Question

Which of the following is not an isomer of Butanal?
(A)2-Butanone
(B)2-methyl propanal
(C)2-Butanol
(D)But-2-en-1-ol

Answer 1

Isomers can be identified on the basis of molecular formula. Molecules with different functional groups can also be isomers of each other. Spatial arrangement of the two molecules which are isomers will be different.

Complete answer:
Butanal is four carbon containing hydrocarbon with aldehyde functional group present.The molecular formula of butanal is ${{C}_{4}}{{H}_{8}}O$ .The structure of butanal is as follows:

Isomers are those molecules which have the same molecular formula, that same number of atoms of each element, with different spatial arrangement. To see which of the options is not the correct isomer of butanal, we will see the structure and molecular formula of each of the options given in the question.
Considering option (A), 2-Butanone. The molecular formula of 2-Butanone is ${{C}_{4}}{{H}_{8}}O$. The structure of 2-Butanone is given as follows:

The molecular formula of 2-butanone is same as that of butanal, but is with different spatial arrangement, therefore, it is the isomer of butanal.
Considering option (B), 2-methyl propanal. The molecular formula of 2-methyl propanal is ${{C}_{4}}{{H}_{8}}O$. The structure of 2-methyl propanal is given as follows:

The molecular formula of 2-methyl propanal is same as that of butanal, but is with different spatial arrangement, therefore, it is the isomer of butanal.
Considering option (C), 2-Butanol. The molecular formula of 2-Butanol is ${{C}_{4}}{{H}_{10}}O$. The structure of is 2-Butanol given as follows:

The molecular formula of 2-butanol is not the same as that of butanal, therefore, it is not an isomer of butanal.
Considering option (D), But-2-en-1-ol. The molecular formula of But-2-en-1-ol is ${{C}_{4}}{{H}_{8}}O$. The structure of But-2-en-1-ol is given as follows:

The molecular formula of But-2-en-1-ol is same as that of butanal, but is with different spatial arrangement, therefore, it is the isomer of butanal.

Therefore, the correct answer is option (C).

Note:
There are different types of isomers. Like, structural isomers. But-2-en-1-ol, 2-methyl propanal, 2-Butanone are structural isomers of butanal. However , other types of isomers are chain isomers, position isomers,functional group isomers,hydration isomers, linkage isomers.