Question

an alkene A on ozonolysis gives a mixture of ethanol and pentan-3-one.write structure and IUPAC naem of A

Answer 1

In the given alkene, the structure can be obtained by getting the ozonide structure and so the alkene has been detected as 3-Ethylpent-2-ene.

Answer 2

The ozonolysis of alkene results the formation of carbonyl compounds. Here $O_{3}$ is added on double bonded carbon atoms of the alkene and convert both the double bonded C atoms changes to carbonyl carbon atom.  

$\bold{\left(\mathrm{CH}_{3}-\mathrm{CH}_{2}\right)_{2}-\mathrm{C}=\mathrm{CH}_{2} \mathrm{CH}_{3}+\mathrm{O}_{3} \rightarrow \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{OH}+\mathrm{CH}_{3} \cdot \mathrm{CH}_{2}-\mathrm{CO}-\mathrm{CH}_{2}-\mathrm{CH}_{3}}$

Hence the alkene must be 3-ethyl-2-pentene as the $O_{3}$ molecule will add on double bonded C atoms and  the double bond breaks to form alcohol and ketone here as the final product. The reaction occurs with the formation of ozonoid intermediate.