4.27     Draw diagrams showing the formation of a double bond and a triple bond between carbon atoms in C_{2}H_{4}  and C_{2}H_{2} molecules.

Answers (1)
D Divya Prakash Singh

We have the electronic configuration of C-atom in the excited state is:

C= 1s^22s^12p_{x}^12p_{y}^12p_{z}^1

Formation of an ethane molecule (C_{2}H_{4}) by overlapping of a sp^2hybridized orbital of another carbon atom, thereby forming a C-C sigma bond.

The remaining two sp^2 orbitals of each carbon atom from a sp^2-s sigma bond with two hydrogen atoms. The unhybridized orbital of one carbon atom undergoes sidewise overlap with the orbital of a similar kind present on another carbon atom to form a weak n-bond.

c2h4 ethene

Formation of C_{2}H_{2} molecule, each C-atom is sp hybridized with two 2p-orbitals in an unhybridized state.

One sp hybrid orbital of one carbon atom overlaps axially with sp hybrid orbital of the other carbon atom to form C–C sigma bond, while the other hybridised orbital of each carbon atom overlaps axially with the half-filled s orbital of hydrogen atoms forming σ bonds

Each of the two unhybridised p orbitals of both the carbon atoms overlaps sidewise to form two π bonds between the carbon atoms. So the triple bond between the two carbon atoms is made up of one sigma and two pi bonds as shown in Fig

 

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