Lewis structure of CH3COOH

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The Lewis structure of CH₃COOH contains one double bond and six single bonds, with two carbons in the center. The left carbon is attached with three hydrogens, and right carbon is attached with two oxygens and one hydrogen. There are two lone pairs on each oxygen atom, and carbon atom and hydrogen atom do not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of CH₃COOH:

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… carbon is a group 14 element, hydrogen is a group 1 element, and oxygen is a group 16 element. Hence, carbon has four valence electrons, hydrogen has one valence electron, and oxygen has six valence electrons.

Now CH₃COOH has two carbon atoms, four hydrogen atoms, and two oxygen atoms.

So the total number of valence electrons = (valence electrons of carbon atom × 2) + (valence electrons of hydrogen atom × 4) + (valence electrons of oxygen atom × 2)

Therefore, the total number of valence electrons = 8 + 4 + 12 = 24

• Now decide the central atom

We can not assume hydrogen as the central atom, because the central atom is bonded with at least two other atoms. And hydrogen has only one electron in its last shell, so it can not make more than one bond.

Therefore, choose the central atom from carbon and oxygen.

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for carbon and oxygen as follows:

Electronegativity value of carbon = 2.55
Electronegativity value of oxygen = 3.44

Obviously, carbon is less electronegative than oxygen. Hence, assume that right carbon is the central atom (as there are two carbons).

So now, put two carbons in the center and two oxygens and four hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of CH₃COOH something like this:

Also read: How to draw Lewis structure of ClO^– (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since two carbons are surrounded by two oxygens and four hydrogens, use fourteen electrons to show seven chemical bonds as follows:

#3 Mark lone pairs

As calculated earlier, we have a total of 24 valence electrons. And in the above structure, we have already used fourteen valence electrons. Hence, ten valence electrons are remaining.

Two valence electrons represent one lone pair. So ten valence electrons = five lone pairs.

Note that both (carbon and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are hydrogens, oxygens, and left carbon. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.

So top oxygen will get three lone pairs, and right oxygen will get two lone pairs. And the left carbon and central atom (right carbon) will not get any lone pair, because all five lone pairs are used.

Now draw the Lewis structure of CH₃COOH something like this:

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (right carbon) doesn’t form an octet.

So in the next step, we have to complete the octet on the central atom.

Also read: How to draw Lewis structure of Cl₂O (4 steps)

#4 Complete octet on central atom

Remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Now right carbon already has six valence electrons. Hence, right carbon needs two more valence electrons to complete its octet.

Which means that we have to convert one lone pair. But the question is, which lone pair should we convert to get the best Lewis structure?

There are two possible ways we can convert lone pair: 

1) Convert one lone pair from the top oxygen atom.
2) Convert one lone pair from the right oxygen atom.

In order to get the best Lewis structure, we have to make the formal charges on atoms closer to zero. And we can do so by choosing the 1).

So convert one lone pair from the top oxygen atom to make a new bond with the right carbon atom. And then, the Lewis structure of CH₃COOH looks something like this:

In the above structure, you can see that the octet is completed on the central atom (right carbon), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of ClO₄^– (5 steps)

#5 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

Collect the data from the above structure and then, write it down below as follows:

• For each carbon atom

Valence electrons = 4
Nonbonding electrons = 0
Bonding electrons = 8

Formal charge = 4 – 0 – ½ (8) = 0

• For each hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

• For each oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of CH₃COOH looks something like this:

In the above structure, you can see that the formal charges of all atoms are zero. Therefore, this is the stable Lewis structure of CH₃COOH.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Related

• Lewis structure of ClO^–
• Lewis structure of Cl₂O
• Lewis structure of ClO₄^–
• Lewis structure of CBr₄
• Lewis structure of SeO₂

External video

• CH3COOH Lewis Structure (Acetic acid) – YouTube • Wayne Breslyn

External links

• CH3COOH lewis structure, molecular geometry, polarity, hybridization – Topblogtenz
• Ethanoic acid) Lewis Structure and Steps of Drawing – Chemistry School
• Drawing the Lewis Structure for CH3COOH (Acetic Acid) – The Geoexchange
• What is the Lewis Dot Structure of CH3COOH (Acetic Acid)? – Quora
• Draw the Lewis structure for CH3COOH and determine the geometry, orbital hybridization, and bond angles around the second carbon – Homework.Study.com
• Lewis structure of acetic acid CH3COOH – Chemistry Online
• CH3COOH (Acetic acid) Lewis Structure in 6 Steps – Pediabay
• Lewis Dot of Acetic Acid (Ethanoic Acid) CH3COOH – Kent’s Chemistry
• What is lewis structure for ch3co2h – Brainly
• The Lewis Dot Structure for Acetic Acid (CH3COOH) – MakeTheBrainHappy
• Determine the (1) number of valence electrons, the (2) Lewis Structure for the acetic acid (CH3COOH) and (3) give the hybridization of each carbon within the molecule – Numerade
• What is the geometry around each of the three central atoms in the CH3COOH molecule? – Socratic
• Draw the Lewis structure of acetic acid (CH3COOH) and methyl amine (CH3NH2) – Bartleby
• Does CH3COOH have resonance? – Reddit