AAMC CBT 7, Hydrogen Bonding Question

[davcro]

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Shouldn't there be Hydrogen bonding between the free electron pairs on Chlorine and the Si-H bond?

 

[Melomare17]

from what i learned, hydrogen bonding only occurs between N, O, and F atoms. Anything else and it's not hydrogen bonding anymore.

 

[Temperature101]

Shouldn't there be Hydrogen bonding between the free electron pairs on Chlorine and the Si-H bond?

Like the previous poster only H, N, F, O can make H bonds. Besides the boiling is 33C, which means it is a weak intermolecular attractive force. All the other bond are strong and would have a BP way above 33

 

[syoung]

Yep. Cl doesn't H-bond.

 

[MedPR]

Just to reiterate, N, O, and F are the only hydrogen bond formers on the MCAT.

 

[davcro]

Thanks guys. H bonding is easy now

 

[SaintJude]

Also, as AAMC points out, anything with such a low boiling point probably doesn't exhibit any significant hydrogen bonding.

 

[Buttafuoco]

Just to clarify, H-bonding occurs when H is bonded covalently to N, O, or F. You can get polar interactions between Hs and those electronegative elements between molecules, but they're not as strong as H-bonding because it's the covalent bond between a highly electronegative atom and H that gives it such a strong dipole moment and thus makes them able to interact strongly with other strong dipoles.

 

[SaintJude]

Just to clarify, H-bonding occurs when H is bonded covalently to N, O, or F. You can get polar interactions between Hs and those electronegative elements between molecules, but they're not as strong as H-bonding because it's the covalent bond between a highly electronegative atom and H that gives it such a strong dipole moment and thus makes them able to interact strongly with other strong dipoles.

I just thought you agreed in the other post (with Kaplan) that hydrogen bonding is not a covalent bond.

 

[Buttafuoco]

hydrogen bonding (which isn't actually bonding) is the strong intermolecular attractions that molecules with hydrogens covalently bonded intramolecularly to N, O or F exhibit between each other. The covalent bond between H and N, O or F make a polar bond and then the H is attracted to the electron rich N, O , or F on another molecule and the N, O or F is attracted to the electron poor H on another molecule.

Water is the classic example. See how the dipoles line up and interact with each other? The dotted lines are the H-bonds.

Carboxylic acids can do it even stronger. Look how they line up to H-bond:

 

[SaintJude]

Sorry, I don't understand, You are saying hydrogen bond is NOT a covalent bond and yet covalently bonds to other molecules.

Both intra and intermolecular hydrogen bonds exist.

 

[Buttafuoco]

No, no covalent bond to other molecules. That would be a chemical reaction. The hydrogen bond is the intermolecular attraction between molecules that have covalent bonds between H and N, F, or O. Look at the pictures. The H-bonds are the dotted lines. They represent attractions between the water molecules that are much weaker than covalent bonds (by an order of magnitude).