Chemistry - STEREO ISOMERISM Question with Solution | TestHub
Match the following :
(I) 
(II) 
(III) 
(IV) 
Column I | Column II |
|---|---|
(A) Plane of symmetry | (P) I |
(B) Centre of symmetry | (Q) II |
(C) Show geometrical isomerism | (R) III |
(D) Show optical isomerism | (S) IV |
Options:
Answer:
Solution:
Ans. A Q, R; B P; C P, Q, S; D S.
Sol. I (the substituted cyclobutane with H and Ph on C-1, COOH and Ph... ): a 180-degree rotation about the ring centre maps every group onto an identical group (H into H, Ph into Ph, COOH into COOH with up/down interchanged) : centre of symmetry present, no plane; the ring has cis/trans (geometrical) isomerism but is achiral, so it shows G.I. but not O.I. : B P, C P.
II : a plane of symmetry through the diagonal carrying the two COOH-bearing carbons maps one Ph/H carbon onto the other : plane of symmetry present, G.I. shown, no O.I. : A Q, C Q.
III (4-methylcyclohexylidene allene-acid) : the two ring paths from the allene carbon are identical (mirror-related through C-4), and the plane through the allene axis carrying the H and COOH is a mirror plane : the molecule is ACHIRAL, has a plane of symmetry, and shows neither optical nor geometrical isomerism : A R.
IV (3-methylcyclohexylidene allene-acid) : chiral, no symmetry, shows O.I., and with the Me on the side of COOH (or opposite) it also shows geometrical isomerism : C S, D S.
