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I was looking for an accurate definition of halogen bonding. I was able to find quite a few good ones, but none of them would explain if a X---H intermolecular interaction would count as a form of halogen bonding. Where X is any halogen and H is a hydrogen from another molecule. Does this count as halogen or hydrogen bonding? Or maybe as both?

Thank you,

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I would say no, it is only a hydrogen bond, not a halogen bond.

To be a halogen bond, the halogen atom must accept electron density from the other member of the bond. If the other member of the bond is a hydrogen atom bonded to a more electronegative element, I don't see have the halogen atom could be an acceptor of electron density.

If you can get access see "Halogen Versus Hydrogen" Science Vol. 321 no. 5891 pp. 918-919. Footnote 7 there explains: "A halogen bonding donor is a species that contains an electrophilic halogen that can become a member of a halogen bond. In the literature on halogen bonding, the reader should be alert to how the words 'donor' and 'acceptor' are used. In a complex RX---B, RX is the halogen bond donor but the electron acceptor (Lewis acid); B is the electron donor and halogen bond acceptor (Lewis base)."

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  • $\begingroup$ Thanks for your answer DavePhD. I completely agreed with what you said at the first glance. But later, I started thinking of the interaction in details. The nucleus of the halogen (chlorine for example) is much stronger at withdrawing electrons than the hydrogen nucleus. That means the chlorine atom is actually accepting the hydrogen's electron (and that's why causes their interaction at small distances). Thinking in this way suggests it is a halogen bond. Unless I have missed something during those deep thoughts! -oh and thanks for the reference btw- :) $\endgroup$ – Error404 Dec 17 '14 at 14:34
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    $\begingroup$ If you look at the definition of hydrogen bond quoted in my answer here: chemistry.stackexchange.com/questions/21773/… it requires that the acceptor of the hydrogen bond is "an electron rich region", which directly contradicts the requirement of a halogen bond, that the halogen act electrophilicly. $\endgroup$ – DavePhD Dec 17 '14 at 14:51
  • $\begingroup$ Yes I think I got what you are saying. All clear now! Appreciated. $\endgroup$ – Error404 Dec 17 '14 at 14:55

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