Question

Which molecule has the strongest hydrogen bonding?
A.${C_6}{H_5}OH$
B.$C{H_3}OH$
C.$C{H_3}N{H_2}$
D.$HCHO$

Answer 1

The hydrogen bond is formed when a hydrogen atom makes a bond with more electronegative atoms such as nitrogen $(N)$ , fluorine $(F)$ , oxygen $(O)$ . In intermolecular bonding, the bond is formed between the hydrogen atoms of one molecule with the electronegative atom of the other similar molecule.

Complete answer:
Hydrogen bonding is important to know for a particular molecule because it defines its capability to dissolve in water. Therefore, the molecules that can form a hydrogen bond are soluble in water and those that cannot form hydrogen bonds are weakly or not soluble in water. The stronger the hydrogen bond, the more the solubility.
So , from above discussion we can say that among the given options , the molecule with the highest intermolecular hydrogen bonding is $C{H_3}N{H_2}$ (Methylamine ) , as it has high electronegative atom nitrogen, $(N)$ , which can easily form bond with then hydrogen atom $(H)$ of water .
Also, $HCHO$ will have very less intermolecular hydrogen bonding because its $(H)$atom is not bound to the electronegative $(O)$ atom.
$C{H_3}OH$ Will have more hydrogen bonding than ${C_6}{H_5}OH$ because ${C_6}{H_5}OH$ consist of bulky group and this will lead to steric hindrance and hence, less hydrogen bonding.
So option C is the correct answer.

Note:
There is a difference between intermolecular and intramolecular hydrogen bonding. As we studied above, intermolecular hydrogen bonding occurs between the same two molecules but in intramolecular hydrogen bonding, bond formation takes place between the $(H)$ atom and the electronegative atom of the same molecule.