sir, do I need to remember the datas?? Is there is no tricks for such questions? And sir according to me the electro negativity of oxygen is more than nitrogen so option b should come first if we apply concept.. Pls Sir make me clear it..
Hydrogen bonding is special type of dipole-dipole interaction between molecules, not a covalent bond to hydrogen atom
Option A: O-H--------N-
In above case, Oxygen is more electronegative and attached to hydrogen. Therefore the electron pair between O-H bond will be shifted towards the oxygen it bears partial negative charge hence hydrogen become electron deficient and bears partial positive charge.
Then this partially positive hydrogen is attracted to another atom i.e. N which is less electronegative than oxygen,
Therefore the bond strength of hydrogen bond between Hydrogen and nitrogen will be strong
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