Organic Chemistry Synthesis Reactions - Examples and Practice Problems - Retrosynthesis

TL;DR

Learn how to perform various synthesis reactions with alkynes using sodium amide, alkyl halide, sodium metal with liquid ammonia, and other reagents.

Transcript

in this video we're going to focus on synthesis reactions reactions associated with alkynes gradient reagents and we're going to cover some other examples but let's begin so this is acetylene which is basically a two carbon alkyne and what we're going to do first is we're going to add sodium amide to it and a nh2 the nh2 ion is a very strong base i... Read More

Key Insights

• 💁 Sodium amide can remove hydrogen from alkynes, forming acetylide ions that participate in carbon-carbon bond formation.
• 💁 Alkyl halides can react with acetylide ions to form new carbon-carbon bonds through nucleophilic substitution (SN2).
• 🤘 Reduction of alkynes to alkenes can be achieved using sodium metal and liquid ammonia.
• 💁 Grignard reagents, such as methylmagnesium bromide, can react with alkoxide ions to form carbon-carbon bonds.
• ❓ Acid chlorides can be converted to ketones using the Gilman reagent or to aldehydes using DIBAL, with nucleophilic addition and elimination reactions.
• 👻 The Wittig reaction allows for the conversion of ketones into alkenes by reacting them with phosphorus ylides.

Questions & Answers

Q: How is an acetylide ion formed from an alkyne?

The strong base sodium amide removes a hydrogen from the alkyne, creating a negatively-charged carbon known as an acetylide ion, which is highly nucleophilic.

Q: How can you add four carbons to an alkyne and convert it into an alkene?

First, sodium amide removes a hydrogen from the alkyne. Then, an alkyl halide containing four carbons is added. Finally, sodium metal with liquid ammonia reduces the alkyne, resulting in a four-carbon alkene.

Q: How can you convert an acid chloride into a ketone or aldehyde?

By using the Gilman reagent, the acid chloride can be reduced to a ketone. To stop at the aldehyde level, the reagent DIBAL is used. These reactions involve nucleophilic attack and subsequent elimination.

Q: What is the Wittig reaction used for?

The Wittig reaction is utilized to convert ketones into alkenes. It involves reacting a ketone with a phosphorus ylide, which replaces the carbonyl group with a double bond.

Summary & Key Takeaways

• Sodium amide is added to an alkyne, creating an acetylide ion that can react with an alkyl halide, resulting in a carbon-carbon bond formation.

• To add four carbons to an alkyne, sodium amide removes a hydrogen, followed by the addition of a four-carbon alkyl halide. The alkyne is then reduced to an alkene using sodium metal with liquid ammonia.

• The Grignard reagent methylmagnesium bromide can react with an alkoxide ion, forming a carbon-carbon bond and resulting in the addition of a methyl group.

• Different reagents can be used to convert acid chlorides into ketones or aldehydes, such as the Gilman reagent or DIBAL.

• The Wittig reaction can convert ketones into alkenes by adding the corresponding ylides.