Question

Choose the correct statement(s) with regard to the terpenes given below.

• A. Upon ozonolysis, all the terpenes would produce at least one identical carbonyl compound
• B. Terpenes N and O are geometrical isomers
• C. Terpene O cannot undergo Diels-Alder reaction with maleic anhydride
• D. Amongst all, $\lambda_{\max}$ for $\pi-\pi^*$ absorption is the lowest for terpene P

Hint:

Greater conjugation increases $\lambda_{\max}$For Diels-Alder reaction, look for a conjugated diene capable of adopting s-cis conformation

Answer 1

The Correct Option is A, B, D

Step 1: Observe the common terpene framework.
All the given structures are acyclic monoterpene-type moleculesThey contain two isoprene units and have carbon-carbon double bonds at different relative positions

Step 2: Analyze ozonolysis products.
Ozonolysis cleaves carbon-carbon double bonds and converts the alkene carbons into carbonyl compoundsSince all the given terpenes contain a common substituted alkene fragment, cleavage of that part gives at least one identical carbonyl compound

Step 3: Check statement (A).
Because all four terpenes have a common alkene portion, their ozonolysis gives at least one common carbonyl productTherefore, statement (A) is correct

Step 4: Compare terpenes N and O.
Terpenes N and O have the same molecular formula and same connectivityThey differ only in the spatial arrangement around a carbon-carbon double bondThus, they are geometrical isomers

Step 5: Check statement (B).
Since N and O differ only as E/Z forms around the double bond, statement (B) is correct

Step 6: Analyze Diels-Alder possibility for terpene O.
Terpene O contains a conjugated diene systemA conjugated diene can undergo Diels-Alder reaction with an electron-poor dienophile such as maleic anhydrideTherefore, statement (C), which says that O cannot undergo Diels-Alder reaction, is incorrect

Step 7: Compare $\lambda_{\max}$ values.
$\lambda_{\max}$ for $\pi-\pi^*$ absorption increases with conjugationTerpene P has the least effective conjugation among the given structures, so it absorbs at the lowest wavelengthHence, statement (D) is correct
\[ \boxed{\text{(A), (B) and (D)}} \]