Question

Alkyne anions react with the carbonyl groups of aldehydes and ketones to form alkynyl alcohols, as illustrated by the following sequence.

Short answer

Answer: The product formed in the reaction between an alkyne anion and a carbonyl compound is an alkynyl alcohol.

Step-by-step solution

Identify the reactants and products

First, let us recognize the reactants involved in the reaction - an alkyne anion, which is a negatively charged alkyne species, and a carbonyl compound (either an aldehyde or a ketone). The product of this reaction is an alkynyl alcohol.

Understand the reaction mechanism

The reaction mechanism involves a nucleophilic attack of the alkyne anion on the carbonyl carbon of the aldehyde or ketone. This results in the formation of an alkoxide intermediate, which then undergoes protonation to form the final alkynyl alcohol product.

Write down the nucleophilic attack

The alkyne anion, being a nucleophile, attacks the electrophilic carbonyl carbon of the aldehyde or ketone, forming a new carbon-carbon bond and pushing the carbonyl's pi electrons onto the oxygen atom. This results in the formation of an alkoxide intermediate: RC≡C^{-} + R'CHO → RC≡CR'O^{-}

Protonate the alkoxide intermediate

The negatively charged oxygen in the alkoxide intermediate abstracts a proton from a suitable proton source (such as water or an alcohol): RC≡CR'O^{-} + H^{+} → RC≡CR'OH

Write the final reaction

Combining the steps in the mechanism, we can now write the overall reaction: RC≡C^{-} + R'CHO + H^{+} → RC≡CR'OH This is the general reaction between an alkyne anion and a carbonyl compound (either an aldehyde or a ketone), resulting in the formation of an alkynyl alcohol.