Download Answer Key for Problem Set 3 1. a) b) c) d) e) f) 2. A 3.

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Answer Key for Problem Set 3
1. a)
OH
b)
OH
c)
OH
HBr (aq)
Br
HCl (aq)
no reaction (needs Lewis Acid)
SOCl2
Cl
N
d)
OH
e)
OH
PBr 3
Br
CH3 SO2Cl
OMs
N
f)
OH
H2SO4
2.
Br
OH
O
PBr 3
Br
Br
A
R- isomer
Br
3.
P
S-isomer
Et
H
H 1. TsCl, pyridine
Et
CN
2. NaCN
OH
3
1
OH
1. TsCl, pyridine
S
2. Na2S
OH
2
4. a)
OH
4
(CF3SO2 )2O
OSO2CF3
THF, H2O
N
b)
NaI
no reaction
acetone
Br H O
2
B
A
OH
c)
NaOH
no reaction
EtOH
OEt
d)
DMF
OMs O
OEt
NaN3
N3
O
E
e)
OTf
+ [(CH 3)2CuCN]Li2
F
f)
HS
OTs
NaH
S
DMF
G
5. a)
SH
H OH
H SPh
Ph3P, DEAD,
THF, 25oC
H
H
1
b)
HN3
O
OH
O
N3
Ph3P, DEAD
2
c)
O
Si
O
Si
PhCOOH
(Bu)4N+F-
Ph3P, DEAD
HO
THF
PChOO
3
OH
PCC,
CH2 Cl2
PChOO
NaOH (aq)
Br
MeOH, THF, H 2O
PChOO
4
6. a)
O
O
HO
6
5
CH3 OH, H2 O
CH3 OH, H2 O
+
+
OCH3
OCH3
(minor)
7
OH
b)
H2SO4
H2O, CH3OH
CH3 OH
OCH3
CH3 OH
OCH3
7.
OH
OH
H2SO4
OH
Ph Ph
O
Ph
Ph
Ph Ph
8.
H3PO4
1. MsCl, Py
OH
2. KOH, EtOH
(E-major)
10
9
9.
HO
H2SO4
O
H
O
OH
11
OH
H2SO4
12
10.
O
C
H
N
protein
O
O
N
H
O
O
+
protein
N
Me
S
HO
O
NH2
NH2
N
OH OH
N
N
S-adenosyl
methionine
O
C
H
N
protein
O
O
N
H
OMe
protein
11.
CH3
H 3C
H 3C
25oC, 5 min
OH
OH
CH3
H 3C
H 3C
CH3
HCl (aq)
H 3C
H 3C
Cl
HCl (aq)
no reaction
H2SO4
OH
Cl- is not a good nucleophile enough to undergo SN2 type substitution reactions
with primary alcohols, but can form an alkyl halide in an SN1 manner after a carbocation
is formed from a tertiary alcohol.
HSO4- is not a good nucleophile, so when tertiary alcohol is heated in H2SO4
solution, only elimination is observed.
12. a)
H2O
-
I
+ OH
I
H2O
+ O
OH
OAc
-
+ I
-
+ I
O
Since OH- is a better nucleophile, first reaction is faster.
b)
(CH 3)3 CBr + H2O
(CH 3)3 COH + HBr
(CH 3)2 CHBr + H2O
(CH 3)2 CHOH + HBr
Since (CH3)3+ is more stable than secondary carbocation, first reaction is faster.
c)
EtOH
I
+ HS
Cl
+ HS
SH + I
EtOH
SH + Cl
Since I- is a better leaving group, first reaction is faster.
d)
+ MsO
+ Cl
Cl
OMs
+ MsO
+ PhSe
SePh
OMs
Since Se is a better nucleophile, second reaction is faster.
e)
Br
EtOH
N3
+ N3
+ Br
(difficult substitution)
EtOH
Br + N 3
N3 + Br
Since second alkyl halide is less hindered, in the SN2 type reaction second one is
faster.
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