Chemistry - STEREO ISOMERISM Question with Solution | TestHub
Discuss the stereochemistry of these compounds. The diagrams are deliberately poor ones that are ambiguous about stereochemistry - your answer should use good diagrams that show the stereochemistry clearly.
(1) 
(2) 
(3) 
(4) 
(5) 
Options:
Answer:
Solution:
Ans. (1) cis and trans, both chiral. (2) one achiral compound (POS). (3) E and Z diastereoisomers, each a pair of enantiomers. (4) syn (meso) and anti (chiral pair). (5) syn (meso) and anti (chiral pair).
Sol. (1) 1-Fluoro-2-chlorocyclopropane: two non-equivalent stereocentres; cis and trans diastereoisomers, each existing as a pair of enantiomers - both chiral. (2) 1,1-Dichloro-2-methylcyclopropane: a plane through C2 and C3 bisects the C1(Cl)2 group : a single achiral compound. (3) 4-Chloropent-2-ene: the double bond is stereogenic (E and Z diastereoisomers) and C4 is a stereocentre, so each of the E and Z forms is chiral (a pair of enantiomers each). (4) Hydrobenzoin, Ph-CH(OH)-CH(OH)-Ph: two equivalent stereocentres; the syn (2R,3S) form is meso (achiral) and the anti (2R,3R)/(2S,3S) forms are a chiral enantiomeric pair. (5) 1,2-Dichloro-1,2-difluoroethane: two equivalent stereocentres; the syn (R,S) form is meso and the anti (R,R)/(S,S) forms are a chiral enantiomeric pair.
