Chemical Bonding and Molecular Structure - Result Question 74
####76. The cylindrical shape of an alkyne is due to the fact that it has
(a) three sigma $C-C$ bonds
[1997]
(b) two sigma $C-C$ and one ’ $\pi$ ’ $C-C$ bond
(c) three ’ $\pi$ ’ $C-C$ bonds
(d) one sigma $C-C$ and two ’ $\pi$ ’ $C-C$ bonds
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Solution:
- (d) In alkynes the hybridisation is $s p$ i.e each carbon atom undergoes $s p$ hybridisation to form two $s p$-hybrid orbitals. The two $2 p$-orbitals remain unhybridised. Hybrid orbitals form one sigma and two unhybridised orbitals form $\pi$ bonds.
Hence two $\pi$ bond and one sigma bond between $C-C$ lead to cylindrical shape.
