Problems and exercisesUmpolung (polarity inversion)
Exercise 1
Propose a synthesis of 1-phenylpentan-1-one (valerophenone) from benzaldehyde and 1-bromobutane using a dithiane. Compare it with the Friedel–Crafts route.
Exercise 2
Benzoin, PhCH(OH)COPh, is an α-hydroxy ketone. Explain why its disconnection calls for umpolung and how the cyanide ion achieves it in the benzoin condensation.