State the use of ethers in organic chemistry.

How will you obtain ethyl chloride from diethyl ether.

${\mathrm{PCl}}_5$ causes the cleavage of ether linkage $\mathrm{R}-\mathrm{O}-{\mathrm{R}}^{\text{'}}$ forming $\mathrm{RCl}$, ${\mathrm{R}}^{\text{'}}\mathrm{Cl}$ and ${\mathrm{POCl}}_3$.

${\mathrm{C}}_5{\mathrm{H}}_{12}\mathrm{O}$ on reaction with ${\mathrm{PCl}}_5$ forms $2-$chloropropane and $1-$chloroethane as main compounds.

Thus, ${\mathrm{C}}_5{\mathrm{H}}_{12}\mathrm{O}$ is named as

Product $\left(\mathrm{P}\right)$ may be:

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$