Dipole Moment

[Chiara Frank]

Hi! I have been reviewing the notes from the lecture on dipole moments, and I believe I have a good understand, however I was confused about something mentioned on the Achieve homework pertaining to these. After explaining the location of the negative pole within each molecule, the solution mentions that the polar bonds in COF2 nearly cancel each other out, so COFH has the greater dipole moment. I was unsure of what are the conditions or what must happen for polar bonds to cancel each other out? Thank you!

[Shria G 2D]

Hi,
I think you can figure out if polar bonds cancel each other out if you think of them as vectors pointing in the direction of the more electronegative atom. If there are vectors that are equal in magnitude and opposite in direction, they would cancel out. For that achieve problem, in COF2, C and O have a similar electronegativity difference to C and F and if you look at the vector diagram that they have in their solution, the vectors nearly cancel out. However, for COFH, the C-H bond is nonpolar and the resulting vector from all of the bonds is far from cancelling out, meaning that its dipole moment is greater.

[Mikayla 2G]

Another helpful concept for me is the geometry/ symmetry of the molecule. The more symmetric (with shape and EN), the less polar a molecule will be

[AJackman]

If two equivalent dipoles are pointing in opposite directions, they cancel each other out because the pull of one of the central atom negates the pull of the other.

[Lynne Xu 3K]

I find it helpful to use the geometry of the molecule to determine whether the dipoles cancel out. The electrons will be pulled towards the more electronegative element, so you can draw all the individual dipoles (vectors). If two vectors go in opposite directions, they will cancel out.

[605721741]

The CF dipole is different from CH dipole. Thats why in COFH, the dipoles don't cancel. Whereas in COF2 they do!

[Arpita Padhy 3E]

I just like to think of the direction in which each atom is pulling to see if they pull in different directions which would cause them to cancel each other out.

[Luke Schwuchow 14A]

When we look at dipoles that cancel, we have to look at their shape. In this case, COF2 is trigonal planar, meaning the dipoles pull in oposite directions and their forces cancel. The reason why this case "nearly" cancles is because Carbon has 2 different kinds of atoms bonded to it. These 2 atoms have different electronegativities and therefore cannot perfectly cancel eachother out.

[Leah Wildmann 1F]

Dipole moments cancel out if the atoms pulling the electrons have similar electronegativities. The arrangement of the atoms or the shape also has to be in a way that the dipoles cancel out.

[Ashley Fakolujo 3H]

Hi,
I think you can figure out if polar bonds cancel each other out if you think of them as vectors pointing in the direction of the more electronegative atom. If there are vectors that are equal in magnitude and opposite in direction, they would cancel out. For that achieve problem, in COF2, C and O have a similar electronegativity difference to C and F and if you look at the vector diagram that they have in their solution, the vectors nearly cancel out. However, for COFH, the C-H bond is nonpolar and the resulting vector from all of the bonds is far from cancelling out, meaning that its dipole moment is greater.

Isn’t it also that whenever a hydrogen bond is present, you’ll have a dipole moment regardless?