Which of the following molecules have P.O.S. and n-fold perpendicular Axis of Symmetry?
(A) s-cis-1,3-Butadiene (B) (glyoxal, s-trans) (C) 2-Butanol (D) Alanine

Question

Which of the following molecules have P.O.S. and n-fold perpendicular Axis of Symmetry? (A) s-cis-1,3-Butadiene (B) (glyoxal, s-trans) (C) 2-Butanol (D) Alanine

TestHub · Accepted Answer

Ans. (B).

Sol. Glyoxal (OHC-CHO) in its planar s-trans form belongs to C₂h: the molecular plane is a plane of symmetry and a C₂ axis perpendicular to it passes through the midpoint of the C-C bond. 2-Butanol and alanine are chiral (no symmetry), and s-cis-1,3-butadiene is C₂v (its C₂ axis lies in the molecular plane, not perpendicular to a plane of symmetry).

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