Q35 E - Organic Chemistry (Mcmurry)

Question

Question: Identify the reagents a–c in the following scheme:

Step-by-Step Solution

Answer

The reagents a, b, c can be given as:

Reagent a -  NaNH₂, NH₃ and  CH₃CH₂Br

Reagent b-  H₂ and Lindlar’s catalyst

Reagent c-   CH₂I₂ and Zn(Cu)

Step 1: Reagents used for the conversion of alkynes to other compounds

Alkynes can be reduced to cis alkenes by treating them with hydrogen in the presence of Lindlar’s catalyst. They can also be converted to higher alkynes by treating them with NaNH₂  , ammonia and the required alkyl halide.

Step 2: Identifying the reagents for the following conversion

 The first reactant, 3-methylbut-1-yne reacts with reagent a, NaNH₂, NH₃  and CH₃CH₂Br and gets converted to 2-methylhex-3-yne. This product reacts with reagent b, H₂  and Lindlar’s catalyst to form the product (Z)-2-methylhex-3-ene. This further reacts with reagent c, CH₂I₂  and Zn(Cu) to form the product (1S,2S)-1-ethyl-2-isopropylcyclopropane.

The overall reaction can be given as:

Reagents involved in the reaction