Chemistry - STEREO ISOMERISM Question with Solution | TestHub

Ans. (D) 3.

Sol. In bicyclo[3.3.0]octan-3-one the two ring-junction carbons are stereocentres and are constitutionally equivalent (the C=O lies in the middle of one bridge). The cis-fused ketone (R,S) is meso; the trans-fused ketone exists as an (R,R)/(S,S) enantiomeric pair. Total stereoisomers = 3.