Hydrogen bond vs dipole-dipole?

In summary, hydrogen bonds are a stronger version of dipole-dipole interactions where one side of a molecule has a positive charge and the other side has a negative charge. They have a magnitude of 0.5 eV, which is smaller than covalent bonds but larger than van der Waals forces. These bonds can be observed in all phases of water, with ice having a high melting and boiling point due to the presence of hydrogen bonds. Additionally, hydrogen bonds involve a transfer of charge between bonded molecules and cannot be solely explained by dipole-dipole interactions.
  • #1
jaydnul
558
15
I saw a video on youtube saying water molecules were held together by hydrogen bonding, not dipole dipole. Why is that?
 
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  • #2
Hydrogen bonds are special (stronger) version of dipole-dipole interactions.
 
  • #3
I have heard this statement before but I have no idea what it means. I think I know what dipole-dipole interactions are but I'm not sure about their relation to hydrogen bonds and conversely. Could you please elaborate?
 
  • #4
Hydrogen bonds are bonds where one side of molecule A has a positively charged region (hydrogen, usually connected to oxygen) and one side of molecule B has a negatively charged region (usually oxygen). As both molecules are uncharged (otherwise, it would be an ionic bond), they have to be dipoles.
 
  • #5
But two H atoms or two H2 molecules undergo dipole-dipole dispersive interactions without having permanent dipoles. Likewise for two orientation-averaged H2O molecules. What's the magnitude of a typical hydrogen bond? Can it be measured in any or all phases of H2O?
 
  • #6
hydrogen bonds are in the 0.5 eV range.

for comparison, covalent bonds are in the single eVs while van der Waals forces are in the 0.1 eV range.

Of course in chemistry we more often talk about kJ/mol but those are hard numbers to compare when visualizing single bonds. eV are easy to compare to other things since we know the ionization energy of H atoms in eV.

You might notice, hey, hydrogen bonds and van der Waals forces don't seem all that different. However in the regime of low energies, even a tiny difference is huge.
 
  • #7
AbdulQat said:
But two H atoms or two H2 molecules undergo dipole-dipole dispersive interactions without having permanent dipoles.
Van der Waals

Likewise for two orientation-averaged H2O molecules.
Their orientations are correlated, which gives an effective attraction even if the average orientation of each atom is random.

Can it be measured in any or all phases of H2O?
Ice is like many frozen hydrogen bonds, and the high melting/boiling point is a result of hydrogen bonds in ice and water. As gas, interactions between atoms are weak as always.
 
  • #8
Although I don't remember the percentages, in hydrogen bonds there is also a considerable transfer of charge between the bonded molecules and other effects which can't be subsumed under dipole-dipole interaction.
 

Related to Hydrogen bond vs dipole-dipole?

1. What is the difference between a hydrogen bond and a dipole-dipole interaction?

A hydrogen bond is a specific type of dipole-dipole interaction that occurs between a hydrogen atom and a highly electronegative atom, such as oxygen or nitrogen. It is a stronger type of dipole-dipole interaction due to the large difference in electronegativity between the two atoms involved.

2. How does the strength of a hydrogen bond compare to a dipole-dipole interaction?

A hydrogen bond is generally stronger than a regular dipole-dipole interaction. This is because the hydrogen bond involves a highly electronegative atom, resulting in a larger separation of charge and a stronger attraction between the molecules.

3. What types of molecules can form hydrogen bonds?

Molecules that contain hydrogen bonded to a highly electronegative atom, such as oxygen, nitrogen, or fluorine, can form hydrogen bonds. Common examples include water, ammonia, and hydrogen fluoride.

4. How do hydrogen bonds contribute to the properties of water?

Hydrogen bonds between water molecules give it unique properties, such as high surface tension, boiling point, and heat capacity. These bonds also allow water to dissolve many substances, making it an excellent solvent.

5. Can dipole-dipole interactions occur between non-polar molecules?

No, dipole-dipole interactions only occur between polar molecules. Non-polar molecules have a symmetrical distribution of charge and therefore do not have a dipole moment, making them unable to form dipole-dipole interactions.

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