What kind of intermolecular forces are present in the following compounds: C Cl_4, CH_2Cl_2, CH_3OH, CO_2, SCl_4, and SCl_6?

1 Answer
Aug 16, 2016

Warning! Long answer. Here's what I get.

You have to draw the Lewis structure of each molecule, use VSEPR theory to determine its shape, and then decide whether or not the bond dipoles cancel.

"CO"_2 and "CCl"_4

CO2 and CCl4CO2 and CCl4
(From www.peoi.org)

"CO"_2 is a linear molecule with an "O-C-O" bond angle of 180°. The bond dipoles are equal and in opposite directions, so they cancel.

"CO"_2 is a nonpolar molecule. Its strongest intermolecular forces are London dispersion forces.

"CCl"_4 is a tetrahedral molecule with a "Cl-C-Cl" bond angle of 109.5°.

The two "C-Cl" bond dipoles in the plane of the paper have a resultant pointing to the right at an angle of 54.75° from the vertical.

The two "C-Cl" bond dipoles behind and in front of the paper have an equal and opposite resultant to the first.

Since the bond dipoles are equal and in opposite directions, they cancel.

"CCl"_4 is a nonpolar molecule. Its strongest intermolecular forces are London dispersion forces.

"CH"_2"Cl"_2

preparatorychemistry.compreparatorychemistry.com

"CH"_2"Cl"_2 has a tetrahedral shape. The two "C-Cl" bond dipoles have a resultant that bisects the "Cl-C-Cl" bond angle.

"CH"_2"Cl"_2 is therefore a polar molecule, and its strongest intermolecular forces are dipole-dipole forces.

"CH"_3"OH"

"CH"_3"OH" has a highly polar "O-H" bond. The "O" atom has a high δ^"-" charge, and the "H" of the "OH" has a high δ^+ charge.

employees.csbsju.eduemployees.csbsju.edu

The "O" in one molecule is strongly attracted to the "H" in another molecule, and the "H" in one molecule is strongly attracted to the "O" in another molecule.

The strongest intermolecular force in "CH"_3"OH" is hydrogen bonding.

"SCl"_4

See-SawSee-Saw
(From en.wikipedia.org)

"SCl"_4 has a see-saw shape.

The two horizontal "S-Cl" bond dipoles cancel, but the downward-pointing dipoles reinforce each other.

"SCl"_4 is a polar molecule, and its strongest intermolecular forces are dipole-dipole forces.

"SCl"_6

"SCl"_6is an octahedral molecule.

upload.wikimedia.orgupload.wikimedia.org

Every "S-Cl" bond dipole has a partner pointing in exactly the opposite direction, so all bond dipoles cancel.

"SCl"_6 is a nonpolar molecule, so its strongest intermolecular forces are London dispersion forces.