This question involves identifying the correct product of a chemical reaction where an alkyne undergoes hydroboration-oxidation. The given reactant is a terminal alkyne: $H - C \equiv C - H$ (acetylene).

Step 1: Understand the Reaction Type

The reaction shown is hydroboration-oxidation. For alkynes, this reaction follows Anti-Markovnikov addition and results in the formation of an enol, which immediately tautomerizes to a carbonyl compound (aldehyde or ketone).

Step 2: Apply the Rule to a Terminal Alkyne

For a terminal alkyne (R-C≡C-H), hydroboration-oxidation yields an aldehyde (R-CH₂-CHO). The boron atom adds to the less substituted carbon (the terminal carbon), and oxidation replaces the boron with a hydroxyl group, creating the enol form of an aldehyde.

The specific reaction for acetylene (H-C≡C-H) is: $H - C \equiv C - H \overset{1 . {BH}_{3}, THF 2 . H_{2} O_{2}, {OH}^{-}}{\to} H - C H 2 - C H O$

The product is acetaldehyde, which has the structure: $C H_{3} C H O$ .

Step 3: Match the Product to the Options

We need to find the structure of acetaldehyde among the given image options.

The first image shows a ketone (a carbonyl (C=O) group with two alkyl groups attached).
The second image shows an aldehyde (a carbonyl (C=O) group with one H atom attached). This is the correct structure for acetaldehyde (CH₃CHO).
The third image shows a carboxylic acid (a carbonyl (C=O) group with an -OH attached).
"No reaction" is incorrect because the reaction does proceed.

Final Answer

The correct product (A) is the second option: Structure of acetaldehyde, CH3CHO

Related Topics

Hydroboration-Oxidation of Alkenes
Acidity of Terminal Alkynes
Oxymercuration-Demercuration of Alkynes
Tautomerization (Keto-Enol Tautomerism)

Key Formulae and Theory

General Rule for Alkyne Hydroboration-Oxidation:

$R - C \equiv C - H \overset{1 . {BH}_{3} 2 . H_{2} O_{2}, {OH}^{-}}{\to} R - C H_{2} - C H O$ (An aldehyde)

$R - C \equiv C - R^{'} \overset{1 . {BH}_{3} 2 . H_{2} O_{2}, {OH}^{-}}{\to} R - C O - C^{H} 2 R^{'}$ (A ketone)

Theory: The reaction proceeds via syn addition. The initial product is an enol, which is unstable and undergoes tautomerization to the more stable keto form. This is an anti-Markovnikov addition of water across the triple bond.