A chemist is planning to synthesize 3 -octyne by adding 1...

Name: Problem 53, Chapter 7: Organic Chemistry
Uploaded: 2020-07-27T18:06:45-08:00
Duration: 1 min 31 s
Channel: Madeline Currie
Description: A chemist is planning to synthesize 3 -octyne by adding 1 -bromobutane to the product obtained from the reaction of 1-butyne with sodium amide. Unfortunately, however, he forgot to order 1-butyne. How else can he prepare 3-octyne?

A chemist is planning to synthesize 3 -octyne by adding 1 -bromobutane to the product obtained from the reaction of 1-butyne with sodium amide. Unfortunately, however, he forgot to order 1-butyne. How else can he prepare 3-octyne?

Key Concepts

Acetylide Anion Formation and Alkynylation

Terminal alkynes can be deprotonated by strong bases to form acetylide anions, which are nucleophilic and can undergo SN2 alkylation with alkyl halides. This reaction is a key method for creating carbon–carbon bonds and is widely used in the synthesis of unsymmetrical internal alkynes by attaching different alkyl groups to the acetylide ion.

Double Elimination Reactions for Alkyne Synthesis

An important method for synthesizing terminal alkynes involves the double elimination of vicinal or geminal dihalides. In this process, a dihalogenated alkane is treated with a strong base to remove two molecules of hydrogen halide, resulting in the formation of a triple bond. This approach provides an alternative route to prepare the necessary terminal alkynes for further functionalization.

Retrosynthetic Analysis for Unsymmetrical Internal Alkynes

Retrosynthetic analysis involves breaking down a target molecule into simpler precursor structures. In the context of unsymmetrical internal alkyne synthesis, the target is dissected into two components: a terminal alkyne (or an acetylide anion derived therefrom) and an alkyl halide. This analysis guides the design of a synthetic route by emphasizing alternative precursor routes such as in situ generation of the terminal alkyne via elimination reactions when the ideal starting alkyne is not available.

Transcript

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