Question

An organic compound (X) on reductive ozonolysis gave 1 mole of propanal-pent-3-one. Name the organic compound X.

Hint:

For reverse ozonolysis problems, simply erase the ‘=O‘ from the products and connect the bare carbons with a double bond to find the reactant alkene.

Answer 1

Step 1: Understanding the Concept:
Reductive ozonolysis cleaves carbon-carbon double bonds ($C=C$) to form carbonyl compounds (aldehydes and ketones). To determine the structure of the original alkene (X), we work backward: place the carbonyl oxygen atoms of the products facing each other, remove them, and connect the corresponding carbon atoms with a double bond.

Step 2: Key Formula or Approach:
The problem text "propanal-pent-3-one" contains a typographical error and should be interpreted as yielding a mixture of "propanal and pentan-3-one".
Draw the structures of the products, align their carbonyl groups, and reconstruct the alkene.

Step 3: Detailed Explanation:
Assuming the products are 1 mole of propanal and 1 mole of pentan-3-one.
Structure of Propanal: $\text{CH}_3-\text{CH}_2-\text{CH}=\text{O}$
Structure of Pentan-3-one: $\text{O}=\text{C}(\text{CH}_2\text{CH}_3)_2$
To find compound X, align the molecules so the carbonyl oxygens face each other:
$\text{CH}_3-\text{CH}_2-\text{CH}=\text{O} \quad + \quad \text{O}=\text{C}(\text{CH}_2\text{CH}_3)_2$
Remove the oxygen atoms and join the carbonyl carbons with a double bond:
$\text{CH}_3-\text{CH}_2-\text{CH}=\text{C}(\text{CH}_2\text{CH}_3)_2$
Let's find the IUPAC name for this reconstructed alkene.
1. Identify the longest carbon chain containing the double bond. The longest chain spans 6 carbons.
$\text{C}_1\text{H}_3-\text{C}_2\text{H}_2-\text{C}_3\text{H}=\text{C}_4(\text{CH}_2\text{CH}_3)-\text{C}_5\text{H}_2-\text{C}_6\text{H}_3$
2. Number the chain to give the double bond the lowest possible number. Numbering from left to right gives the double bond at position 3. Numbering right to left also gives position 3.
3. Apply the substituent rule. Numbering left to right gives the ethyl group position 4. Numbering right to left gives the ethyl group position 3. Lower locant rule dictates right-to-left numbering.
Let's re-number correctly right to left:
$\text{C}_6\text{H}_3-\text{C}_5\text{H}_2-\text{C}_4\text{H}=\text{C}_3(\text{CH}_2\text{CH}_3)-\text{C}_2\text{H}_2-\text{C}_1\text{H}_3$
The substituent is an ethyl group at carbon 3.
The name is 3-ethylhex-3-ene.

Step 4: Final Answer:
The organic compound X is 3-ethylhex-3-ene.