Q10(b). Electronic transitions of acrylaldehyde; hexane to ethanol
Describe the electronic transitions in acrylaldehyde. Comment if these are allowed or forbidden and the changes observed in UV spectrum when the solvent is changed from hexane to ethanol.
Answer in brief
π → π* (near 210 nm) is allowed and intense; n → π* (near 315 nm) is forbidden and weak; in ethanol π → π* shifts to longer and n → π* to shorter wavelength.
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Coversacroleinπ→π* transitionn→π* transitionsolvent effectbathochromic shifthypsochromic shift
All parts of Question 10
- 10(a) Reformatsky reaction and dehydration; Doebner synthesis10 marks
- 10(b) Electronic transitions of acrylaldehyde; hexane to ethanol5 marks
- 10(c) Thermal [1,3] shift: hydrogen cannot migrate, carbon can5 marks
- 10(d) Spectral structure problem: the liquid from acetone and base10 marks