Linear Molecules-Gruop Theory

Linear Molecules:

We will examine two linear molecules:

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Chloromethane:



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Ethyne:



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(a) All linear molecules possess an axis lying along the line-of-centers of the atoms which is labeled C_inf because a rotation about this axis by any angle, which is some multiple of 360/inf, will produce an equivalent structure.



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All linear molecules also possess an infinite number of s_v planes containing all of the atoms as well as the C_inf axis.



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(b) In addition to the above symmetry elements, a linear molecule may possess a center of symmetry, i.



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If the molecule has a center of symmetry it will also possess:

(i) An infinite number of C₂ axes passing through the center and perpendicular to the principal axis (C_inf).



(ii) An improper axis, S_inf, corresponding to rotation about the C_inf axis followed by reflection in a plane passing through the center of symmetry and perpendicular to the C_inf axis.