Question

3. (7 points total) Hydrocarbon A, C10H14, has a UV absorption at Amax = 236 nm. Upon catalytic hydrogenation (H2, Pd/C), Hydrocarbon B, C10H18, is formed. Ozonolysis of A, followed by zinc/acetic acid treatment, yields the following diketo dialdehyde: a. (4 points) Propose two possible structures for hydrocarbon A: b. (3 points) Based on the UV data, which proposed structure for A is correct? Why? Justify your answer with Woodward-Fieser calculations.

Answer 1

b)From woodward fieser calculation , structure (i) have lambdamax =234

lambdamax for (i) = 214(base) + 15 (3 ring residue) + 5 (exocyclic C=C ) = 234 nm.

for (ii) = 214(base) + 20(4ring residue) = 234nm but the observed value here is 236 nm.

Therefore, structure (ii) is the correct structure.