The correct statement regarding elements of symmetry and chirality of ...
Presence of either plane of symmetrical or centre of symmetry. Optical activity of one half of the molecule is exactely cancelled by other half and is internally compensated.
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The correct statement regarding elements of symmetry and chirality of ...
Symmetry and Chirality in Compounds
Introduction:
In organic chemistry, symmetry and chirality are important concepts that are used to describe the three-dimensional arrangement of atoms in a molecule. Symmetry refers to the presence of certain elements, such as an axis or plane, that divide the molecule into symmetrical parts. Chirality, on the other hand, relates to the presence of a non-superimposable mirror image in a molecule.
Options:
Let's discuss each option one by one to determine the correct statement regarding elements of symmetry and chirality in compounds.
a) Presence of an axis of symmetry destroys chirality:
This statement is correct. An axis of symmetry is a line through a molecule that divides it into two symmetrical halves. If a molecule possesses an axis of symmetry, it means that its mirror image can be superimposed onto it. In other words, the molecule is achiral. Chirality requires a lack of symmetry, so the presence of an axis of symmetry destroys chirality.
b) Centre of symmetry has no role to play in chirality of a compound:
This statement is incorrect. A center of symmetry is a point in a molecule where a line drawn from any atom through the center intersects an equivalent atom on the opposite side. If a molecule possesses a center of symmetry, its mirror image can be superimposed onto it. Hence, a compound with a center of symmetry is achiral.
c) A compound with either plane or center of symmetry is always achiral:
This statement is correct. A compound with either a plane of symmetry or a center of symmetry is always achiral. A plane of symmetry divides a molecule into two identical halves, and a center of symmetry reflects the molecule through a point. In both cases, the mirror image of the molecule can be superimposed onto it, making it achiral.
d) A compound with an axis of symmetry simultaneously contains a center of symmetry:
This statement is incorrect. An axis of symmetry and a center of symmetry are two different symmetry elements. It is possible for a compound to have an axis of symmetry without a center of symmetry, and vice versa. Therefore, a compound with an axis of symmetry does not necessarily contain a center of symmetry.
Conclusion:
Based on the analysis of each statement, the correct statement regarding elements of symmetry and chirality in compounds is option 'C'. A compound with either a plane or center of symmetry is always achiral. This is because the presence of these symmetry elements allows the mirror image of the molecule to be superimposed onto it, destroying chirality.
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