Identify the alkyne in the following sequence of reactions,

Identify the alkyne in the following sequence of reactions,

1. $\mathrm{H}_3 \mathrm{C}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_3$
2. $\mathrm{H}_3 \mathrm{C}-\mathrm{CH}_2-\mathrm{C} \equiv \mathrm{CH}$
3. $\mathrm{H}_2 \mathrm{C}=\mathrm{CH}-\mathrm{C} \equiv \mathrm{CH}$
4. $\mathrm{HC} \equiv \mathrm{C}-\mathrm{CH}_2-\mathrm{C} \equiv \mathrm{CH}$

Solution

In Wacker process, alkene is oxidised into aldehyde.
Since on ozonolysis, only alkenes produce aldehydes, ' $A$ ' must be an alkene. To decide the structure of alkene that undergoes ozonolysis, bring the products together in such a way that $\mathrm{O}$ atoms are face to face and, replace $\mathrm{O}$ by double (=) bond. Thus,
Therefore, alkyne must be

Asked in: AP EAMCET 2009

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