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Is a hydrogen bond considered to be a Van der Waals force?

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2 Answers 2

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According to the IUPAC gold book a van der Waals force is:

The attractive or repulsive forces between molecular entities (or between groups within the same molecular entity) other than those due to bond formation or to the electrostatic interaction of ions or of ionic groups with one another or with neutral molecules. The term includes: dipole–dipole, dipole-induced dipole and London (instantaneous induced dipole-induced dipole) forces.

Hydrogen bonding is a type of dipole-dipole interaction, so it would fit the definition of a van der Waals force.

The way I think of it is: van der Waals forces are anything that make a gas non-ideal, since that's how they were originally discovered and defined.

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    $\begingroup$ But doesn't hydrogen bonding contain a rather sizable covalent component which would mean it doesn't fall under the IUPAC definition? $\endgroup$
    – Philipp
    Commented Jan 25, 2015 at 14:08
  • $\begingroup$ @Phillip - Sure, you could argue that. I guess it would depend on if you consider the covalent nature or the ionic nature more significant. Traditionally, it is classified as a particularly strong dipole-dipole interaction, which makes sense because we normally talk about van der Waals forces in the context of gases. $\endgroup$
    – thomij
    Commented Jan 25, 2015 at 15:23
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    $\begingroup$ The provisional IUPAC recommendation for the definition of hydrogen bond requires "evidence of bond formation" and refers to "partial covalent bond formation". This would seem to exclude the "other than those due to bond formation" requirement of the van der Waals definition. media.iupac.org/reports/provisional/abstract11/arunan_prs.pdf $\endgroup$
    – DavePhD
    Commented Jan 25, 2015 at 23:19
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    $\begingroup$ I agree with @DavePhD and the source he cited (maybe make it an answer for a more permanent record?). The goldbook however recommends, to regard an Hydrogen bond as an "electrostatic interaction", which would make it fall under the mentioned vdW description. This is one of those topics, where a pure classification is not possible - in some cases the covalent character would outweigh the ionic and in some cases it would be the other way around. $\endgroup$ Commented Jan 29, 2015 at 2:37
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    $\begingroup$ @Martin, that's why I look at it in the context of gases, which is really the only context in which it makes sense to talk about van der Waals forces as a group. In any other context, the different interactions are treated separately. $\endgroup$
    – thomij
    Commented Jan 29, 2015 at 5:51
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There are two definitions of a hydrogen bond in the Gold Book: hydrogen bond (1994) and hydrogen bond (1999). The later stresses both the covalent bond nature and the electrostatic interaction component, which both can make it fall outside of the van der Waals forces as of the 1994 definition.

EDIT: Answer edited following the remarks made by @tomij below. See also the interesting discussion below his answer as to the context (historical and experimental) leading to the introduction of the notion of van der Waals forces/interactions.

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    $\begingroup$ The later definition is not saying hydrogen bonds are covalent, it is saying that a covalent bond between H and an electronegative atom results in electrostatic interactions between the H and a different electronegative atom. Also, the van der Waals definition is excluding charge interactions between ions, but H and the other bonding atom are not ions. It also says "The term is sometimes used loosely for the totality of nonspecific attractive or repulsive intermolecular forces," which would include hydrogen bonding. It also mentions dipole-dipole, which includes hydrogen bonding. $\endgroup$
    – thomij
    Commented Jan 27, 2023 at 22:30
  • $\begingroup$ @thomij In the latter definition, it says "forms an additional weaker bond" and then "[the] energy of hydrogen bonds [...] results from the electrostatic interaction and also from the orbital interaction [between] the hydrogen donor [and] the hydrogen acceptor molecule." Isn't orbital interaction a feature of covalent bonds? Also, hydrogen bonds then form dipolar bonds and result from coordination which also involves covalent bonding... In acides/bases isn't the link at least partially covalent? $\endgroup$
    – The Quark
    Commented Feb 4, 2023 at 12:55
  • $\begingroup$ It is true that hydrogen bonds are partially covalent, which is why they are distinguished from other dipole-dipole interactions. However, they are also not fully covalent - which is why they are distinguished from fully covalent bonds as well. Historically van der Waals forces were any force that accounted for non-ideal gas behavior of real gases. I think it's fair to say that hydrogen bonding is one of those forces. I also think it's fair to say that because the other forces have little to no covalent character, hydrogen bonding should be thought of as different from them. $\endgroup$
    – thomij
    Commented Feb 6, 2023 at 18:36
  • $\begingroup$ @thomij Indeed, the historical perspective is quite enlightening. I've made a limited bibliographic survey of recent publications and although some authors argue that HBs and vdW interactions are distinct, either their argument is quantitative, thus making the distinction arbitrary, or they assign a priori attributes to vdW interactions chosen so as to set them apart from HBs, but I doubt that those attributes were stated by van der Waals himself (I need to read his original work still). But so now I tend to think that HBs should actually be considered to belong to the set of vdW interactions. $\endgroup$
    – The Quark
    Commented Feb 9, 2023 at 18:21

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