Q34 E - Organic Chemistry (Mcmurry)

Question

Propose structures for hydrocarbons that give the following products

on oxidative cleavage by KMnO₄ or O₃ :

Step-by-Step Solution

Answer

Step 1: Oxidative cleavage

Alkynes can be cleaved by oxidizing agents like KMnO₄ or ozone. Triple bonds comprise less reactivity than double bonds and produce low yields.

Step 2: The reactant that gives the products in (a)

(a)The products, heptanoic acid and carbon dioxide are produced when oct-1-yne is treated with KMnO₄ and H₃O⁺. So the hydrocarbon is oct-1-yne. The reaction can be given as: 

Hydrocarbon that produces the products in (a)

Step 3: The reactant that gives the products in (b)

(b)The products benzoic acid and acetic acid are produced when prop-1-yn-1-ylbenzene reacts with KMnO₄ and H₃O⁺. So, the hydrocarbon is prop-1-yn-1-ylbenzene. The reaction can be given as:

Hydrocarbon that produces the products in (b)

Step 4: The reactant that gives the products in (c)

(c)The product decane-1,2-dioic acid is obtained when cyclodecyne undergoes cleavage by KMnO₄ and H₃O⁺. So the hydrocarbon is cyclodecyne. The reaction can be given as:

Hydrocarbon that produces the products in (c)

Step 5: The reactant that gives the products in (d)

(d)The products acetaldehyde, 4-oxopentanoic acid and carbon dioxide are obtained when 5-methylhept-5-en-1-yne undergoes cleavage in the presence of KMnO₄ and H₃O⁺ . So the hydrocarbon is 5-methylhept-5-en-1-yne. The reaction can be given as:

Hydrocarbon that produces the products in (d)

Step 6: The reactant that gives the products in (e)

(e)The hydrocarbon that produces the products 2,7-dioxoheptanoic acid and carbon dioxide is 1-ethynylcyclohex-1-ene. The reaction can be given as:

Hydrocarbon that produces the products in (e)