# Are 6-hydroxyhexan-2-one and hexanoic acid isomers?

Are the following two compounds isomers?

(A) $\ce{CH_{3}-CO-CH_{2}-CH_{2}-CH_{2}-CH_{2}-OH}$

(B) $\ce{CH_{3}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-COOH}$

Although they have the same molecular formula ($\ce{C_{6}H_{12}O_{2}})$, I think that this two compounds are not isomers.

Isomers are compounds having same molecular formula, but a different structural formula.

As they satisfy the above condition, they are isomers and they are structural isomers. Structural isomers have a few variety based on connectivity of constituent atoms.

• Chain : which has a different arrangement of carbon molecules
• Position : different position of same functional group
• Functional : different functional group for the same atoms
• the others (tautomerism, metamerism and ring-chain isomerism)

They are functional isomers as they have different functional groups. First one has a ketone and an alcoholic group, while the second one has a carboxylic acid functional group.

You will come to see that it is easier to recognise structural isomers compared to the rest (stereoisomerism).

When speaking about isomerism, a picture is worth a thousand words:

They are certainly isomers since they have same molecular formula but differ in structural formula and their chemical properties are also different.

Isomers can be classified into structural isomer/constitutional isomer and stereo-isomer. The above compounds are structural isomers and in depth, they are functional isomers which is sub division of structural isomers in which the isomers differ in functional groups.

The compound A has two functional groups ketone and alcoholic groups (priority order ketone> alcoholic group) and compound B has carboxylic acid as functional group and they have same molecular formula.