When 3-methyl butane-2-ol is treated with HBr, the following reaction takes place:
Give a mechanism for this reaction. (Hint: The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom
When 3-methyl butane-2-ol is treated with HBr, the following reaction takes place:
Give a mechanism for this reaction. (Hint: The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom
Solution and Explanation
The mechanism of the given reaction involves the following steps:
Step 1:Protonation
Step 2:Formation of 2° carbocation by the elimination of a water molecule
Step 3:Re-arrangement by the hydride-ion shift
Step 4:Nucleophilic attack
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Concepts Used:
Preparation - Alcohols, Phenols and Ethers
Alcohols, phenols, and ethers are organic compounds that can be prepared by various methods.
Preparation of Alcohols:
- Direct hydration of alkenes: Alcohols can be prepared by the addition of water to an alkene in the presence of a strong acid catalyst.
- Reduction of carbonyl compounds: Alcohols can be prepared by the reduction of aldehydes, ketones, or carboxylic acids using reducing agents like NaBH4 or LiAlH4.
- Grignard reaction: Alcohols can be prepared by reacting Grignard reagents with carbonyl compounds.
- Hydroboration-oxidation: Alcohols can be prepared by the hydroboration of alkenes followed by oxidation with an oxidizing agent like H2O2.
Preparation of Phenols:
- Hydrolysis of diazonium salts: Phenols can be prepared by the hydrolysis of diazonium salts, which are formed by the reaction of aniline with nitrous acid.
- Oxidation of sulfonic acids: Phenols can be prepared by the oxidation of sulfonic acids using strong oxidizing agents like potassium permanganate or chromic acid.
Preparation of Ethers:
- Williamson synthesis: Ethers can be prepared by the reaction of an alkoxide ion with a primary alkyl halide or tosylate in the presence of a strong base like NaOH or KOH.
- Dehydration of alcohols: Ethers can be prepared by the dehydration of alcohols in the presence of a strong acid catalyst like H2SO4.
In summary, alcohols, phenols, and ethers can be prepared by a variety of methods, including hydration, reduction, Grignard reaction, hydroboration-oxidation, hydrolysis, oxidation, Williamson synthesis, and dehydration. The choice of the method depends on the availability of starting materials, the desired product, and the conditions of the reaction.