0930 X1 Pract Ans
14
CH204_F15_X1_Pract_Ans Montgomery College – Takoma Park – Silver Spring Campus Chemical & Biological Sciences Division CHEM204 – Organic Chemistry II Fall 2015 Practice Exam 1 Answers
Transcript of 0930 X1 Pract Ans
CH204_F15_X1_Pract_Ans
Montgomery College – Takoma Park – Silver Spring Campus Chemical & Biological Sciences Division
CHEM204 – Organic Chemistry II
Fall 2015
Practice Exam 1 Answers
CH204_F15_X1_Pract_Ans
Problem 1 1. Treatment of a hydrocarbon A (C9H18) with Br2 in the presence of light forms alkyl
halides B and C, both having formula C9H17Br. Reaction of either B or C with KOC(CH3)3 forms compound D (C9H16) as the major product. Ozonolysis of D forms the fragments shown below. Identify A, B, C, and D.
O O
A B C D
Br
Br
2. Propose a structure for each lettered compound
O
O
EF
E
F
O
O
O 1.LiAlH4
2. H3O+, ∆
G H+
G (major)
H (minor)
CH204_F15_X1_Pract_Ans
Problem 2
Propose a structure for the lettered compounds.
NBSI J
KOC(CH3)3
K
NBS
hν
NaOH PCCM (C6H10) N O + Q PQ
P
O
K
I
J
Br
K
M
N
Br
O
Q
OH
P
O
CH204_F15_X1_Pract_Ans
Problem 3
Complete the following reactions by giving the major organic product(s). Write NR if no reaction occurs.
1 O
OH
PCC
CH2Cl2
O
O
2
CHO
O
OH
KMnO4
H3O+
O
OOH
O
3
Br
Na2Cr2O7
H3O+
No Reaction
4
O
O
OH
Na2Cr2O7
H2SO4 (aq)
O
O
O
5
1. mCPBA2. LiAlH4
3. CH3Cl
O
6
O
OH
1. NaH
2. CH3Br
O
O
CH204_F15_X1_Pract_Ans
7
OCl
1. LiAlH4
2. H2O
H OH
8
O
O
OOHCl
OO
9
DBr
DBr
D
Br
10
OO
O
O
O
O
O
O
11
O
O OO
No Reaction
12
O
O
O O
CH204_F15_X1_Pract_Ans
Problem 4
A symmetrical cyclic compound, Q (C5H10O2) reacts rapidly with KMnO4 under acidic conditions to give compound R(C5H6O2) as the sole product. Compound Q does not react with H2 over a platinum catalyst. When Q is dehydrated, it yields compound S (C5H6). When S is reacted to one equivalent molar of DBr, two isomeric products were isolated, T and U. T is the 1,2-product. Proton NMR of R shows two singlets with a 2 to 1 relative area. Deduce the structures of Q, R, S, T and U. Q R S T U
OHOH
OO
Br
D
DBr
Problem 5 Circle the aromatic compounds
OO
O
S
NH
O
B
O
N
N O
CH204_F15_X1_Pract_Ans
Problem 6 Draw a stepwise mechanism for each of the following reactions: (a) 2,3-Epoxy-2-methylbutane is reacted with LiAlH4/H2O followed by treatment with acid and heat.
OH Al
-H
H
H
O-
H
H OHO
H
H
O
H
HH
O+
H
H
H
O+
H H
HH
H OH
(b) 1,3-cyclohexadiene is reacted with 1 eq. DBr.
D Br
+
+
(1) (2)
(1)-Br
(2)
D
D
DBr
+ D
+
D-Br
D
Br
CH204_F15_X1_Pract_Ans
(c) 1-methyl-1,3-cyclopentadiene is reacted with NBS and light.
NBS
hνN
O
O
BrNBS =hν ..N
O
O
Br
H.Br
H
H.Br
.
.
. .
.
. .Br.
Br BrBr Or Br
(1) (2) (3)
(4) (5)
Ha
Hb
Attacking Ha
Attacking Hb
Last Step (two possible paths) for Intermediate (1)
(1)
The other products are obtained by the same mechanism for the other intermediates
Br Br
Br
Br
(2) (4) (5)(3)
.(6)
Br
(6)
.
(7)
(7)
CH204_F15_X1_Pract_Ans
Problem 7
Label each compound as aromatic or not. Assume all completely conjugated rings are planar. The lone pairs are not shown.
(a)
O
N
Aromatic
(b)
O
(c)
S
Aromatic
(d)
S
(e)
+
Aromatic
(f)
Aromatic
(g)
O
B
Aromatic
(h)
O
(i)
(j)
(k)
(l)
O
CH204_F15_X1_Pract_Ans
Problem 8
Propose a structure for each lettered compound. 1.
1. LiAlH4
2. H3O+
O
OH
F(C6H10O)G(C7H12O)
H(C13H22O2)
F G H
O
O
O
O
2.
I (C6H10)J(C6H8O2)
K(C12H18O2)H2
Pt
OH
OH
I J K
O
O O
O
CH204_F15_X1_Pract_Ans
Problem 9
Complete the following reactions by giving the major organic product(s). Write NR if no reaction occurs.
1
OH NO2
HNO3
H2SO4
OH NO2
NO2
+OH NO2
O2N
2 OH
SO3
H2SO4
OH
SO3H
3
O
Br2
FeBr3
OBr
4
AlCl3
Cl
5
KMnO4
H3O+
O
OH
O
OH
6
Cl
Br2
hν
Cl
Br
CH204_F15_X1_Pract_Ans
7
O
Cl
1. Zn(Hg), HCl
2. Cl2/FeCl3
Cl Cl
8
NO2
1. CH3Cl / AlCl3
2. Fe, HCl
NH2
9
O
Br
1. Cl2 / AlCl3
2. LiAlH4 3. H3O+, ∆
Br
Cl
10
O
Cl
HNO3
H2SO4
O
Cl
NO2
11
O
O
CH3COCl
AlCl3
O
OO
+ O
O
O
12
OO
O
1. N2H4, OH-
2. KMnO4, H3O+
OO
OHO O
OH
CH204_F15_X1_Pract_Ans
Problem 10 Draw a stepwise mechanism for each of the following reactions and draw the structure of the major product(s).
1.
O
HNO3
H2SO4
Show all resonance forms Electrophile formation (1 points)
HNO3 + SO
OOHOH H2NO3
+HSO4
- + NO2+ + H2O
Ortho Attack (2 points)
NO2
H
O
HNO2
O
H
NO2
O
HNO2
O
++ +
NO2+ H
NO2
O
+H2O
Meta Attack (2 points)
H
NO2
O
H
NO2
O
H
NO2
O
+
+ +H
O
NO2+ H
NO2
O
+ H2O
Para Attack (2 points)
H NO2
O
H NO2
O
H NO2
O
++
+
H
O
NO2+
HO2N
O
+H2O
Explain why the meta product is the major product (2 points.) The ortho/para attacks leads to very unstable intermediates (circled in red) favoring thus the meta attack.
CH204_F15_X1_Pract_Ans
2.
OH+ Cl
AlCl3
Show all resonance forms Electrophile formation (1 points)
Cl
AlCl3
Cl+
Al-
Cl
Cl Cl
+ + Ortho Attack (2 points)
HOH
H
OH
H
OH
H
OH
++ +
HOH
+H2O+ H
O+
Meta Attack (2 points)
H
OH
H
OH
H
OH
+
+ +HOH
H
OH+ H2O
+
Para Attack (2 points)
H
OH
H
OH
H
OH
++
+
HOH
H
OH
+H2O
OH
+ H
O+H
Explain why the ortho/para product is the major product (2 points.) The ortho/para attacks lead to 4 resonance forms where one respects the octet rule while the meta attack leads to only 3 forms none of which respects the octet rule.
