Question

The length of the carbon-carbon single bond of the compounds

I) $C{H}_2=CH-C\equiv CH$
II) $CH\equiv C-C\equiv CH$
III) $C{H}_3-CH=C{H}_2$
IV) $C{H}_2=CH-CH=C{H}_2$

is expected to decrease in the order :

• A. III > II > I > IV
• B. I > III > II > IV
• C. III > IV > I > II
• D. II > IV > I > III

Answer 1

The correct option is C III > IV > I > II

The decrease in $C-C\sigma$ bond length as $C$ hybridization changes from $s{p}^3$ to $s{p}^2$ to $sp$ reflects the decrease in the bond length. The shortening of all these bonds is a consequence of the adjacent double and triple bonds. The the carbon-carbon single bond of the alkyne is shorter than alkene and those of alkane. The order of bond length is $II<I<IV<III$