond.

(Note: If you want to know the steps of drawing the acetone lewis dot structure, then visit this article: Acetone lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the C3H6O molecule has C-H bonds, C-C bonds and C=O bond.

Now in the next step we have to check whether these bonds are polar or nonpolar.

And we also have to check the molecular geometry of C3H6O.

Step #2: Check the bond polarity and molecular geometry

The chemical bonds can be either nonpolar, polar or ionic depending on the difference of the electronegativity values (ΔEN) between the two atoms.

Have a look at the above image.

• If the electronegativity difference (ΔEN) is less than 0.4, then the bond is nonpolar covalent bond.
• If the electronegativity difference (ΔEN) is between 0.4 to 1.7, then the bond is polar covalent bond. 
• If the electronegativity difference (ΔEN) is greater than 1.7, then the bond is an ionic bond. ^{[1] [2] [3] [4] [5]}

Now let’s come to the example of acetone (C3H6O) molecule. It has C-H bonds, C-C bonds and C=O bond.

You can see the electronegativity values of Carbon (C), Hydrogen (H) and Oxygen (O) atoms from the periodic table given below.

From the above image;

• Electronegativity of Carbon (C) = 2.55 ^[6]
• Electronegativity of Hydrogen (H) = 2.2 ^[7]
• Electronegativity of Oxygen (O) = 3.44 ^[8]

Now let’s see the polarity of each bond.

For C-H bond;
The electronegativity difference (ΔEN) = 2.55 – 2.2 = 0.35 
This value is less than 0.4, which indicates that the bond between Carbon (C) and Hydrogen (H) is nonpolar.
Hence, each C-H bond is a nonpolar covalent bond.

For C-C bond;
The electronegativity difference (ΔEN) = 2.55 – 2.55 = 0 
This value is less than 0.4, which indicates that the Carbon-Carbon is nonpolar.
Hence, each C-C bond is a nonpolar covalent bond.

For C=O bond;
The electronegativity difference (ΔEN) = 3.44 – 2.55 = 0.89
This value lies between 0.4 to 1.7, which indicates that the bond between Carbon (C) and Oxygen (O) is polar.
Hence, the C=O bond is a polar covalent bond.

You can see in the above image that because of higher electronegativity of Oxygen atom, the partial positive charge (ẟ+) appears on the Carbon atom (C) as well as Hydrogen atoms (H) and partial negative charge (ẟ-) appears on the Oxygen atom (O).

From this, you can easily get the idea that the acetone (C3H6O) molecule is a polar molecule.

But let’s also see its 3D molecular geometry for better understanding.

Have a look at this 3D structure of C3H6O. The more electronegative oxygen atom (O) has a tendency to pull the shared electron pair towards itself, which results in partial positive charge on carbon atom (C) & hydrogen atom (H) and partial negative charge on oxygen atom (O).

Because of this, there are positive and negative poles of charges on the overall molecule of C3H6O.

Hence, the C3H6O molecule is a polar molecule.

I hope you have understood the reason behind the polar nature of C3H6O molecule.

See the polarity of other molecules to make your concepts clear:
Is BrF3 Polar or Nonpolar?
Is IF5 Polar or Nonpolar?
Is O3 Polar or Nonpolar?
Is NO3- Polar or Nonpolar?
Is CH2F2 Polar or Nonpolar?