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JEE Main 2024 Question Paper With Solutions PDF

Physical and Chemical Properties of Phenols - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:35 AM | #JEE Main

Quick Facts

  • Reimer-Tiemann and Kolbe's Schmidt Reactions is considered one the most difficult concept.

  • Reaction of Phenols with dil. HNO3 is considered one of the most asked concept.

  • 67 Questions around this concept.

Solve by difficulty

Reaction of trans-2-phenyl­-1­-bromocyclopentane on reaction with alcoholic \mathrm{KOH} produces

Reaction of phenol with chloroform in presence of dilute sodium hydroxide finally introduces which one of the following functional group?

Which of the following will not be soluble in sodium hydrogen carbonate?

An organic compound 'A' with emperical formula \mathrm{C_{6}H_{6}O} gives sooty flame on burning. Its reaction with bromine solution in low polarity solvent results in high yield of B. B is

Phenolic group can be identified by a positive :

Which one of the following class of compounds is obtained by polymerization of acetylene ?

Bakelite is obtained from phenol by reaction with

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Salicylaldehyde is synthesized from phenol, when reacted with

Concepts Covered - 6

Properties of Phenols
  1. Phenols are either colourless liquids or white crystalline solids.
  2. Phenols are soluble in hot water.
  3. The boiling points of phenols are much higher than the corresponding aromatic hydrocarbons and the haloarenes.
  4. Phenols have anti-fungal and anti-bacterial properties. Thus used as disinfectants and antiseptics.
  5. Phenols are poisonous in nature but act as antiseptic and disinfectant.
Reactions due to (-OH) group

Reaction with zinc dust: When phenol is distilled with zinc dust, benzene is obtained. The reaction occurs as follows:

Reaction with NH3Phenol reacts with ammonia in presence of anhydrous zinc chloride at 573K or (NH4)2SO3-NH3 at 423K to form aniline. This conversion of phenol into aniline is called Bucherer reaction.

Reaction with FeCl3Phenol gives violet colouration with ferric chloride solution sue to the formation of a coloured iron complex, which is a characteristic to the existence of keto-enol tautomerism in phenols.

Reimer-Tiemann and Kolbe's Schmidt Reactions

Riemer-Tiemann Reaction
Phenols for aromatic compounds containing EDG when refluxed with CHCl3 and alkali yield o- and p- hydroxybenzaldehyde. The ortho product is the predominant product. It is an electrophilic substitution on PhO- ion. The electrophile is dichlorocarbene (:CCl2) which contains a C with only six electrons.

Mechanism
The mechanism of this reaction follows the following steps.

For example,

Koble-Schmitt Reaction
Phenol when heated at(390-410K) under pressure with CO2 and alkali gives salicylic acid after acidification in addition to some amount of p-isomer.

Mechanism 

For example,

Claisen's Rearrangement

On heating aryl allyl or alkyl allyl ethers in inert solvent, the allyl group migrates from the ortho position to the ring, preferable at ortho position, but para if the ortho position is blocked.

Mechanism
The mechanism of this reaction occurs in three following steps:

  1. Enolate formation
  2. Nucleophilic attack

     
  3. Removing of leaving group
Reaction with Conc. HNO3, Phthalic Anhydride

Nitration
Anisole reacts with a mixture of concentrated sulphuric and nitric acids to yield a mixture of ortho and para nitroanisole. The reaction occurs as follows.

Phthalic Anhydride
Phenol couples with phthalic anhydride in presence of conc. H2SO4 to form phenolphthalein which is used as an indicator. The reaction occurs as follows.

Reaction of Phenols with dil. HNO3

With dilute nitric acid at low temperature (298 K), phenol yields a mixture of ortho and para nitrophenols. The reaction occurs as follows.


The ortho and para isomers can be separated by steam distillation. o-Nitrophenol is steam volatile due to intramolecular hydrogen bonding while p-nitrophenol is less volatile due to intermolecular hydrogen bonding which causes the association of molecules. 

Study it with Videos

Properties of Phenols
Reactions due to (-OH) group
Reimer-Tiemann and Kolbe's Schmidt Reactions

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