Drawing Lewis Structures: An Easy Method - Methyl acetate CH3COOCH3 – #32

A simple procedure for writing Lewis structures is given in a previous article entitled “Lewis Structures and the Octet Rule”. 

Several worked examples relevant to this procedure were given in previous posts please see the Sitemap - Table of Contents (Lewis Electron Dot Structures).

Let us consider the case of  methyl acetate, CH₃COOCH₃ 

Methyl acetate is a flammable liquid with a characteristic pleasant smell reminiscent of some glues and nail polish removers. It is used as a weakly polar and lipophilic solvent. Because of  its fast evaporation rate is useful in applications where fast solvent release and quick-dry to touch time is required. Methyl acetate is the active solvent for several resins.  

Step 1: Connect the atoms of CH₃COOCH₃ with single bonds

Fig. 1: Connecting the atoms of  CH3COOCH3  with single bonds

 Step 2: Calculate the # of electrons in π bonds (multiple bonds) using  formula (1): 

Where n in this case is 5 since CH₃COOCH₃ consists of 11 atoms but 6 of them are H atoms.

Where V = 4 + 3*1 + 4 + 6 + 6 + 4 +3*1   = 30

Therefore, P = 6n + 2 – V = 6 *5 + 2 – 30 = 2   So there is one double bond and that means the structure in Step 1  has one double bond.

Step 3 & 4: The Lewis structure of CH₃COOCH₃ is as follows:

Fig. 2: Lewis electron dot structures for methyl acetate CH₃COOCH₃. 

Lewis electron dot structure #1 is the major contributor to the hybrid since there are 8 electrons around each atom and there is no charge separation (extra stability). Structure #2 is the least plausible contributor because there is charge separation and positive charge  on an electronegative atom (O atom) (unstable). Structure #3  is a  minor contributor since there is charge separation but the positive charge is on the most electropositive atom (C atom) comparing to the others connected.