Conditions for Hydrogen Bonding

Since hydrogen bond comes into existence as a result of dipole-dipole interactions between the molecules, therefore, following conditions are required for effective hydrogen bonding.

(i) Hydrogen atom should be bonded to a highly electronegative atom such as F, O or N.

Larger the electro negativity of the other atom, greater is the strength of hydrogen bond. For e.g., electronegativities of F, O and N decrease as F > O > N consequently, strengths of H-bonds decrease as F - H …….. F > O - H …….. O > N - H …….. N.

(ii) The size of electronegative atom should be small. If the size of electronegative atom is large, its attractive force with hydrogen atom would be less and consequently, strength of H…. bond will be less. For e.g., N and Cl have same electronegativity but on hydrogen bonds are formed in case of H-Cl because of the larger size of Cl atom.