Molecule - Polar or Non-Polar?

[meganw]

Homework Statement

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

Homework Equations

Electronegativity, Polarity, Dipole moments

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/CHEM869ELinks/www.uis.edu/7Etrammell/organic/introduction/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]

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

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

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

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"

Yes, CCl₄ would be a non-polar molecule.