Chemistry - STEREO ISOMERISM Question with Solution | TestHub
Discuss the stereochemistry of these compounds. (Hint. This means saying how many diastereoisomers there are, drawing clear diagrams of each, and saying whether they are chiral or not.)
(1) 
(2) 
(3) 
(4) 
Options:
Answer:
Solution:
Ans. (1) and (2): one compound each, achiral. (3): two diastereoisomers - cis (meso, achiral) and trans (chiral pair). (4): two diastereoisomers - cis and trans, both chiral.
Sol. (1) Cyclobutane: every carbon is CH2; no stereogenic element - a single achiral compound, no diastereoisomers. (2) 3,3-Dimethylcyclobutanone: C3 bears two identical methyls and the carbonyl carbon is planar; no stereogenic element - a single achiral compound. (3) Bicyclo[3.1.0]hexane: the two ring-junction carbons are stereocentres. The cis-fused form is meso (internal plane, achiral); the trans-fused form is chiral and exists as a pair of enantiomers : two diastereoisomers. (4) 1-Bromo-2-chlorocyclopropane: two non-equivalent stereocentres. The cis and trans forms are diastereoisomers, and each is chiral (a pair of enantiomers each) : two diastereoisomers, both chiral.
