The molecule that possesses S4 symmetry element is -

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HPSC Assistant Professor 2018 Chemistry (Official Paper)
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  1. Allene
  2. Ethylene
  3. Benzene
  4. None of these

Answer (Detailed Solution Below)

Option 1 : Allene
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Detailed Solution

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CONCEPT:

Symmetry Elements in Molecules

  • Symmetry elements in molecules include operations such as rotation (Cn), reflection (σ), and improper rotation (Sn).
  • The S4 symmetry element refers to a fourfold improper rotation axis, combining a 90-degree rotation followed by a reflection through a plane perpendicular to the axis.
  • Only certain molecular geometries allow for this type of symmetry.

EXPLANATION:

  • Structure of allene: F1 Priya Teaching 5 11 2024 D13
  • Allene (C3H4) possesses the S4 symmetry element due to its linear and symmetrical structure, allowing a 90-degree rotation followed by reflection.
  • Ethylene (C2H4) and benzene (C6H6) do not possess the S4 symmetry element due to their molecular geometries.

CONCLUSION:

The correct answer is: Allene

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