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why can't H make a hydrogen bond with carbon? I understand that hydrogen bonds can be made with N, O, and F because they're extremely electronegative and so they pull electrons towards them (making it partially negative), but then the difference in electronegativity of carbon and hydrogen is not significant enough to make a hydrogen bond. what is the threshold for the electronegativities to be different enough to make a hydrogen bond?
I think it's important to keep in mind that hydrogen bonding and covalent bonding are not the same thing. Covalent bonds are intramolecular forces while hydrogen bonding is an intermolecular force. Hydrogen can still covalently bond to carbon within a molecule. However, outside the molecule, hydrogen bonding can only occur between hydrogen that has already covalently bonded to a highly electronegative atom, such as Nitrogen, Oxygen, or Fluorine (Chlorine has a similar electronegativity to Nitrogen but the atom itself is too large to form a hydrogen bond) and another highly electronegative atom, again Nitrogen, Oxygen, and Fluorine. Hydrogen bonding itself is the electrostatic attraction between the covalently bonded hydrogen and the highly electronegative atom as a result of the difference in their electronegativities. For example, the Hydrogen in one water molecule is already covalently bonded to Oxygen within the same molecule. When that Hydrogen is in the presence of Oxygen of another water molecule, hydrogen bonding will occur.
Hi! I believe the reason hydrogen can't make a hydrogen bond with carbon is due to electronegative and bond length. Carbon and hydrogen have a very small difference in electronegativities which makes the bond non-polar. H makes hydrogen bonds with N, O, and F due to their high difference in electronegativities.
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