Question

Which of the following compounds show intramolecular hydrogen bonding:
A) o-nitrophenol
B) p-nitrophenol
C) phenol
D) Salicyaldehyde
$$1$$) A & B
$$2$$) A & C
$$3$$) A & D
$$4$$) B & C

Answer 1

Hint: We must have to know that phenol is one of the mono substituent benzene compounds. Each mono-substituted moiety has three named positions in the ring. In the ring a nearby mono substituent group is called ortho position, that means two ortho positions are in the ring, because of the left and right side of the substituent group. The alternatively position of the substituent group in the ring is called meta position, here also two meta positions possible in the left and right side of the substituent group. Para position is nothing but directly opposite to the substituent group in the ring. Electrophilic substitutions are attacked in ortho and para position in the ring.

Complete answer:
A) o-nitrophenol
B) p-nitrophenol
C) phenol
D) Salicyaldehyde
o-nitrophenol has strong intramolecular hydrogen bonding.
p- nitrophenol doesn’t have strong intermolecular hydrogen bonding, but it has strong intermolecular hydrogen bonding.
Phenol doesn’t have strong intramolecular hydrogen bonding.
Salicyaldehyde have strong intramolecular hydrogen bonding.
According for the above discussion, we conclude o-nitrophenol and Salicyaldehyde having intramolecular hydrogen bonding.

Hence, option $$3$$ is correct, because o-nitrophenol and Salicyaldehyde (A & D ) have intramolecular hydrogen bonding.

Note:
We have to know that in organic chemistry benzene is one of the important compounds. It is one of the aromatic compounds. The molecular formula of benzene is $${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}$$. Phenol is one of the derivatives of benzene. I simply said phenol is one of the aromatic alcohols. Hydrogen bonds are also one of the important bonds in chemistry. Without hydrogen bonds nothing in the world. There are two types of hydrogen bonds. There are intermolecular hydrogen bonds and intramolecular hydrogen bonds. The hydrogen bond is dependent on the most electronegativity atom in the molecule. o-nitrophenol can be easily steam distilled whereas p- nitrophenol cannot be. This is because of Strong intramolecular hydrogen bonding in o-nitrophenol and strong intermolecular hydrogen bonding in p-nitrophenol.