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Hydrogen Bonds

Can anyone tell me why hydrogen bonds can't form - it has oxygen in it doesn't it - so doesn't that mean when they interact with other molecules they form hydrogen bonds.
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Original post by Linked
Can anyone tell me why hydrogen bonds can't form - it has oxygen in it doesn't it - so doesn't that mean when they interact with other molecules they form hydrogen bonds.


no. the hydrogen has to be bonded to an oxygen (or another very electronegative element such as F) in order to have hydrogen bonds. In your example, the hydrogens are only bonded to carbons
Reply 2
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Original post by Plato's Trousers
no. the hydrogen has to be bonded to an oxygen (or another very electronegative element such as F) in order to have hydrogen bonds. In your example, the hydrogens are only bonded to carbons


Ok thank you very much.

Really appreciate it - all this time I had the wrong idea and now you've cleared it all the other concepts become more apparent.
Original post by Linked
Ok thank you very much.

Really appreciate it - all this time I had the wrong idea and now you've cleared it all the other concepts become more apparent.


no probs. It's basically a dipole dipole interaction due to the highly polarized nature of a H-O or H-F bond (since H has an electronegativity value of 2.2 whereas O is 3.4 and F is 4.0)

See this table.

https://en.wikipedia.org/wiki/Electronegativities_of_the_elements_(data_page)
Reply 4
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Original post by Plato's Trousers
no probs. It's basically a dipole dipole interaction due to the highly polarized nature of a H-O or H-F bond (since H has an electronegativity value of 2.2 whereas O is 3.4 and F is 4.0)

See this table.

https://en.wikipedia.org/wiki/Electronegativities_of_the_elements_(data_page)



So correct me if I'm wrong please;

Hydrogen bonding arises because of the greater dipole moments with O, F, N. Since these are more electronegative than others there is a greater dipole moment, hence give rise to these hydrogen bonding?
Original post by Linked
So correct me if I'm wrong please;

Hydrogen bonding arises because of the greater dipole moments with O, F, N. Since these are more electronegative than others there is a greater dipole moment, hence give rise to these hydrogen bonding?


Basically yes. It's because of all the elements involved in covalent bonds, H has the lowest electronegativity and O and F have the highest. You therefore get especially big dipole moments between them which lead to particularly strong dipole-dipole interactions. They are so marked that they have been given a special name "hydrogen bonds" but they are really just a case of dipole-dipole interactions.
(edited 10 years ago)
Reply 6
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Original post by Plato's Trousers
Basically yes. It's because of all the elements involved in covalent bonds, H has the lowest electronegativity and O and F have the highest. You therefore get especially big dipole moments between them which lead to particularly strong dipole-dipole interactions. They are so marked that they have been given a special name "hydrogen bonds" but they are really just a case of dipole-dipole interactions.

(N is usually not included AFAIK as it's on the borderline of being electronegative enough)


Thank you so much - you are a god send:smile:
Reply 7
Avatar for Liz958
Liz958
Hydrogen bonding only arises between polar molecules such as water. The actual force of attraction is between the slightly positive hydrogen (due to weaker attraction to shared pair of electrons in a covalent bond) and the lone pair on a O, N or F molecule. The molecule in the question is non-polar and the oxygen has no lone pairs, so there are no hydrogen bonds. I think..
(edited 10 years ago)
Original post by Plato's Trousers
Basically yes. It's because of all the elements involved in covalent bonds, H has the lowest electronegativity and O and F have the highest. You therefore get especially big dipole moments between them which lead to particularly strong dipole-dipole interactions. They are so marked that they have been given a special name "hydrogen bonds" but they are really just a case of dipole-dipole interactions.


Original post by thelion0
x


Why did you neg me for this post??



Original post by Liz958
Hydrogen bonding only arises between polar molecules such as water. The actual force of attraction is between the slightly positive hydrogen (due to weaker attraction to shared pair of electrons in a covalent) and the lone pair on a O, N or F molecule. The molecule in the question is non-polar and the oxygen has no lone pairs, so there are no hydrogen bonds. I think..


This is not correct. The molecule in the OP's question is polar and the oxygen has two lone pairs. Hydrogen bonding is not between hydrogen and a lone pair
(edited 10 years ago)
Reply 9
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Liz958
Original post by Plato's Trousers
Why did you neg me for this post??





This is not correct. The molecule in the OP's question is polar.


oh right sorry.. It's because C - H bonds are non-polar so there's no attraction between hydrogen atoms and the oxygen's lone pairs.. (The oxygen does have lone pairs - my mistake) but then again I might be completely wrong again
Original post by Liz958
oh right sorry.. It's because C - H bonds are non-polar so there's no attraction between hydrogen atoms and the oxygen's lone pairs.. (The oxygen does have lone pairs - my mistake) but then again I might be completely wrong again


that's not correct either.

1) C-H bonds are polar - because C and H have different electronegativities
2) hydrogen bonding is nothing to do with lone pairs
Original post by Liz958
oh right sorry.. It's because C - H bonds are non-polar so there's no attraction between hydrogen atoms and the oxygen's lone pairs.. (The oxygen does have lone pairs - my mistake) but then again I might be completely wrong again


C-H bonds are polar, because they have different electronegativities. However, the electronegativity difference between C and H is negligible, so we say that C-H bonds are effectively non-polar.

Hydrogen bonds are intermolecular forces, which are formed when a hydrogen atom is bonded to a very electronegative atom, such as fluorine, oxygen or nitrogen. When a hydrogen atom is bonded to a chlorine atom, e.g. in hydrogen chloride, you have permanent dipoles forming and not hydrogen bonds, because chlorine atoms are not as electronegative as fluorine, oxygen or nitrogen atoms.

In this case, OP, no hydrogen atoms are bonded to any electronegative atoms mentioned above, so hydrogen bonds may not form between ethoxyethane molecules. :smile:
Original post by Plato's Trousers
2) hydrogen bonding is nothing to do with lone pairs


:erm: yes it is :p:

A hydrogen is attracted to the lone pair on an electronegative element/group - it's what gives it its directionality :yes:
Reply 13
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Liz958
Original post by Plato's Trousers
that's not correct either.

1) C-H bonds are polar - because C and H have different electronegativities
2) hydrogen bonding is nothing to do with lone pairs


Difference in electronegativity is small so it's considered non-polar and yes it does have to do with lone pairs but I guess not in this case.... thegodofgod explains everything much better - so you can ignore me :smile:
Original post by EierVonSatan
:erm: yes it is :p:

A hydrogen is attracted to the lone pair on an electronegative element/group - it's what gives it its directionality :yes:


well, ok, let me re-phrase that. hydrogen bonding is not primarily about lone pairs. It's primarily about a large dipole moment between H and O or F. Lone pairs add a dimension to it, I agree. But if it were primarily about lone pairs, you would see H bonding in ethers and you don't
Original post by Plato's Trousers
well, ok, let me re-phrase that. hydrogen bonding is not primarily about lone pairs. It's primarily about a large dipole moment between H and O or F. Lone pairs add a dimension to it, I agree. But if it were primarily about lone pairs, you would see H bonding in ethers and you don't


Okay, sorry, wasn't meaning to overcomplicate things :smile:

Water can H-bond with an ether because an ether can accept a hydrogen bond from water, but, as you say, an ether can't hydrogen bond with another ether because they lack an O-H bond.

Chlorine is also electronegative but doesn't form H-bonds because the lone pairs on Cl aren't ''small'' enough, since it's on the next row of the periodic table and unable to form the same level of connection as those on the first row :yep: /aside
Original post by EierVonSatan
Okay, sorry, wasn't meaning to overcomplicate things :smile:

Water can H-bond with an ether because an ether can accept a hydrogen bond from water, but, as you say, an ether can't hydrogen bond with another ether because they lack an O-H bond.

Chlorine is also electronegative but doesn't form H-bonds because the lone pairs on Cl aren't ''small'' enough, since it's on the next row of the periodic table and unable to form the same level of connection as those on the first row :yep: /aside


no probs. Thanks for adding detail. :smile:

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