Question

$H-C\equiv C\stackrel{a}{-}C\equiv C\stackrel{b}{-}C{H}_3$
Compare the bond length $a$ and $b$.

• A. $a=b$
• B. $a>b$
• C. $b>a$
• D. $a>>>b$

Answer 1

Answer: (C)

$b>a$

Here bond ${}^{\prime }{b}^{\prime }$ is formed between a $s{p}^3$ hybridized carbon atom and a $sp$ hybridized carbon atom. While bond ${}^{\prime }{a}^{\prime }$ is formed between two $sp$ hybridized carbon atoms. Since $sp$ hybridized atoms have greater $s$ character and hence shorter orbitals compared to $s{p}^3$ hybridized atoms, therefore, bond ${}^{\prime }{a}^{\prime }$ is shorter than ${}^{\prime }{b}^{\prime }$.