Question

What is the IUPAC name of $C{{H}_{3}}CHO$?
(a) Acetal
(b) Methanal
(c) Ethanal
(d) Acetaldehyde

Answer 1

Hint: IUPAC stands for International Union of Pure and Applied Chemistry. One should recall that -$CHO$ group belongs to the aldehyde group.

Complete Step by Step Solution:
Now for the given name, the structure looks somewhat like,
$C{{H}_{3}}-CH=O$

• Here the $CHO$ group is the aldehyde group and the IUPAC name ends with –al.
• Also the primary group attached to the $CHO$ group is Methyl group.
• Hence the IUPAC name of the compound would be Ethanal because of two carbons in the chain, which is option C.
• Option A, which is Acetal, is actually a functional group. They are germinal-diether derivatives of aldehydes or ketones. Although, ketone derivatives of this kind are called Ketals.
• Option B here which is Methanal, here in the case of methanal, the group that makes bond with the $CHO$ group is merely $H$.
• The chemical structure would look like:
$H-CH=O$
• Option D, which is Acetaldehyde is the same as Ethanal but it is the common name of the same and not the IUPAC name.
• Hence, the correct answer to the above question is Option C which is Ethanal.

Note: Students often confuse Ethanal and Acetaldehyde in this type of problem. One should carefully go through their basic concepts. Acetaldehyde and Ethanal are the same technically, but one is the proper IUPAC name (Ethanal) whereas Acetaldehyde is the common name, normal day to day usage name. Next in this homologous series are Butanal, Propanal, Pentanal and so on.