Writing Lewis Structures a step by step approach: Acrylonitrile C3H3N –#33

A simple procedure for writing Lewis structures is given in a previous article entitled “Lewis Structures and the Octet Rule”. Relevant worked examples were given in the following articles: Examples #1, #2, #3 , #4, #5, #6,  #7,  #8, #9, #10, #11, #12, #13, #14,  #15, #16, #17, #18, #19, #20, #21, #22,  #23,  #24, #25, #26, #27, #28, #29, #30, #31 and #32.

Let us consider the case of  acrylonitrile, C₃H₃N:

 

Step 1: Connect the atoms with single bonds.

Fig. 1: Connect the atoms of  C₃H₃N  with single bonds

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

Where n in this case is 4 since C₃H₃N  consists of 7 atoms but 3 of them are H atoms.

Where V = 3*4 + 3*1 + 5  = 20

Therefore, P = 6n + 2 – V = 6 *4 + 2 – 20 = 6    So, there are either i) 3 double bonds or ii)  1 triple and 1 double bond.

The structure in Figure 1 cannot have 3 adjacent double bonds because the middle carbon would have 5 bonds.

The only possibility is 1 triple and 1 double bond and the only possible arrangement is shown in Steps 3 and 4: 

 Step 3 & 4: A draw of the Lewis structure of  acrylonitrile   C₃H₃N  is as follows:

Fig 2: Lewis dot structures of acrylonitrile. Structure #1 is the major contributor to the hybrid since there is an octet of electrons around each atom and there is no charge separation.

Structure #1 is the major contributor to the hybrid - the most stable Lewis resonance structure - since there is an octet of electrons around each atom and there is no charge separation.