# What are the prerequisites in hydrogen bonding?

I know when a hydrogen bond is, but - can hydrogen bonds only occur between two molecules containing hydrogen? Or, only one of the molecules should contain hydrogen and the other one may not contain hydrogen, but should have a large electronegative difference between two of its sides?

Actually, theoretically speaking hydrogen bond is the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge. A hydrogen bond may occur between $\ce{H-O}$, $\ce{H-N}$, $\ce{H-F}$ (first two are more common). Apart from that, these hydrogen-bond attractions can occur between molecules (intermolecular) or within different parts of a single molecule (intramolecular)

See also the Wikipedia article about hydrogen bonding A hydrogen atom attached to a relatively electronegative atom will play the role of the hydrogen bond donor An electronegative atom such as fluorine, oxygen, or nitrogen will be the hydrogen bond acceptor, irrespective of whether it is bonded to a hydrogen atom or not. An example of a hydrogen bond acceptor that does not have a hydrogen atom bonded to it is the oxygen atom in diethyl ether.

http://chemwiki.ucdavis.edu/@api/deki/files/4680/image115.png?revision=1

• Hi Martin, as I said, I know th definition of a hydrogen bond. My question is- should hydrogen be present in both molecules participating in a hydrogen bond or not ? If not , will you please give me an example ? THanks a lot! – NotAChemist Jun 22 '15 at 7:54
• actually hydrogen bond is bond between one atom which must be hydrogen and other one can be oygen, nitrogen or fluorine it is not necessary to have hydrogen in both molecules involved in bonding one molecule must have hydogen( that one is proton donor) here is example:google.co.in/… – user17052 Jun 22 '15 at 8:00