General Chem question

Started by jdx915
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jdx915

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I was just going through the problems in the Kaplan book again and it says the HCl is dipole-dipole, but isint this H-bonding since it is a Hydrogen attached to an electronegative atom?
 
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I believe "true" hydrogen-bonding occurs between hydrogen and the very electronegative atoms - N, O, and F.
While Cl has the same EN as N, I believe Cl having 7 valence electrons has something to do with it (why it's not a "true" hydrogen bond).

Maybe someone can expand on that (or correct me if I'm wrong 😉)?
 
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jdx915 said:
I was just going through the problems in the Kaplan book again and it says the HCl is dipole-dipole, but isint this H-bonding since it is a Hydrogen attached to an electronegative atom?
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I remember this problem showed up on the Cliffs too. If you think about this problem for another minute you realize that H-bonding occurs between two molecules. For example, water has H-bonding. Why? Not because Oxygen is attached to a Hydrogen. Instead, H-Bonding occurs between the electronegative Oxygen of one molecule with a Hydrogen of another molecule (I wish I could draw this out).
 
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TheRxQueen said:
I believe "true" hydrogen-bonding occurs between hydrogen and the very electronegative atoms - N, O, and F.
While Cl has the same EN as N, I believe Cl having 7 valence electrons has something to do with it (why it's not a "true" hydrogen bond).

Maybe someone can expand on that (or correct me if I'm wrong 😉)?
Click to expand...

Yep, it's dipole-dipole, which is why HCl is a gas (hydrochloric acid is a solution of this gas in water). If it were hydrogen bonding it would probably be a liquid at room temperature.

The electronegativity is explained by shielding. As you go across a period, there are more protons, so electrons are more strongly pulled to the atom. When you go down a group, there is another electron shell in the way, increasing the distance to the nucleus. If you remember your physics, you'll know that the attraction between oppositely charged particles decreases with distance.
 
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