Question

In the compound $C{H}_3-CH=CH-C{H}_2-C\equiv CH$, the hybridisation of C₁, C₃ and C₅ bonds respectively is

• A. $s{p}^3,spands{p}^2$
• B. $s{p}^3,s{p}^{3}andsp$
• C. $sp,s{p}^{3}ands{p}^2$
• D. $s{p}^2,spands{p}^3$

Answer 1

The correct option is C $sp,s{p}^{3}ands{p}^2$

Short version: $C_1$ is $sp$ hybridised, $C_3$ is $s{p}_3$ hybridised and $C_5$ is $s{p}_2$ hybridised.

Long version:
In the case of hybridisation of carbon, the easiest way is to look at the number of atoms it is bonded with or the presence of double or triple bonds

If the carbon is bonded to 4 other atoms, it is $s{p}_3$ hybridised since $s{p}_3$ hybridisation gives rise to 4 hybrid orbitals of equal energy levels which can participate in bonding. This allows carbon to form 4 σ bonds.

If the carbon is bonded to 3 other atoms, it is $s{p}_2$ hybridised giving rise to 3 hybrid orbitals and one p-orbital. This allows the formation of 3 σ bonds and 2 π bonds i.e. one double bond and 2 single bonds.

The reasoning for $sp$ hybridisation similar. Just look for a triple bond.