H-bonding

[bonoz]

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So Hydrogen bonding occurs between a hydrogen (attached to an electronegative atom) and another electronegative atom? is that correct?

Can H-bonding occur between amides, imines, and amines? if yes, then how so? is it the H from the alkyl groups H-bonding with nitrogens of other molecules?

Thanks

 

[loveoforganic]

H-bonding occurs between protic hydrogens (i.e. attached to electronegative atoms) and basic atoms (lone pair donor). Attached is amide H-bonding. Due to resonance, the oxygen is the most basic atom, and the only hydrogens that are protic at all are those attached to nitrogen. Can you figure out the others based on this?

 

[bonoz]

Yes, thank you. So that is assuming that the -R groups in amide are hydrogens?

 

[loveoforganic]

Yes. If the nitrogen had two substituents on it, then there would be no protic hydrogens.

 

[capostat]

I need to ask, because I've read on here that R-O-R cannot H-bond, but in that pic you posted, loveoforganic, there is a lone pair from that oxygen making an H-bond.

So is it because the rest of the molecule can H-bond, that that lone pair on O can H-bond too?

 

[matth87]

General Rule:

"Fun" or F O N atoms can hydrogen bond

F - Fluorine
O - Oxygen
N - Nitrogen

They can hydrogen bond to HF, H2O, NH3.

 

[wanderer]

I need to ask, because I've read on here that R-O-R cannot H-bond, but in that pic you posted, loveoforganic, there is a lone pair from that oxygen making an H-bond.

So is it because the rest of the molecule can H-bond, that that lone pair on O can H-bond too?

In water (and alcohols, carboxylic acids and so forth) there is both hydrogen bond donation (partial positive hydrogens donating their partial positive charges to F,O,N) and hydrogen bond acceptance (F,O,N accepting the partially charged hydrogen or, conversely, donating their partial negative charges to hydrogen).
So for example in a pure ether there can't be any hydrogen bonding, but if in solution with something that can function as a hydrogen bond donor such as water or an alcohol, the ether can accept hydrogen bonds.

Edit: The short answer to your question is yes.

 

[capostat]

In water (and alcohols, carboxylic acids and so forth) there is both hydrogen bond donation (partial positive hydrogens donating their partial positive charges to F,O,N) and hydrogen bond acceptance (F,O,N accepting the partially charged hydrogen or, conversely, donating their partial negative charges to hydrogen).
So for example in a pure ether there can't be any hydrogen bonding, but if in solution with something that can function as a hydrogen bond donor such as water or an alcohol, the ether can accept hydrogen bonds.

Edit: The short answer to your question is yes.

ok great, but whenever a question is asked, we are always to assume that the molecule is in an environment all by itself?

 

[wanderer]

ok great, but whenever a question is asked, we are always to assume that the molecule is in an environment all by itself?

Sorry there isn't a single way to answer this, you just have to judge what the answer is based on the question and the other options. Sometimes the "correct" answer is merely the best among the choices given.