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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 thanÂÂ
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