Predict the product(s) you would expect from treatment of each compound with (1) dilute, neutral KMnO4 and (2) warm basic KMnO4, then dilute acid.
(b) hex-2-yne

Verified step by step guidance

1. Step 1: Understand the reaction conditions. Neutral KMnO4 (dilute, neutral potassium permanganate) is a mild oxidizing agent that typically adds hydroxyl groups across double or triple bonds, resulting in diols. Warm, basic KMnO4 followed by acidification is a stronger oxidizing agent that cleaves double or triple bonds, producing carboxylic acids or ketones depending on the structure of the starting material.
2. Step 2: Analyze the structure of hex-2-yne. Hex-2-yne is an alkyne with a triple bond between the second and third carbons in a six-carbon chain. Its structure can be written as CH3-C≡C-CH2-CH2-CH3.
3. Step 3: Predict the product with dilute, neutral KMnO4. Neutral KMnO4 will add hydroxyl groups across the triple bond, converting it into a diol. The triple bond will first be oxidized to a double bond, and then hydroxyl groups (-OH) will be added to each carbon of the former triple bond, resulting in a vicinal diol (a compound with two hydroxyl groups on adjacent carbons).
4. Step 4: Predict the product with warm, basic KMnO4 followed by dilute acid. Under these conditions, the triple bond in hex-2-yne will be cleaved completely. Each carbon of the triple bond will be oxidized to a carboxylic acid group (-COOH). Since the triple bond is internal (not terminal), the products will be two carboxylic acids: propanoic acid (CH3-CH2-COOH) from each side of the triple bond.
5. Step 5: Summarize the expected products. For reaction (1) with neutral KMnO4, the product is a vicinal diol. For reaction (2) with warm, basic KMnO4 followed by acid, the products are two molecules of propanoic acid.

Key Concepts

Oxidation Reactions

Oxidation reactions involve the loss of electrons or an increase in oxidation state by a molecule. In organic chemistry, these reactions often lead to the formation of alcohols, ketones, or carboxylic acids. Understanding how different reagents, like KMnO4, act as oxidizing agents is crucial for predicting the products of reactions involving unsaturated hydrocarbons.

KMnO4 as an Oxidizing Agent

Potassium permanganate (KMnO4) is a strong oxidizing agent used in organic synthesis. In dilute, neutral conditions, it typically oxidizes alkenes and alkynes to form diols, while in warm basic conditions, it can cleave double or triple bonds, leading to the formation of carboxylic acids or ketones. The specific conditions dictate the extent and type of oxidation that occurs.

Alkyne Reactivity

Alkynes, such as hex-2-yne, are hydrocarbons characterized by at least one triple bond. Their reactivity is influenced by the presence of this triple bond, which can undergo various reactions, including oxidation. Understanding the structure and reactivity of alkynes is essential for predicting the outcomes of reactions with oxidizing agents like KMnO4.