Alkyne Synthesis by Double Dehydrohalogenation

Professor Dave explains the synthesis of alkynes using E2 reactions, focusing on vicinal and geminal dihalides. He discusses the use of strong bases like sodamide and the importance of excess base in reactions with geminal dihalides. The video also covers the formation of acetylide ions and their applications in further reactions, such as SN2, to create fully substituted alkynes.

What type of reaction is primarily used in the synthesis of alkynes from vicinal dihalides?

• Substitution reaction

• SN1 reaction

• E2 reaction

• Hydration reaction

Why is sodamide considered an extremely strong base in the context of dehydrohalogenation?

• Its conjugate acid is a strong acid.

• It has a high molecular weight.

• It reacts slowly with halogens.

• Its conjugate acid is ammonia, which is also a base.

What is a key difference between vicinal and geminal dihalides?

• Vicinal dihalides have halogens on adjacent carbons.

• Geminal dihalides are more reactive than vicinal dihalides.

• Vicinal dihalides have halogens on the same carbon.

• Geminal dihalides have halogens on adjacent carbons.

Why is excess base required when working with geminal dihalides?

• To increase the reaction temperature.

• To ensure complete dehydrohalogenation and avoid mixtures.

• To decrease the reaction time.

• To prevent the formation of side products.

What is the role of the acetylide ion in SN2 reactions?

• It is a leaving group.

• It serves as a nucleophile.

• It acts as a catalyst.

• It stabilizes the reaction intermediate.

What is the shape of the acetylide ion that makes it a good nucleophile?

• Tetrahedral

• Bent

• Planar

• Linear

What can be achieved by performing an SN2 reaction with an acetylide ion?

• Formation of a fully substituted alkyne

• Formation of a geminal dihalide

• Formation of a terminal alkyne

• Formation of a vicinal dihalide