Dipole-dipole and london-dispersion IMF

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Lusin_Yengibaryan_3B
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Dipole-dipole and london-dispersion IMF

Postby Lusin_Yengibaryan_3B » Tue Nov 10, 2020 10:44 pm

How do we distinguish between dipole-dipole forces and London dispersion forces. There are some confusing bonds and I can't seem to find a pattern for these two forces. I'm only able to understand the hydrogen bonding FON/NOF bonds because of this pattern/abbreviation? If you know a pattern for distinguishing between Dipole-dipole and London dispersion IMF, please let me know.

chinmayeec 2H
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Re: Dipole-dipole and london-dispersion IMF

Postby chinmayeec 2H » Tue Nov 10, 2020 11:00 pm

Dipole-dipole forces only exist between polar molecules (molecules with a permanent dipole). This electrostatic interaction is created by the permanent differences in electron density throughout the molecule. Nonpolar molecules cannot have dipole-dipole forces.

On the other hand, London dispersion forces exist in both polar and nonpolar molecules. In nonpolar molecules, London dispersion forces are created when molecules without a permanent dipole collide which causes fluctuations in electron clouds and creates a brief attraction. In general, London dispersion forces are basically when electrons of two colliding atoms are in positions that create temporary dipoles which create brief attractions, so they can exist in polar molecules as well. However, London dispersion forces are the only intermolecular force between nonpolar molecules.

Hope that helps!

Chloe Little 3K
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Re: Dipole-dipole and london-dispersion IMF

Postby Chloe Little 3K » Tue Nov 10, 2020 11:01 pm

London dispersion forces occur between all atoms and molecules whereas dipole-dipole interactions can only occur between molecules that have dipoles.

chinmayeec 2H
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Re: Dipole-dipole and london-dispersion IMF

Postby chinmayeec 2H » Sun Nov 22, 2020 1:17 pm

Dipole-dipole interactions occur between molecules that have a permanent dipole moment. Essentially, the molecule as a whole must be polar, not just the bonds within. For example, BF3 contains polar B-F bonds; however, the shape of the molecule allows the dipoles to cancel out and the molecule is nonpolar. Dipole-dipole interactions are always present between polar molecules.

On the other hand, London dispersion forces are present between all molecules but are the only force present between nonpolar molecules.

Hope that helps!

Carolina Gomez 2G
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Re: Dipole-dipole and london-dispersion IMF

Postby Carolina Gomez 2G » Sun Nov 22, 2020 8:59 pm

London dispersion forces occur between all molecules. Dipole-Dipole interactions occur between polar molecules and have permanent dipole moments.

Gian Boco 2G
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Re: Dipole-dipole and london-dispersion IMF

Postby Gian Boco 2G » Sun Nov 22, 2020 11:40 pm

Dipole-dipole interactions occur between the partial positive and partial negative ends of two polar molecules. London-Dispersion Forces occur as a result of temporary and arbitrary electron position within its density, which means it occurs in all molecules.

Kushaal Madadi 2F
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Re: Dipole-dipole and london-dispersion IMF

Postby Kushaal Madadi 2F » Sun Nov 22, 2020 11:45 pm

Dipole-dipole forces occur because a more electronegative species attracts electrons more than the species it is bonded with. As a result, it becomes slightly negative while the other species become slightly positive. These charged species can interact with other charged species in other molecules. On the other hand, London Dispersion Forces literally occur amongst all molecules and are very weak by comparison.

Izamary Marquez 2H
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Re: Dipole-dipole and london-dispersion IMF

Postby Izamary Marquez 2H » Sun Nov 22, 2020 11:57 pm

In the equation for the dipole moment= charge x bond length, will we be given the charge or how would we calculate it?


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