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11.
Predict which of the following carbocations has the highest energy:
Higher energy means less stable. Stability is related to how much the charge can be spread out,
which is, in this case, related to whether alkyl groups (substitution pattern) behave as electron
withdrawing or donating groups. The answer is (A)
12.
Bromination of alkanes is a much slower reaction than chlorination. Which of the following is
expected to be the major organic product when 2-methylbutane is allowed to react with Br
2
in the
presence of light or heat?
The answer here is (B). How is rate of a reaction related to selectivity? Which hydrogen in the
reactant is the most reactive towards radical abstraction?
13.
Which of the following free radical is the most stable ?
CH
2
CH
3
CH
3
CH
3
CH
3
(a)
(b)
(c)
(d)
(e)
How is radical stability affected by substitution pattern? (answer is (B))
14.
Which of the above drawing is the most stable if the radical carbon is changed to a carbocation?
(answer is B)
CH
3
CH
2
CHCH
3
CH
3
+ Br
2
light
CH
3
CH
2
CHCH
2
Br
CH
3
CH
3
CH
2
CCH
3
CH
3
Br
CH
3
CHCHCH
3
CH
3
Br
BrCH
2
CH
2
CHCH
3
CH
3
(A)
(B)
(C)
(D)
CH
3
CH
3
CH
2
(E) All are equally stable
(C)
(B)
(A)
CH
3
(D)