Question

How many sigma and pi bonds are present in tetracyanoethylene?
A. Nine $$\sigma $$ and nine $$\Pi $$
B. Five $$\Pi $$ and nine $$\sigma $$
C. Nine $$\sigma $$and seven $$\Pi $$
D. Eight $$\sigma $$and eight $$\Pi $$

Answer 1

Hint: The pi bonds are defined as the bonds which are formed by the side wise overlapping of the atom orbital. The pi bonds are formed after the sigma bonding takes place. The sigma bond is formed by the axial overlapping of the atomic orbital.

Complete step by step answer:
The chemical; structure of the tetracyanoethylene is drawn below. The structure has 5 carbon atoms and four nitrogen atoms. There are three triple bonds, four single bonds and one double bond in the structure. As I told you earlier that pi bond is formed after sigma bond so the double bond will have one pi bond and triple bond will have two pi bonds.

So after seeing the structure we get to know that the central carbon atoms attached to the side carbon are bonded by a single bond. So all single bonds are sigma bonds. So here singly bonded sigma bonds are 4. The double bonded sigma bond in this structure is 1 which is the central C-C bond. The triple bonded sigma bond in this structure is 4 which are carbon nitrogen bonds. So the total sigma bonds are 9 $$\sigma $$bonds. So now the pi bond in double bonded atoms is 1 that is the central C-C bond. The other 2 pi bonds in each triple bonded carbon nitrogen bonds are in total 8. So the total pi bonds are 9.

so the correct option for the question is option A.




Note: sigma bonds are more stronger than pi bonds because they hold the atoms rigidly in it. They also overlap the orbital directly. Due to which the electron density gets more concentrated between the two nuclei.