H-F H-F Hydrogen Bonding vs Dipole-Dipole

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Sunny Wu 3A
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H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Sunny Wu 3A » Thu Nov 12, 2020 8:37 pm

In Lecture 17, Dr. Lavelle listed H-F H-F as an example of a dipole dipole interaction with an approx. energy of -2 kJ/mol:

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However, wouldn't this attraction be more specifically classified as hydrogen bonding, and so wouldn't the energy be approx. -20 kJ/mol?

Adrienne Chan 1G
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Adrienne Chan 1G » Thu Nov 12, 2020 8:56 pm

Not an answer per se, but I had the exact same question. Fluorine is even more electronegative than oxygen, so I thought, if anything, the hydrogen bonding between HF molecules would be stronger. Curious to see if anyone understands Lavelle's thought process!

Ke Huang 2G
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Ke Huang 2G » Thu Nov 12, 2020 10:57 pm

I think both hydrogen bonding and dipole-dipole forces are involved. The -2kj/mole might only represent the dipole-dipole force.

Laura 3l
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Laura 3l » Fri Nov 13, 2020 12:40 am

I believe since this is a dipole dipole force then it would also be a Hydrogen bond.

Darren1j
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Darren1j » Fri Nov 13, 2020 4:30 pm

I had this same question and I think there's a reason for that difference. In this case H-F H-F, I think its classified as a hydrogen bond and therefore would be -20 but other dipole-dipole interactions that are not hydrogen bonding would be around -2. H Bond is Dipole-Dipole, but dipole- dipole doesn't have to be h-bond.

Charlotte Adams 1A
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Charlotte Adams 1A » Fri Nov 13, 2020 4:34 pm

I am also confused because we in the HW we were shown an H-F bonding to another H-F and it said the intermolecular force shown was hydrogen bonding.

Joanna Huang
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Joanna Huang » Fri Nov 13, 2020 5:29 pm

I believe both Hydrogen bonding and Dipole-Dipole forces are at work! Since one molecule is strongly polar (F), the polar ends of the molecule will attract the hydrogen. Because hydrogen only needs one pair of electrons, it can also form a hydrogen bond with F, which is strongly electronegative.

Shrinidhy Srinivas 3L
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Shrinidhy Srinivas 3L » Fri Nov 13, 2020 5:47 pm

You're right when you say that hydrogen bonding is involved here. However, I believe that Dr. Lavelle was just referring to the fact that H-F has both dipole-dipole interactions and hydrogen bonding. Both have separate energies. Hope this helps!

Izamary Marquez 2H
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Izamary Marquez 2H » Fri Nov 13, 2020 10:40 pm

In addition, when calculated a dipole moment, will |q| always be given?

ShinwooKim_3E
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby ShinwooKim_3E » Sat Nov 14, 2020 12:01 am

H-F has both hydrogen bonds and dipole-dipole bonding!

Xavier Herrera 3H
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Xavier Herrera 3H » Sat Nov 14, 2020 9:42 pm

The bond between the H and the F would be both a dipole-dipole bond and a hydrogen bond, since hydrogen bonds are basically stronger versions of regular dipole-dipole bonds. So, I would think that this attraction should be -20kj/mol, rather than -2kj/mol.

Charlotte Adams 1A
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Re: H-F H-F Hydrogen Bonding vs Dipole-Dipole

Postby Charlotte Adams 1A » Sun Nov 15, 2020 11:09 am

Izamary Marquez 2L wrote:In addition, when calculated a dipole moment, will |q| always be given?

I don't think we will have to calculate the dipole for the test.


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