Q5(c). 290 nm or 450 nm for a reaction through T₁?
A photochemical reaction takes place through the T₁ state. S₀–S₁ and S₀–T₁ energy gaps correspond to 290 nm and 450 nm, respectively. To get an efficient photochemical reaction should we use light of 290 nm or 450 nm? Give your answer presenting the relevant Jablonski diagram.
Answer in brief
Use 290 nm light: S₀ → S₁ is spin-allowed and is followed by fast intersystem crossing to T₁.
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CoversJablonski diagramintersystem crossingtriplet statespin-forbidden transitiontriplet sensitiser
All parts of Question 5
- 5(a) Dichloroacetyl chloride with Et₃N, then cyclopentadiene10 marks
- 5(b) Starting material A and the intermediates10 marks
- 5(c) 290 nm or 450 nm for a reaction through T₁?10 marks
- 5(d) Rotational spectroscopy10 marks
- 5(e) NMR at two field strengths; mass spectrum of a ketone10 marks