Rod-shaped vs spherical molecules

[Marcus1H]

Hi, would someone mind explaining how instantaneous dipoles are stronger in rod shaped molecules than spherical shaped molecules and how to tell if a molecule is rod shaped or spherical.

[Tamer Siam 2F]

In rod shaped, there is less distance between the partial charges of the molecule, so the electrostatic attraction is stronger, compared to a spherical shape, where one curve is close, while the other is really far away (2 diameters away). Pretty sure you can tell if it's rod shaped or spherical shaped from the lewis structure: if the structure forms a circle shape, it's spherical; if it forms a line (like a polymer chain), then rod shaped.

[Leslie_C_2J]

Hi,

The reason why instantaneous dipoles are stronger in rod shaped molecules than spherical molecules is because there is more surface area for the molecules to interact. Additionally, electrons are able to move more freely along the length of the rod shaped molecule, which makes the dispersion forces stronger. To tell the difference look at the structure of the molecule. Long, chain like structures tend to be rod shaped and symmetrical structures are closer to spherical. Hope this helps!