Chemistry - STEREO ISOMERISM Question with Solution | TestHub
If the compound Pabde is assumed to be square-planar, then how many stereoisomers are possible ? What are the stereochemical relationships among them ? If each of the square planar structures assumes a pyramidal structure, then how many stereoisomers are possible and what is their stereochemical relationship ?
(I) 
(II) 
(III) 
Options:
Answer:
Solution:
Ans. Square-planar : 3 stereoisomers, all achiral, related as diastereoisomers (geometrical isomers). Pyramidal : 6 stereoisomers = 3 pairs of enantiomers.
Sol. Square-planar Pabde : fix a at the top. The remaining three groups can be arranged around the other three corners in 3 distinct ways ((I), (II), (III)). Each form has the molecular plane as a plane of symmetry, so all three are achiral, and they differ in which groups sit trans to each other : they are diastereoisomers (geometrical isomers).
If the molecule is pyramidal instead, each of the three arrangements becomes chiral (no plane of symmetry) and exists as a pair of enantiomers : 3 x 2 = 6 stereoisomers, three pairs of enantiomers.
