Question

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

Butanedial

Short answer

Answer

Structure of parent hydrocarbon

Step-by-step solution

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.

O3 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