Molecule - Polar or Non Polar?

meganw

1. The problem statement, all variables and given/known data

Determine whether each of the following molecules is polar or nonpolar.
(Please note that lone pairs have been omitted for simplicity!)

H
I - C - I
H

2. Relevant equations

Electronegativity, Polarity, Dipole moments

3. The attempt at a solution

It seemed to me like the C and I have the same polarity so the net dipole would have been zero, but the answer says the molecule is Polar. Why?

Thanks for any help with the explanation! =)

-Megan

opuktun

No, I is more electronegative than C because it is halogen.

Note that the molecule adopts a tetrahedral shape. Either way, the dipole moment will go from the in-between of 2 C-H bonds to the in-between of 2 C-I bonds

meganw

I'm sorry I don't get the last part of what you said. Do you think you could explain? =)

Thanks!

opuktun

Read dichloromethane in http://dwb4.unl.edu/Chem/CHEM869E/CH...n/polarity.htm

meganw

Great link! Also, I have another question:

1) H3COCH3 H3CCH2CH3

It says that the first one has the higher boiling point because of dipole forces. Is there some sort of greater dipole between the C and the O? It looks like it might cancel out though?

2) C2H5OH CH3OCH3

Here, would it be the second one, on account of a great mass, London Dispersion forces being the factor that increases the boiling point?

Thanks! I'm starting to get this I think!! =)

-Megan

meganw

And wait, doesn't it say that the tetrahedral would cancel out???

"Tetrachloromethane

The top image show the bond electron density and the bottom image the molecular dipole

m = 0 D"

opuktun

1) Yes, permanent dipole permanent dipole (H3COCH3) is stronger than London Dispersion force (H3CCH2CH3).

2) BP should be C2H5OH (stronger hydrogen bonding) > CH3OCH3 (pdpd)

Yes, CCl₄ would be a non-polar molecule.