91Ó°ÊÓ

Question: Devise a stepwise mechanism for the conversion of M to N. N has been converted in several steps to lysergic acid, a naturally occurring precursor of the hallucinogen LSD (Figure 18.4).

Question. Draw all possible resonance structures for the following cation and indicate which structure makes the largest contribution to the resonance hybrid.

Question. Determine the hybridization of the labelled atom in each species.

a.

b.

c.

Question: Which diene in each pair has the larger heat of hydrogenation?

a.

or

b.

or

Question: Draw additional resonance structures for each ion.

a.

b.

c.

d.