課程名稱︰有機化學三
課程性質︰必修
課程教師︰陸天堯
開課系所︰化學系
考試時間︰Oct.18,2006
是否需發放獎勵金：否
（如未明確表示，則不予發放）
試題 :
1.[10 point]
(a)It is known that cis-decalin is less stable than trans-decalin. Predict the
energy difference between these two stereoisomers based on the number of
the gauche-gauche interaction.
(b)What is the energy difference between cis- and trans-9,10-dimethyldecalins.
Give your reasioning.
R R=H:decalin
╴ ▼ ╴ R=Me:9,10-dimethyldecalin
／ ╲╱ ╲
｜ ｜ ｜
╲╴╱╲╴／
△
R
2.[10 point]
The rate of the reaction of acetone with bromine is first order in acetone
concentration and in hydronium ion concentration but zeroth order in bromine
concentration. Suggest a mechanism that is consistent with such a rate law.
○ ○
∥ + Br2 ──→ ∥ Br + HBr
／＼ ／＼／
3.[10 point]
Use HSAB principle , rationalize the following reaction.
(a) Me3Si-I + MeOPh ──→ MeI + Me3SiOPh
(b)
○ ○ ○
∥ ∥╱ ｜
|\ | ／＼
| \ RCO3H | ╱ ﹨
|／＼ ──→ /| ∕
╱/ \ ＼ ∕/ \ ／
∕/ \ ∕ //___\／
//_____\∕
4.[10 point]
Oxymecuration is a useful electrophilic addition to double bonds. The
mechanism of this reaction is similar to that of bromine addition reactions,
Using frontier molecular orbital theory , rationalize why 4-nitrostyeren
reacts slower than 4-methoxy styrene.
OAC
====== + Hg(OAc)2 ──→ AcOHg╱╲╱
5.[10 point]
In the following reaction,isomer A is formed predominantly.Explain.
／＼
S ｜ ／＼
︳ ｜ ｜ ︱
╴ ╱╲ SH ／﹨ ╱ ＼／ ╱﹨ ／＼S／
／ ╲╱ ╲／╲╱╲╱ ╱∕ ﹨╱ ∕ ／∕ ﹨／ ∕
｜ ｜ ∥ ──→ ∕╲／ ∕ ∕ ∕＼／ ∕ ∕
╲╴╱╲ SH ０ ∕ ∕ ∕ + ∕ ∕ ∕
╲/ ∕／╲ ∕／╲ ∕ ∕╱╲ ∕／＼ ∕
╱ ╲S ╱ ＼S
(A) (B)
ꈠA:B = 98 : 2
6.[10 point]
(a) Compare the most stable conformation of 3,3-dimethylpentane with that of
pentane.
(b) Intramolecular Sn2 reactions of C is slower than that of D. Based on your
conformational analysis of hydrocarbons in (a) , explain the reactivity
difference between C and D.
Cl NaH O
／＼／＼／ ──→ ╱ ╲
HO /\ ﹨ ∕
R R ﹨_∕
/\
R R
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