Hydrogen bonding is an electrostatic attraction between covalently bonded hydrogen atom of one molecular with highly electronegative atom (N or F or O) of the same molecular or another molecule. or another molecular .It is of two types -(i) Intermolecular hydrogen bonding where molecular association is caused due to interaction of $H-atom$ of one molecular and N or F or 0-atoms of different molecules. (ii) Intramolecular hydrogen bonding where hydrogen bonding occurs between H atom and N or F or O-atom of the same molecule. Intermolecular hydrogen bonding increases the boiling point of the compound and its solubility in water , whereas intramolecular hydrogen bonding decreases the boiling point of the compound and solubility in water. The maximum possible number of hydrogen bonds in which a water molecule can participate is