Q8-58 E-c - Organic Chemistry (Mcmurry)

Question

Compound A has the formula ${\mathbf{C}}_{\mathbf{10}}{\mathbf{H}}_{\mathbf{16}}$. On catalytic hydrogenation over palladium, it reacts with only 1 molar equivalent of ${\mathbf{H}}_{\mathbf{2}}$. Compound A also reacts with ozone, followed by zinc treatment, to yield a symmetrical diketone, B$\left(C_{10}{H}_{16}{O}_2\right)$.

Write the reactions.

Step-by-Step Solution

Answer

Answer

The reaction of compound A with dihydrogen and palladium

The reaction of compound A to form compound B

Step 1: Catalytic hydrogenation

Catalytic hydrogenation is the 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, depending 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 ${\mathrm{C}}_{10}{\mathrm{H}}_{16}$. 
• As here, O₃ and Zn are used in the second step, which results in symmetrical diketone formation. This indicates the presence of one ene group
• Symmetrical diketone presence indicates that carbons having double bonds have no hydrogen; otherwise, aldehyde will form.
• So, there must be two rings in compound A having a double bond between them.

Step 4: Structure interpretation

The compounds can be identified by utilizing the steps outlined above. Based on the given information, here is a list of probable compounds:

Structure of compound A

Structure of compound B

Step 5: Catalytic hydrogenation reaction

The hydrogenation of the double bond present in the compound gets reduced and results in a formation of a bicyclic compound.

The reaction can be shown as:

Catalytic hydrogenation

Step 6: O 3 and Zn reaction

The double bond present in the compound gets cleaved and get converted into a symmetrical diketone compound.

The reaction can be shown as:

O₃ and Zn reaction