Simple Procedure for writing Lewis Structures for Diazomethane CH2N2 -#11

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 and #10. 

Another example  for writing Lewis structures following the above procedure is given bellow:

Let us consider the case of diazomethane (CH₂N₂) . Diazomethane is a yellow, poisonous, potentially explosive compound, which is a gas at room temperature. It is used in the organic chemistry laboratory for the conversion of carboxylic acids to methyl esters and for the conversion of alkenes to cyclopropane.

The resonance structures for CH₂N₂  are as follows:

Step 1: Connect the atoms with single bonds

Fig 1: Connecting the diazomethane atoms CH2N2 with single bonds (step 1 of the method)

Step 2: Calculate the # of electrons in π bonds (multiple bonds) using  formula (1) in the article entitled “Lewis Structures and the Octet Rule”. 

:

Where n in this case is 3 since CH₂N₂  consists of five atoms but two of them are hydrogen.

Where V = (4 + 2 * 1 + 5 + 5 ) = 16   

Therefore, P = 6n + 2 – V = 6 * 3 + 2 – 16 = 4    There are 4 π electrons in CH₂N_2.

Therefore, 2 double bonds or 1 triple bond must be added to the structure of Step 1.

Step 3 & 4: The Lewis structures for CH₂N₂ are as follows:

Figure 2: Lewis structures for CH₂N_2.  Delocalization of the carbon electron pair in structure 2 gives structure 3 which is more plausible since the positive charge is on the carbon atom which is more electropositive than N.

                                                                                   Figure 3: Diazomethane ESP structure