When pseudoionone is treated with BF3 in acetic acid, ring closure takes place and α-and β-ionone are produced. This is the next step in the vitamin A synthesis.

(a) Write mechanisms that explain the formation of α-and β-ionone.
(b) β-Ionone is the major product. How can you explain this?
(c) Which ionone would you expect to absorb at longer wavelengths in the UV-visible region? Why?

Transcribed Image Text:

BF HOAC a-lonone β-Ionone Pseudoionone