Hydrogen Bonding vs Dipole-Dipole

[Chris_Butler_1A]

After a review session where we discussed the relative strengths of 3 separate forces--London Dispersion Forces, Dipole-Dipole, and Hydrogen Bonding--I had a little trouble understanding why Hydrogen Bonds have higher energy than Dipole-Dipole interactions. From what I understand, both kinds of interactions involve two atoms with slightly positive and negative charges being pulled together; so why does Hydrogen Bonding have higher energy? Appreciate the help!

[Kayla Law 2D]

Hydrogen bonds are stronger because of the atoms that are involved. Hydrogen bonding involves a H atom bound to a highly electronegative atom like N, O, and F. Since the hydrogen is bound to such an electronegative atom, the electronegative atom is pulling the electron density away from the hydrogen, making the hydrogen more partially positive than if it was bound to any less electronegative atom. The hydrogen will then form an H-bond with a highly electronegative atom (since it is highly electronegative, it will be more partially negative than other atoms). Since the H-bond is between the hydrogen which has a strong partial positive charge, and the O, N, or F that has a strong partial negative charge, the H-bond is stronger than regular dipole-dipole interactions. The resulting H-bond is stronger because of the electrostatic attraction between the stronger partial negative and stronger partial positive charges, and also because of the large difference in electronegativity between the H and the O, N or F. Hope this helps! :)

[Chris_Butler_1A]

Hydrogen bonds are stronger because of the atoms that are involved. Hydrogen bonding involves a H atom bound to a highly electronegative atom like N, O, and F. Since the hydrogen is bound to such an electronegative atom, the electronegative atom is pulling the electron density away from the hydrogen, making the hydrogen more partially positive than if it was bound to any less electronegative atom. The hydrogen will then form an H-bond with a highly electronegative atom (since it is highly electronegative, it will be more partially negative than other atoms). Since the H-bond is between the hydrogen which has a strong partial positive charge, and the O, N, or F that has a strong partial negative charge, the H-bond is stronger than regular dipole-dipole interactions. The resulting H-bond is stronger because of the electrostatic attraction between the stronger partial negative and stronger partial positive charges, and also because of the large difference in electronegativity between the H and the O, N or F. Hope this helps! :)

That definitely does thank you! I imagine this also plays a role in bond length. Since you mentioned that Hydrogen bonding included the highly electronegative N, O, and F, would it be correct to say that the bond lengths between molecules involved in Hydrogen bonding is shorter than those seen in Dipole-Dipole interactions? Or would it be the other way around given the lower of energy of Dipole-Dipole interactions needing to be closer to interact?