Interpretation:
Given that 1-phenyl-2-butene has an ultraviolet absorption at λmax = 208nm (∈ = 8000). On treatment with a small amount of strong acid it isomerizes to give a new compound with λmax = 250nm (∈ = 15,800). A structure for the isomer is to be proposed and a mechanism for its formation has to be suggested.
Concept introduction:
Among two isomers with same molecular formula, the isomer that has extended conjugation will have a higher λmax value than the other.
To propose:
A structure for the isomer which has an ultraviolet absorption at λmax = 250 nm (∈ = 15,800) obtained when 1-phenyl-2-butene with λmax = 208 nm (∈ = 8000) is treated with strong acids. Further to propose a mechanism for its formation.
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