Question

The 2 images of 1,2-dichloromethane are given. Can we call them isomers?

(A) Yes
(B) No
(C) May be
(D) Can’t says

Answer 1

Hint: The C-C bonds undergo rotation about a single bond. In this question we need to see if there is any change in the structure of the molecule. If there is no change in the structure then they will be identical molecules. The C-C single bond has an ability to rotate itself and hence has a structure in which the arrangement in the space is such that it gives the most stable structure.

Step by step explanation:
We have 2 structures of 1,2-dichloromethane in which there is a C-C single bond. This single bond is able to rotate about itself. Thus, on rotation they will be converted to the same structure. Thus, they are homomers.
The isomers when not specified are to be considered as structural isomers and not configurational isomers. Structurally these structures are identical to each other.
Hence option B is the correct answer.

Additional information:
Isomers are compounds in which the molecular formula is the same but the structure is different.
They are mainly of 2 type structural and stereoisomers. In the case of stereoisomers the orientation in the space is different.
Structural isomer is of different types:
Chain isomerism: when 2 or more compounds have the same molecular formula but different carbon skeletons. Example: pentane, isopentane and neopentane.
Positional isomerism:
When 2 or more compounds differ in the position of the functional group. Example: butan-1-ol and Butan-2-ol
Functional group:
2 or more compounds have the same molecular formula but different functional groups. Example: acetaldehyde and acetone.
Metamerism:
It arises due to different alkyl groups on either side of the functional group. It is mostly seen in cases of ether. Ex: methoxypropane and ethoxypropane.
Stereoisomerism:
The compounds that have the same constituent and same sequence on the double bond but differ in relative position of the bond.

Note: We may have a thought that the structures are isomer as the arrangement of the molecules in the space are different. Some can even come to the conclusion that as both the chlorine are on the same side in case of one structure and they are on different sides but the C-C single bond will rotate along itself and hence the structure are same