Q79 P Are the following pairs identica... [FREE SOLUTION]

Chapter 4: Q79 P (page 183)

Are the following pairs identical, enantiomers, diastereomers, or constitutional isomers?

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Identical: If a compound and its mirror image has exactly same structure, the compound is called identical.
Enantiomer: If a compound has a mirror image which is exactly opposite of the original compound, but don鈥檛 superimpose with each other is called enantiomers. Enantiomers also posses a plane of symmetry in a molecule.
Diastereomers: The compounds that has no mirror image, are non-identical and don鈥檛 superimpose with each other is known as diastereomers.
Constitutional isomer: The compounds that has same molecular formula but the connectivity through atoms in a bond are different and has no chiral centre are called constitutional isomers. They are also called structural isomers.

These two compounds don鈥檛 have a mirror plane as well as a plane of symmetry. They are non-identical and don鈥檛 superimpose with each other. So, they are diastereomers.
To understand the nature of the compound, we have to know the R, S name of the chiral centre.

From the Chiral centre and their name, we can see that the R, S nomenclature of these two centres are totally opposite in this two isomers. So, they are exactly opposite to each other for which, they are enantiomers.
The R, S nomenclature of the groups are given below,

Here, both the Cl centre and the CH₃ centres have same R, S nomenclature. So, they are identical compounds.
In case of the 4^th one, the position of the Cl changes in the cyclopentane group, that means in one structure, Cl is in 2 position and in other one, Cl is in 3 position.
So, they are constitutional isomers.