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Molecule - Polar or Non Polar?

by meganw
Tags: molecule, polar
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meganw
#1
Feb1-09, 12:32 PM
P: 96
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
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opuktun
#2
Feb1-09, 12:51 PM
P: 30
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
#3
Feb1-09, 12:54 PM
P: 96
I'm sorry I don't get the last part of what you said. Do you think you could explain? =)

Thanks!

opuktun
#4
Feb1-09, 01:21 PM
P: 30
Molecule - Polar or Non Polar?

Read dichloromethane in http://dwb4.unl.edu/Chem/CHEM869E/CH...n/polarity.htm
meganw
#5
Feb1-09, 01:37 PM
P: 96
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
#6
Feb1-09, 01:39 PM
P: 96
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
#7
Feb1-09, 01:49 PM
P: 30
Quote Quote by meganw View Post
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)

Quote Quote by meganw View Post
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.


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