Acetic acid (CH3COOH) lewis structure, molecular structure, hybridization, polarity

CH3COOH lewis structure is made up of two carbon (C), two oxygen (O), and four hydrogens (H). There are a total of 4 lone pairs, 6 single bonds, and 1 double bond present in the lewis dot structure of CH3COOH.

Lewis structure of CH3COOH is not much difficult to draw as you might think. We only need a good approach to draw the lewis diagram of any molecule, it doesn’t matter whether the molecule simple or complex.

Now we will draw the lewis structure of acetic acid step by step with all possible explanations.

Follow some steps for drawing the lewis dot structure of CH3COOH (Acetic acid)

1. Count total valence electrons in CH3COOH

As we know, Lewis structure or electron dot structure helps us to know, how atoms or valence electrons are arranged in a molecule. So, the first step of drawing the lewis diagram of any molecule is to determine the valence electron present within a molecule.

Valence electrons are the electrons that are present in the outermost shell of the atom. To find the valence electron in the CH3COOH molecule, just look at their periodic group of atoms.

As carbon belongs to the 14th periodic group, oxygen to the 16th, and hydrogen is present in the 1st group of the periodic table. Hence, the valence electron for carbon is 4, for oxygen, it is 6, and for hydrogen, it is 1.

⇒ Total number of the Valence electron in carbon = 4

⇒ Total number of the valence electrons in oxygen = 6

⇒ Total number of the valence electrons in hydrogen = 1

∴ Total number of valence electron available for the lewis structure of CH3COOH = 4(2) + 6(2) + 1(4) = 24 valence electrons         [∴CH3COOH molecule contains two carbon, two oxygen, and 4 hydrogen]

2. Find the least electronegative atom and placed it at center

As less electronegative atoms are more prone to share more electrons with surrounding atoms, hence in lewis’s diagram, the least electronegative atom always holds the place of the central position.

In the CH3COOH molecule, three types of atoms are present – hydrogen, oxygen, and carbon. It should be noted that in the lewis diagram, hydrogen atoms always go outside means they always hold the place of the surrounding position, no matter what the situation is.

This is because hydrogen can only hold two valence electrons in its outermost shells.

From carbon and oxygen, the carbon atom(2.55) is less electronegative than the oxygen atom(3.44), hence carbon holds the place of a central position in the lewis diagram.

Are you wondering how we place these atoms in random positions in the above structure? CH3COOH molecule contains a functional group that is also called the carboxylic group(COOH). This group is always working together in a structure.

A functional group in organic chemistry is a collection of atoms within molecules which bind together to react in predictable ways.

Therefore, in the above structure, the COOH group atoms are placed together whereas hydrogen always goes outside in the lewis diagram.

3. Connect outer atoms to the central atom with a single bond

Here we connect all surrounding atoms with the central atom by a single bond. So, just connect all outside atoms(hydrogen and oxygen) with the central atom(carbon) using a single bond.

Note – COOH functional group will work together.

Now just start to count the valence electron we used in the above structure. A single bond means two valence electrons. In the above structure, 7 single bonds are used for connecting surrounding atoms to the central position.

Hence, 7 × 2 = 14 valence electrons are used in the above structure from a total of 24 valence electrons available for CH3COOH.

∴ (24 – 14) = 10 valence electrons

Therefore, we are left with 10 valence electrons more.

4. Place remaining valence electrons starting from the outer atom first

In this step, we need to complete the octet of outer atoms(hydrogen and oxygen) by putting the remaining valence electron we have. “An octet means having 8 valence electrons in the outermost shell of an atom”.

The hydrogen atom is an exception to the octet rule as it only needs two electrons to fulfill the outermost shell.

As you see in the above structure, we had 10 remaining valence electrons and we put all these on the oxygen outer atom to fulfill their octet, as all hydrogen atoms already have two electrons in their valence shell because of a single bond.

So, each oxygen atom has 8 valence electrons around them and each hydrogen has 2, hence, these atoms completed their octet comfortably.

Let’s move on to the next step to completing the octet of the central atom also.

5. Complete central atom octet and make covalent bond if necessary

As we already completed the octet of the outer atom in the above structure, now we need to complete the central atom(carbon) octet. Carbon needs 8 electrons in its outermost shell to achieve the octet.

If you see the 4th step structure, left side carbon already completed its octet as it is attached to 4 single bonds that share 8 electrons. But the right side carbon has only 3 single bonds that contain 6 electrons.

Hence, we need two more electrons to fulfill the demand for right-side carbon. But we don’t have any remaining valence electrons as we already used them all in the 4th step structure.

So, in these cases, we will convert the lone pair to a covalent bond without violating the octet of any atom.

As you see in the above structure, we convert the one lone pair of oxygen electrons to a covalent bond without violating any octet rule.

By looking at the above structure, we see our right side carbon completed the octet comfortably and the oxygen atom which we have taken one lone pair to convert into the covalent bond also achieved the octet.

Hence, all atoms in the above structure have their octet, so, we can say, we got our lewis structure of CH3COOH.

We completed the lewis structure of acetic acid but we needed to check its stability with the help of the formal charge concept.

6. Check the stability with the help of a formal charge concept

As we know, the lower the formal charges on the atom, the better is the stability of the lewis diagram.

We will calculate the formal charge on the 5th step structure.

⇒ Formal charge formula = (valence electrons – lone pair electrons –  1/2bonded pair electrons)

All hydrogen atoms in the CH3COOH Lewis diagram have zero formal charges, just count the F.C. on carbon and oxygen atoms.

Both carbon atoms have attached to 4 single bonds and zero lone pairs on it, hence, their formal charge will also be the same, so, just count F.C. for one carbon atom

For the carbon atom-

•  Valence electron of carbon = 4
• Lone pair electrons on carbon = 0
•  Bonded pair electrons around carbon = 8 (4 single bond)

∴ F.C. on carbon atom = (4 – 0 – 8/2) = 0

Both oxygen atoms have attached to 2 single bonds and both contain 2 lone pairs. Hence, their formal charge will also same. So, just count F.C. for one oxygen atom.

For oxygen atom-

• Valence electron of oxygen = 6
• Lone pair electrons on oxygen = 4
• Bonded pair electrons around oxygen = 4

∴ F.C. on oxygen atom = (6 – 4 – 4/2) = 0

So, all atoms in the CH3COOH lewis structure have zero formal charge-

Acetic acid (CH3COOH) lewis structure

So, the above lewis structure of Acetic acid (CH3COOH) is the best and most stable as all atoms have a formal charge of zero.

Also check –

• Formal charge calculator
• Lewis structure calculator
• How to draw a lewis structure?

I really hope you enjoyed the procedure of making a lewis diagram with all concepts and possible explanations.