Question

The number of optically active products obtained from the complete ozonolysis of the given compound is :

• A. 0
• B. 2
• C. 4
• D. 4

Hint:

When analyzing ozonolysis of chiral compounds, carefully consider the stereochemistry at the chiral centers and how they are retained (or lost) in the products. If the ozonolysis generates chiral products, remember that each chiral compound contributes one optically active product (and its enantiomer is another optically active product).

Answer 1

The Correct Option is B

To determine the number of optically active products obtained from the complete ozonolysis of the given compound, we must follow these steps: 

1. Understand the structure of the given compound. The compound is a diene with chirality centers, as shown in the image below:
2. Ozonolysis Reaction: Ozonolysis of alkenes cleaves the double bonds, forming carbonyl compounds. In this reaction, each double bond will break to form carbonyl groups (aldehydes or ketones).
3. Analyze the reaction products:
   • The given compound has two double bonds, which means it will produce two pairs of carbonyl compounds after ozonolysis.
   • The cleavages occur at the double bonds present in the molecule, breaking it down into simpler products.
4. Chirality Consideration: After ozonolysis, the chirality centers (if present) must be analyzed to determine optical activity.
   • Formation of chiral centers can lead to optically active (enantiomeric) products.
   • In this compound, ozonolysis results in the formation of ketones or aldehydes, some of which have asymmetric carbon centers.
5. Counting Optically Active Products:
   • Examine each product for chirality, considering symmetry and asymmetry around carbon centers.
   • In this case, ozonolysis leads to two optically active products because there are two products with asymmetric carbon centers that exhibit chirality.

Conclusion: The correct answer is \(2\), as the complete ozonolysis of the given compound results in two optically active products.

Answer 2

Step 1: Understand ozonolysis of alkenes.
Ozonolysis of alkenes followed by reductive workup yields carbonyl compounds. The carbon-carbon double bonds are cleaved, and oxygen atoms are attached to the carbon atoms of the double bond, forming aldehydes or ketones.
Step 2: Identify the chiral centers and the products of ozonolysis.
The given compound has two chiral centers with opposite configurations. Ozonolysis will cleave the three double bonds, resulting in the following organic products:
1. \( CH_3CHO \) (ethanal - achiral) 2. \( H-\overset{CH_3}{\underset{H}{\mathrm{C}^}}-CHO \) (2-methylpropanal - chiral) 3. \( OHC-CHO \) (glyoxal - achiral) 4. \( OHC-\overset{H}{\underset{CH_3}{\mathrm{C}^}}-CHO \) (2-methylmalondialdehyde - chiral) 5. \( OHC-CHO \) (glyoxal - achiral)
Step 3: Determine the number of optically active products.
The chiral products formed are 2-methylpropanal and 2-methylmalondialdehyde. Due to the opposite configurations at the chiral centers in the starting material, the resulting chiral aldehydes will be enantiomers of each other. The first chiral center yields one enantiomer of 2-methylpropanal.
The second chiral center yields the other enantiomer of 2-methylpropanal.
These two enantiomers are the optically active products. Glyoxal and ethanal are achiral. Therefore, the number of optically active products is 2.