Question

We learn that an acetylide ion can serve as a nucleophile in an SN2 reaction. How is the acetylide ion formed?

a) Treatment of acetylene with an acid
b) Treatment of acetylene with a strong base
c) Exposure of acetylene to UV radiation
d) Oxidation of acetylene with a metal catalyst

Answer 1

The acetylide ion is generated by treating acetylene with a strong base, which removes a proton, allowing it to then act as a nucleophile in SN2 reactions.

Step-by-step explanation:

An acetylide ion is formed by the treatment of acetylene with a strong base. This base abstracts a proton from the terminal alkyne, like acetylene, which is relatively acidic due to the sp-hybridization of the carbon atom bonded to the hydrogen. The acetylide ion, being a strong nucleophile, can then participate in SN2 reactions. It is important to note that while the reagent is a nucleophile in SN2 reactions, it can also act as a base in E2 reactions. Thus, the choice of base and reaction conditions significantly affect whether an SN2 or E2 reaction mechanism will predominate.