Chemistry Class 12 NCERT Solutions: Chapter 11 Alcohols Phenols and Ethers Part 11

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Q: 32. Show how would you synthesize the following alcohols from appropriate alkenes?

(i)

Q 32 i The Alcohols from Appropriate Alkenes

Q 32 I the Alcohols from Appropriate Alkenes

(ii)

Q 32 ii The Alcohols from Appropriate Alkenes

Q 32 II the Alcohols from Appropriate Alkenes

(iii)

Q 32 iii The Alcohols from Appropriate Alkenes

Q 32 III the Alcohols from Appropriate Alkenes

(iv)

Q 32 iv The Alcohols from Appropriate Alkenes

Q 32 IV the Alcohols from Appropriate Alkenes

Answer:

The given alcohols can be synthesized by applying Markovnikov’s rule of acid-catalyze hydration of appropriate alkenes.

(i)

Q 32 i Ans The Markovnikov’s Rule of Acid-Catalyze Hydration …

Q 32 I Ans the Markovnikov’S Rule of Acid-Catalyze Hydration

(ii)

Q 32 ii Ans The Markovnikov’s Rule of Acid-Catalyze Hydratio …

Q 32 II Ans the Markovnikov’S Rule of Acid-Catalyze Hydratio …

(iii)

Q 32 iii Ans The Markovnikov’s Rule of Acid-Catalyze Hydrati …

Q 32 III Ans the Markovnikov’S Rule of Acid-Catalyze Hydrati …

Acid-catalyzed hydration of pent-2-ene also produces pentan-2-ol but along with pentan-3-ol.

Q 32 iii 1 Ans The Markovnikov’s Rule of Acid-Catalyze Hydra …

Q 32 III 1 Ans Markovnikov’S Rule of Acid-Catalyze Hydration

Thus, the first reaction is preferred over the second one to get pentan-2-ol.

Q 32 iii 2 Ans The Markovnikov’s Rule of Acid-Catalyze Hydra …

Q 32 III 2 Ans Markovnikov Rule of Acid-Catalyze Hydration

Q: 33. When 3-methylbutan-2-ol is treated with , the following reaction takes place:

Q 33 3-Methylbutan-2-ol is Treated with HBr

Q 33 3-Methylbutan-2-Ol is Treated with HBr

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.

Answer

The mechanism of the given reaction involves the following steps:

Step 1: Protonation

Q 33 1 Protonation

Q 33 1 Protonation

Step 2: Formation of carbocation by the elimination of a water molecule

Q 33 2 Formation of 2° Carbocation by the Elimination of a W …

Q 33 2 2 Carbocation by the Elimination of a Water Molecule

Step 3: Re-arrangement by the hydride-ion shift

Q 33 3 Re-Arrangement by the Hydride-ion Shift

Q 33 3 Re-Arrangement by the Hydride-Ion Shift

Step 4: Nucleophilic attack

Q 33 4 Nucleophilic Attack

Q 33 4 Nucleophilic Attack

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