Identify the reagents used for the following conversion
- A = LiAlH4, B = NaOH(aq), C = NH2–NH2/KOH, ethylene glycol
- A = LiAlH4, B = NaOH(alc), C =Zn/HCl
- A = DIBAL-H, B= NaOH(aq), C = NH2–NH2/KOH, ethylene glycol
- A = DIBAL-H, B = NaOH(alc), C = Zn/HCl
The Correct Option is D
Approach Solution - 1
To identify the reagents for the given chemical conversion, let's analyze each step:
- Step A: The first conversion involves the reduction of an ester to an aldehyde.
- DIBAL-H (Diisobutylaluminium hydride) is a reagent known for its ability to reduce esters to aldehydes specifically under controlled conditions (low temperatures).
- LiAlH4 (Lithium Aluminium Hydride) is a strong reducing agent that typically reduces esters all the way to alcohols, which doesn't match the reaction type observed.
- Step B: The conversion from an alcohol to an alkene involves a dehydration step.
- NaOH (alc) (Alcoholic sodium hydroxide) is often used in elimination reactions to form alkenes through dehydration of alcohols.
- NaOH (aq) is typically involved in substitution rather than elimination.
- Step C: The conversion from an intermediate to an alkene involves reduction and removal of an oxygen group.
- Zn/HCl is a known reducing system that can be used for converting ketones or aldehydes by reducing them, often used in the Clemmensen reduction which removes carbonyl groups.
- NH2–NH2/KOH, ethylene glycol (Wolff-Kishner reduction) is another reduction method that converts ketones to alkanes, but typically under different conditions and solvents.
Conclusion: The correct reagents are:
- A = DIBAL-H
- B = NaOH (alc)
- C = Zn/HCl
Thus, the correct answer is A = DIBAL-H, B = NaOH(alc), C = Zn/HCl.
Approach Solution -2
In this reaction, the following steps occur:
Step A: Reduction of ester to aldehyde using DIBAL-H (Diisobutylaluminum hydride), a selective reducing agent that reduces esters to aldehydes without affecting other functional groups.
Step B: Aldol condensation, which involves the formation of an intramolecular aldol product. This reaction is catalyzed by NaOH (alc) (sodium hydroxide in alcoholic solution).
Step C: Reduction of the product to alcohol using Zn/HCl in the Clemmensen reduction method, which reduces aldehydes to alcohols.
Thus, the correct reagents are 4, which corresponds to:
- \( A = \text{DIBAL-H} \)
- \( B = \text{NaOH (alc)} \)
- \( C = \text{Zn/HCl} \).
The Correct Answer is: A = DIBAL-H, B = NaOH(alc), C = Zn/HCl
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