Question

Write down the name of the functional group of –CHO.

Answer 1

Hint: The carbon is double bonded to the oxygen atom and hydrogen it attached to it. This functional group is very similar to ketones and they both undergo similar reactions.

Complete step by step answer:
To answer this question firstly we have to discuss what a functional group is. In organic chemistry, functional groups are specific substituents in molecules which are responsible for the characteristic reaction of that molecule.
The same functional groups will undergo similar reactions regardless of the type of molecule it is attached to.
Basically, a functional group is the identity of a certain class of compounds.
We know alcohol, ketone, aldehyde, ester, ether and many more functional groups in organic chemistry.
Molecules with alcohol functional groups will undergo similar kinds of reaction as other molecules with the same functional group. This is true for any other functional group too.
Now let us identify the functional group given to us. The functional group given to us is –CHO. The carbonyl carbon is attached to the oxygen atom which has a hydrogen atom. This functional group is known as an aldehyde.
 –CHO is the characteristic functional group of aldehydes. Here, the carbon occupied in the carbonyl centre (a carbon atom double bonded to an oxygen atom) is also attached to a hydrogen atom, giving us a –CHO group and there can be other substituents on the carbon atom.
The most common example of an aldehyde is formaldehyde, which is $HCHO$.
There are many more examples of aldehydes that we come across in organic chemistry like acetaldehyde, benzaldehyde etc. They all have one thing in common i.e. the functional group –CHO.
We can understand from the above discussion that the name of the functional group of –CHO is aldehyde.
Therefore, the correct answer is aldehyde.

Note: Aldehydes are very similar to ketones. The only difference is ketones have a ‘R’ group instead of the hydrogen atom. Aldehydes with maximum 4 carbons (as well as ketones) are soluble in water due to the possibility of hydrogen bonding. Higher aldehydes (and ketones) do not dissolve in water. Aldehydes undergo reactions similar to ketones like halogenation, oxidation, reduction etc.