Concept: D. Hydrogen Bonding
Hydrogen Bonding is a special kind of dipole-dipole interaction. When a hydrogen is covalently bonded to a highly electronegative element (oxygen, nitrogen, or fluorine), the dipole formed is quite strong, leaving a partial positive charge on the hydrogen atom and a partial negative charge on the other atom. If this hydrogen atom is close to another electronegative atom with a partial negative charge, a hydrogen bond is formed. A hydrogen bond is not a true bond, but just a very strong dipole-dipole interaction.
Hydrogen bonds only form if all of the following conditions are met:
- A hydrogen is directly bonded to one of the three most electronegative elements: nitrogen, oxygen, or fluorine.
- Another of those electronegative elements has a lone pair of electrons available to accept a hydrogen bond.
In a hydrogen bond, the atom chemically bonded to the hydrogen does not have to be the same atom as the hydrogen bond acceptor.