Alcohols, Phenols and Ethers: Preparation Method: Hydrolysis of Haloalkanes (For CBSE, ICSE, IAS, NET, NRA 2022)

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Preparation Method

Hydrolysis of Haloalkanes

Haloalkanes can be converted to corresponding alcohols using aqueous sodium or potassium hydroxide or water as nucleophiles.

Hydrolysis of Haloalkanes

From Hydration of Alkenes

Hydration means addition of water molecule. In case of alkenes, hydration is the addition of and across the double bond to give alcohols.

Alkenes can be hydrated by the following methods:

Acid-Catalysed Hydration

Alkenes can be hydrated to yield alcohols in the presence of acid catalysts.

Oxymercuration-Demarcation

Alkenes react with mercury (II) acetate, i.e.. mercuric acetate in aqueous tetrahydrofuran (THF) solvent to give hydroxyalkyl mercury compounds which are reduced to alcohols by sodium borohydride.

Step 1: Oxymercuration

Oxymercuration - Demarcation

Step 2: Demarcation

Oxymercuration - Demarcation

Hydroboration – Oxidation

When an alkene reacts with (a boron hydride) in THF solution, an organoborane is obtained.

Hydroboration - Oxidation

Since has three hydrogens, above addition can occur three times to give trialkyl borane . This is shown below for propene.

Hydroboration - Oxidation

Reduction of Carbonyl Compounds

Carbonyl compounds such as aldehydes, ketones, carboxylic acids and esters can be reduced to alcohols.

Reduction of Carbonyl Compounds

Lithium aluminum hydride reduces all of the above classes of compounds while sodium borohydride reduces only aldehydes and ketones and does not reduce carboxylic acids and esters.

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