Q8-62 E - Organic Chemistry (Mcmurry)

Question

Draw the structure of a hydrocarbon that absorbs 2 molar equivalents of H2 on catalytic hydrogenation and gives only butanedial on ozonolysis.

Butanedial

Step-by-Step Solution

Answer

Answer

Structure of parent hydrocarbon

Step 1: Catalytic hydrogenation

Catalytic hydrogenation is a reaction of alkene or alkyne with hydrogen in the presence of a metal catalyst like nickel, palladium, or platinum. Hydrogenation reduces double and triple bonds in hydrocarbons and adds hydrogen.

Step 2: O 3 and Zn reactions

When an alkene is treated with ozone and subjected to reductive workup with zinc, the carbon-carbon double bond is cleaved to give ketones or aldehydes, which depend on the alkene structure.

Step 3: Reaction interpretation

• In the reaction, as only 1 mole of dihydrogen is used, it indicates only one bond is broken, and only two hydrogens are attached to 1 mole of C₁₀H₁₆. 
• As here reaction with O₃  and Zn is giving a single product, the molecule must be symmetrical on both sides of the double bond. 
• As one product is of four carbon, the parent hydrocarbon will be of eight carbon.

Step 4: Structure interpretation

According to the steps mentioned above earlier, the possible structure of the parent, hydrocarbon, is given as

Structure of parent hydrocarbon