Acetic acid (CH3COOH | Ethanoic acid) Lewis Structure and Steps of Drawing

Acetic acid (CH3COOH) contains oxygen, carbon and hydrogen atoms. Lewis structure of acetic acid (CH3COOH) contains 3 C-H bonds, 1 C=O bond, 1 C-O bond, 1 O-H bond and 1 C-C bond. Each oxygen atom has 2 two lone pairs. We will learn how to draw lewis structure of CH3COOH step by step in this tutorial.

CH3COOH lewis structure

CH3COOH acetic acid lewis structure

Figure of CH3COOH lewis structure is given above and you can see how atoms are made with other atoms. Also, there are no charges on atoms and acetic acid also does not have an overall charge.

Steps of drawing lewis structure of CH3COOH

There are several steps to draw the lewis structure of CH3COOH. Each step is explained in detail in this tutorial.

  1. Find total number of electrons of the valance shells of hydrogen, oxygen atoms and carbon atom
  2. Total electrons pairs as lone pairs and bonds
  3. Center atom selection
  4. Mark lone pairs on atoms
  5. Mark charges on atoms if there are charges.
  6. Check the stability and minimize charges on atoms by converting lone pairs to bonds to obtain best lewis structure.
steps of drawing CH3COOH acetic acid lewis structure

Total number of electrons of the valance shells of CH3COOH

There are 3 elements in acetic acid molecule; hydrogen, carbon and oxygen. Hydrogen is a group IA element and has only one electron in its last shell (valence shell). Oxygen is a group VIA element in the periodic table and contains six electrons in its last shell. Carbon atom has 4 electrons in its last shell because it is IV group element. Now we know how many electrons are includes in valence shells of atoms.

  • valence electrons given by hydrogen atoms = 1 * 4 = 4
  • valence electrons given by carbon atom = 4 * 2 = 8
  • valence electrons given by oxygen atom = 6 * 2 = 12

  • Total valence electrons = 4 + 8 + 12 = 24

Total valence electrons pairs

Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells

Total electron pairs are determined by dividing the number total valence electrons by two. For, CH3COOH, Total pairs of electrons are 12 (24/2) in their valence shells.

Center atom and basic sketch of CH3COOH

To be the center atom, ability of having greater valance and being most electropositive element in the molecule are important facts. These are not essential. But those two facts play a major role in selecting center atom of a molecule.

However, CH3COOH is not a simple molecule with 3, 4 atoms, there are several center atoms in CH3COOH molecule. We know that carbon atom has the highest chance to be center atoms than hydrogen and oxygen atoms because carbon has the highest valence (4) from those 3 elements.

Basic sketch of CH3COOH is given below.

CH3COOOH basic sketch

Lone pairs on atoms

After deciding the center atom and sketch of CH3COOH molecule, we start to mark lone pairs on atoms. Remember that, there are total of 12 electron pairs to mark on atoms as bonds and lone pairs.

  • There are already 7 bonds in the above drawn sketch. Now only 5 (12-7) electron pairs are remaining to mark on atoms.
  • Usually, those remaining electron pairs should be started to mark on outside atoms. But, hydrogen atoms cannot keep more than two electron in its last shell and there is no possibility mark lone pairs on hydrogen atoms.
  • Therefore, then mark those electrons pairs on oxygen atoms; one oxygen atom will take 3 lone pairs and other oxygen atom will take 2 lone pairs. Now all 5 lone pairs were marked and no more lone pairs to mark on carbon atoms.
mark lone pairs on CH3COOh acetic acid structure

Mark charges on atoms

There are charges on one oxygen atom and one carbon atom.

Check the stability and minimize charges on atoms by converting lone pairs to bonds

Because there is charges on atoms, no need to check that whether charges can be reduced or not. Reducing charges on atoms as a step will give the stable structure. As below, we can reduce charges by converting a lone pair on charged oxygen atoms to a bond.

reduce charges on atoms in CH3COOH