Protecting Groups

The video tutorial by Professor Dave explains the SN2 reaction and the challenges posed by methoxide due to its dual role as a nucleophile and a strong base. It introduces the concept of protecting groups, specifically using TBDMS to shield hydroxyl groups from unwanted reactions, allowing successful SN2 reactions. The tutorial also covers the protection of aldehydes and ketones using acetal formation to prevent unwanted reductions, ensuring selective reactions in synthetic pathways.

Why is methoxide not suitable for SN2 reactions in the presence of a hydroxyl group?

• It forms a stable complex with the substrate.

• It reacts too slowly.

• It is a strong base and causes acid-base reactions.

• It is a weak nucleophile.

What is the role of TBDMS in SN2 reactions?

• It enhances the nucleophilicity of methoxide.

• It protects hydroxyl groups from unwanted reactions.

• It increases the reaction temperature.

• It acts as a catalyst.

How does TBDMS protect the hydroxyl group?

• By forming a covalent bond with the substrate.

• By increasing the acidity of the hydroxyl group.

• By replacing the hydroxyl proton with a silicon atom.

• By forming a stable complex with the nucleophile.

What reagent is used to deprotect the hydroxyl group after an SN2 reaction?

• Sodium borohydride

• Hydrochloric acid

• Lithium aluminum hydride

• Tetrabutyl ammonium fluoride (TBAF)

What is the purpose of using ethane diol in protecting ketones?

• To increase the electrophilicity of the ketone.

• To form an acetal that prevents unwanted reductions.

• To enhance the nucleophilicity of the ketone.

• To act as a reducing agent.

Why is the acetal formation useful in protecting ketones?

• It makes the ketone more reactive.

• It reduces the electrophilicity of the carbonyl carbon.

• It increases the acidity of the ketone.

• It enhances the nucleophilicity of the ketone.

What happens to the electrophilicity of a carbonyl carbon when it forms an acetal?

• It increases significantly.

• It becomes more acidic.

• It remains unchanged.

• It decreases significantly.