Question

which of the following compounds with molecular formula $C_4{H}_{8}O$
Will not show functional isomers
 $\left(A\right)$ aldehyde and ketone
 $\left(B\right)$ alkene and ketone
 $\left(C\right)$ aldehyde and alkene
 $\left(D\right)$ epoxides and esters

Answer 1

Hint : Isomers are the molecules which have the same molecular formula but different arrangements of atoms in the space . Even though they have the same molecular formula they don’t have the same physical and chemical properties .

Complete step by step answer
Functional isomers are those isomers which have the same molecular formula but different functional groups .
Going through the options
 $\left(A\right)$ $$ Aldehyde and ketone : In the question we have given $C_4{H}_{8}O$ . $$ Butanal is the possible structure from this molecular formula $C{H}_{3}C{H}_{2}C{H}_{2}CHO$ this is an aldehyde .
2-Butanone which is a ketone can also be formed $C{H}_{3}COC{H}_{2}C{H}_3$
So , these two show functional isomers .
 $\left(B\right)$ Alkenol or alcohol the possible structure is cyclobutanol . ketone will be 2 butanone so these two will also show functional isomerism .
 $\left(C\right)$ Similarly if we take aldehyde and alkene then they will also show functional isomerism .
 $\left(D\right)$ Now if we take epoxides to form a cyclic ring with three atoms . which is like an equilateral triangle , it is highly reactive.
Now in case of esters , it has two oxygen in its structure and the molecular formula given contains one oxygen atom , it is obtained by the reaction of carboxylic acid and alcohol .
 so clearly epoxides and esters are not functional isomers .
Option $\left(D\right)$ will be the answer.

Note
The molecular formula have lots of functional isomers some are cis-2,3 epoxy butane , trans-2,3epoxybutane , methoxy cyclopropane , allyl methyl ether , crotyl alcohol etc. there are many other isomers like position isomers , chain isomers ,skeletal isomers etc.