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Approaching a Synthesis Problem - Exercise 110 (e) and (f)

Exercise 12.10 (e) and (f) - Approaching a Synthesis Problem

Exercise 12.10 (e) and (f) - Approaching a Synthesis Problem

Introduction

This video continues with Exercise 12.10, focusing on multi-step synthesis problems in organic chemistry. The exercises aim to build skills in planning and executing complex synthetic routes by analyzing structural changes and applying appropriate reactions.

Main Points

- Counting Carbons:

    - The starting material has four carbons with a methyl group, while the product has six carbons, indicating the need to add two carbons.
    - Use a terminal alkyne and sodium amide to create a nucleophile.
    - Identify whether the starting material should be the terminal alkyne or the alkyl halide.

- Reactive Part of the Molecule:

    - The reactive part of the product is between carbons five and six, suggesting that carbons five and six should be introduced as a separate molecule.
    - Turn the starting material into an alkyl halide with a leaving group on carbon four.

- Addition and Elimination Reactions:

    - Perform anti-Markovnikov addition of HBr with peroxides to place the bromine correctly.
    - Use a bulky base like potassium tert-butoxide for elimination to form the less substituted alkene (Hofmann product).
    - Perform another anti-Markovnikov addition of HBr with peroxides to get the final alkyl halide.

- Final Steps:

    - React the terminal alkyne with sodium amide to form the nucleophile.
    - Conduct the SN2 reaction with the alkyl halide.
    - Perform a water wash to stabilize the product.

- Counting Carbons:

    - The starting material has two carbons attached to a cyclohexane ring, while the product has only one, indicating a carbon removal.
    - Use ozonolysis to achieve this transformation.

- Forming the Alkene:

    - Identify the alkene needed for ozonolysis.
    - Perform elimination to create the required alkene.

- Ozonolysis:

    - Use TSCl and pyridine to turn the OH group into a good leaving group.
    - Use potassium tert-butoxide to form the Hofmann product (less substituted alkene).
    - Perform ozonolysis with ozone and dimethyl sulfide to achieve the final product.
Examples/Evidence

- Detailed mechanisms for each reaction step, including nucleophilic attack, elimination reactions, and ozonolysis.

- Emphasis on controlling the position of reactive parts of the molecule through Markovnikov and anti-Markovnikov additions, and using appropriate bases for elimination.

Additional Insights

- Encouragement to explore multiple pathways and understand that there can be more than one correct synthesis route.

- Importance of trial and error in the process of designing synthesis routes.

Conclusion

The video provides a comprehensive approach to solving multi-step synthesis problems by breaking down each transformation into manageable steps. It emphasizes the importance of counting carbons, understanding the reactivity of intermediates, and choosing appropriate reagents and conditions for each step.

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