1. Which of the following compounds is aromatic

according to Huckel's rule?

a) Cyclopropenyl cation

b) Cyclobutadiene

c) Cyclopentadienyl anion

d) Cycloheptatrienyl cation

* e) All of the above

Rationale: Huckel's rule states that a compound is aromatic

if it is cyclic, planar, fully conjugated and has (4n+2) pi

electrons, where n is any integer. All of the options satisfy

these criteria, with n = 0 for a), b) and c), and n = 1 for d)

and e).

2. Which of the following statements is true about antiaromatic compounds?

a) They are more stable than aromatic compounds

b) They are less stable than non-aromatic compounds

* c) They are less stable than both aromatic and nonaromatic compounds

d) They are more stable than non-aromatic compounds

e) They have the same stability as non-aromatic

compounds

Rationale: Anti-aromatic compounds are cyclic, planar,

fully conjugated and have (4n) pi electrons, where n is any

integer. These compounds are highly unstable because they

have an even number of electron pairs in the pi system,

which leads to a high energy state. They are less stable than