Hydrocarbons 2 Question 56
60. An alkene $(A) \mathrm{C}{16} \mathrm{H}{16}$ on ozonolysis gives only one product $(B) \mathrm{C}{8} \mathrm{H}{8} \mathrm{O}$. Compound $(B)$ on reaction with $\mathrm{NaOH} / \mathrm{I}{2}$ yields sodium benzoate. Compound $(B)$ reacts with $\mathrm{KOH} / \mathrm{NH}{2} \mathrm{NH}{2}$ yielding a hydrocarbon $(C) \mathrm{C}{8} \mathrm{H}{10}$. Write the structures of compounds $(B)$ and $(C)$. Based on this information two isomeric structures can be proposed for alkene $(A)$. Write their structures and identify the isomer which on catalytic hydrogenation $\left(\mathrm{H}{2} / \mathrm{Pd}-C\right)$ gives a racemic mixture.
(2001)
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Solution:
- $B+\mathrm{NaOH}+\mathrm{I}{2} \longrightarrow \mathrm{C}{6} \mathrm{H}_{5}-\mathrm{COONa}$ (Iodoform reaction)
$\therefore B$ is $\mathrm{C}{6} \mathrm{H}{5}-\stackrel{\mathrm{O}}{\mathrm{C}}-\mathrm{CH}_{3}$
$B+\mathrm{N}{2} \mathrm{H}{4} \xrightarrow{\mathrm{KOH}}$ Hydrocarbon $(C)$ “Wolff-Kishner Reduction”
$\therefore C$ is $\mathrm{C}{6} \mathrm{H}{5}-\mathrm{CH}{2}-\mathrm{CH}{3}$
Hence, $A$ can be one of the following :
I on catalytic hydrogenation, would give meso compound while II on catalytic hydrogenation, would produce racemic mixtures.
