Question

Which compound is different from the others?
(A)\[{\text{Methyl ethyl ketone}}\]
(B)${\text{Pentan - 2 - one}}$
(C)${\text{2 - Pentanone}}$
(D)\[{\text{Methyl propyl ketone}}\]

Answer 1

Hint: To find which compound is different from others, first check the number of carbon atoms present in all compounds. Drawing the structures of the given compounds helps in identifying the similar compounds with different names.

Complete answer:The compound methyl ethyl ketone has one ethyl group and one methyl group attached to a ketone functional group. The ethyl group has two carbon atoms and the methyl group has one carbon atom. The ketone functional group will have one carbon atom. So, there are totally four carbon atoms in methyl ethyl ketone. It is also called as butanone because it contains four carbon atoms and a ketone functional group in the structure. ${\text{Pentan - 2 - one}}$ has a total of five carbon atoms and a ketone functional group. ${\text{2 - Pentanone}}$also has a total of five carbon atoms and a ketone functional group. The compound methyl propyl ketone has one methyl group and one propyl group attached to a ketone functional group. The propyl group has three carbon atoms and the methyl group has one carbon atom. The ketone functional group will have one carbon atom. So, there are five carbon atoms in methyl propyl ketone. Here, methyl ethyl ketone is different from the others because all the other three compounds are different names of the same compound pentanone which has five carbon atoms.
Therefore, option A is the correct answer.

Note:
Remember to check the number of carbon atoms when these types of questions are given. Then check if there are any similar compounds either by drawing the structures of given compounds or by checking the common names of the given compounds.