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OCH701S - ORGANIC CHEMISTRY 2 - 2ND OPP - JULY 2023 |
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1.1 Page 1 |
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n Am I BI A u n IVE Rs ITY
OF SCIEnCE
TECHnOLOGY
FACULTYOF HEALTH,NATURALRESOURCESAND APPLIEDSCIENCES
SCHOOLOF NATURALAND APPLIEDSCIENCES
DEPARTMENTOF BIOLOGY,CHEMISTRYAND PHYSICS
QUALIFICATION:BACHELOROF SCIENCE
QUALIFICATIONCODE: 07BOSC
LEVEL: 7
COURSECODE: OCH701S
COURSENAME: ORGANIC CHEMISTRY 2
SESSION:JULY 2023
PAPER:THEORY
DURATION: 3 HOURS
MARKS: 100
SUPPLEMENTARY/ SECONDOPPORTUNITYEXAMINATION QUESTION PAPER
EXAMINER(S} DR. MARIUS MUTORWA
MODERATOR: DR. RENATE HANS
INSTRUCTIONS
1. Answer ALL the questions.
2. Write clearly and neatly.
3. Number the answers clearly
4. All written work must be done in blue or black in and sketches
must be done in pencil
5. No book, notes and other additional aids are allowed
A.
B. PERMISSIBLEMATERIALS
Non-programmable Calculators
C. ATTACHMENTS
NMR and IR Spectral Data, pKa Chart and Periodic Table
THIS QUESTION PAPERCONSISTSOF 13 PAGES{Including this front page)
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SECTIONA
[SO)
QUESTION 1: Multiple Choice Questions
• There are 25 multiple choice questions and each question carries 2 marks.
• Answer ALL questions by selecting the letter of the correct answer.
[SO]
1.1 Which of the following compounds will show a broad absorption around 3300 cm-1 and at 1650
cm-1?
'o OH
00
0
OH
0
0
OH
Il
m
ff
\\"
A.
B. II
C. Ill
D. IV
E. V
1.2 Which of the following compounds will have odd m/z value for the molecular ion?
0
H~N/
II
I
.,,,,N_ _/'"--.-.._ /
.,,r ......__,,,,,, '"N
I
I III
A. I
B. II
C. Ill
D. IV
E. None of the above
1.3 Identify the structure for a compound that is consistent with the following data.
a. The molecular ion peak has m/z = 116
b. The base peak is at m/z = 59.
c. The compound is composed of C, Hand O atoms.
d. The JRspectrum shows a strong absorbance at 3257 cm-1•
~OH
OH
A
B
C
o·
E.
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A.A
B.B
c.c
D.D
E. E
1.4 For the following reaction sequence (it is not necessary to understand the chemistry) what
significant change(s) would be expected by IR (ignoring C-H absorptions)?
.. a. CH3MgBr
A. A peak around 1710 cm-1 would disappear and a new peak around 3300-3500 cm-1 would
appear.
B. A peak around 1710 cm-1 would appear and a new peak around 1650 cm-1 would disappear.
C. A peak around 2150 cm-1 would disappear and a new peak around 3300-3500 cm-1 would
appear.
D. No change would be observed.
1.5 A compound has two signals in the 13C NMRspectrum and a single signal in the 1H NMR
spectrum. Which is the most likely compound?
A. dimethyl ether
B. diethyl ether
C. 2,2-dimethylpropane
D. methyl ethanoate
1.6 How many proton NMR singlets will 2-bromo-3-methyl-2-butene exhibit?
A.1
B.2
C. 3
D.4
E. 5
1.7 Which of the indicated protons in the following compound would appear most upfield in the 1H
NMR spectrum?
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1.4 Page 4 |
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A. I
B. II
C. Ill
D. IV
E. I & IV
1.8 What is the product of the following reaction?
0
?
A.
B.
C.
A.A
B.B
c.c
D. None of the above
1.9 Treatment of the diene below gives a mixture of products. Predict the major product under the
given conditions.
c5 H-Br
?
150°C
A. A
B. B
C. C
D. D
A
8
C
D
1.10 Which of the following compound (s) show conjugation?
-0
•
A.
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A.A
B.B
c.c
D. B & C
E. All of the above
1.11 Why is the following compound not aromatic?
A. It has 4n electrons
B. It isn't planar
C. It has 4n+2 electrons and then: electron system in continuous
D. It isn't planar and then: electron system is not continuous
1.12 Name the following compound.
A. 2,3-dibromoaniline
B. 2-bromo-5-aminobromobenzene
C. 2-bromo-3-aminobromobenzene
D. ortho-dibromonitrobenzene
1.13 Which one of the following compound is aromatic?
A. I
B.11
C. Ill
D. IV
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1.14 How many rr-orbital electrons are in the following molecule?
N• .
f.J
N
I
H
A.4
B.6
C. 8
D.10
1.15 Which is the best reaction sequence for preparing the following compound from benzene?
ONO, 0
II
COH
-
AlCI_,
CH3Ct
I :::,.__
-A--lC-I._,
X
H3CCI
II
0
K,CnO~
H2S04
A
HN03.
H2S04
C
HN03
H2so:
A.A
B.B
c.c
D.D
HN03
H2S04
AlCl3
CH3Cl
B
AlCl3
CH3Cr
HN03
H2S04
D
K2Cr207
H2S04
,. K2Cr201
H2S04
1.16 Both LiAIH4and NaBH4are reducing agents. Which statement about these reagents is true?
A. Both reagents contain polar metal-hydrogen bonds. The polarity of the B-H bond is greater
than the polarity of the AI-H bond, so LiAIH4is the stronger reducing agent.
B. Both reagents contain polar metal-hydrogen bonds. The polarity of the B-H bond is greater
than the polarity of the AI-H bond, so LiAIH4is the weaker reducing agent.
C. Both reagents contain polar metal-hydrogen bonds. The polarity of the B-H bond is less than
the polarity of the AI-H bond, so LiAIH4is the stronger reducing agent.
D. Both reagents contain polar metal-hydrogen bonds. The polarity of the B-H bond is less than
the polarity of the AI-H bond, so LiAIH4is the weaker reducing agent.
1.17 At which site on the following substrate will electrophilic substitution be most likely to occur,
in the formation of a tri-substituted product?
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A.A
B.B
c.c
D.D
1.18 Which reaction can accomplish the following transformation in good yield:
?
A. w I H2O
B. oxymercuration /oxidation
C. hydroboration/oxidation
D. reaction with NaOH
1.19 The reaction between 4-methyl-1-pentanol and HBr to yield 4-methyl-1-pentene is probably:
A. an SNl reaction involving protonated alcohol as a substrate
B. an SN2 reaction involving protonated alcohol as a substrate
C. an El reaction involving protonated alcohol as a substrate
D. an E2 reaction involving protonated alcohol as a substrate
1.20 The final product D, in the following reaction sequence would be?
)--OHPBr3
Mg
A
B
H30-
C
D
ether
0
---;P
A. A';(H
B. ~,.
C. ~OH
D.
OH
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1.21 Rankthe following acids in decreasing (strongest to weakest) order of acidity.
0
0
II
II
COH
COH
~)¢
0
0
II
II
COH
COH
¢
OCHi
N02
CH3
Cl
I
II
III
IV
A. I > 11>1 IV > II
B. II > IV> Ill > I
C. II > Ill > I > IV
D. I> IV> II> Ill
E. 11> IV > I > 111
1.22 What is the first step in nucleophilic addition to a carbonyl compound under acidic conditions?
A. protonation of the nucleophile
B. addition of the nucleophile
C. protonation of the carbonyl carbon
D. protonation of the carbonyl oxygen
1.23 What is the correct IUPACname for the following compound?
H
A. 2,6,6-trimethylbenzaldehyde
B. 1,1,3-trimethylbenzaldehyde
C. 2,6,6-trimethyl-1,3-cyclohexadienecarbaldehyde
D. 1,1,3-trimethyl-2,4-cyclohexadienecarbaldehyde
1.24 Predict the product for the following reaction.
0
/"-.._
r~OH
l.UAIH4
2.H20
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A. 3-methyl-2-pentanone
B. 3-methyl -1-propanol
C. 2-methyl-1-butanol
D. 3-methyl-2-pentanol
1.25 Which of the following will allow the reaction below to proceed as written?
A. Addition of heat
B. Addition of an acid catalyst
C. Addition of a base catalyst
D. Addition of heat and an acid catalyst
END OF SECTIONA
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SECTIONB
QUESTION 2
Identify the lettered intermediates (A-H) in the following reaction sequence.
Note: 2 marks for each intermediate
NaCN
A
H3Q+
[1] UAIH4
1[2] H2O
C
[50]
[16]
QUESTION 3
[16]
Draw a full detailed mechanism for the reaction below. In order to receive full marks, show all
intermediates and flow of electrons using the appropriate arrows.
Note: 1 mark for each appropriate arrow
0
~OCH
3
OCH 3
5,5-dimethoxy-2-pentanone
y
QUESTION 4
[18]
Use the 1H NMR spectrum provided below to identify the structure of compound Y with Molecular
Formula C1H14OC. ompound Y shows a strong absorption in its IR spectrum at 1713 cm-1.
1H NMR of Y
8
7
6
6H
2H
2H
3H
1H
1
------ _J!k_ -----\\--..
5
4
3
2
1
0
ppm
THE END
GOODLUCK
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2 Pages 11-20 |
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1H NMR SPECTRALDATA
Characteristic Chemical Shifts of Common Types of Protons
Type of proton
Chemical shift (ppm)
Type of proton
Chemical shift (ppm)
• RCH 3
• R2CH 2
• R3CH
z,, I
;C-C-IH
Z=C, 0, N
0.9--2
-0.9
-1.3
-1.7
1.5-2.5
\\
/H
I
C=C
l'
\\
sp2
0-H
4.5--6
6.5---8
9--10
0
II
-2.5
R...C- 'OH
10-12
-6-H sp 3/I Z
2.5-4
Z= N, 0, X
RO-H or R-N-H
1-5
I
Bond type
Important IR Absorptions
Approximatev (cm-1)
0-H
N-H
3600--3200
3500--3200
C-H
• Cs,,,2-H
• Cs,o2-H
• Cs,o-H
C=C
-3000
3000-2850
3150-3000
3300
2250
C=N
2250
C=O
1800--1650 (often - 1700)
C=C
1650
0
1600, 1500
Intensity
strong, broad
medium
strong
medium
medium
medium
medium
strong
medium
medium
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conjugate acid
sulfuric acid
H2S0 4
hydroiodic acid
HI
hyclrobromic acid HBr
hydrochloric acid
.•
HC..I:
H
/'J carboca tions
+
protonated
alcohol
/'---· OI•.+.,Hl
H
hydronium ion H,...0...I'+H
H
nitric acid
HN0 3
hydrofluoric acid HF
:o:
carboxylic acids ~ 0•• ,..H,.
conjugate base
... Hso;
,-
-
.. B.r.-
:c.1.:
...
.. /'---o..,H
H...•0.•.·.'.H
N03
...
-
F
.. :o:
~a:..
pKa Chart
conjugate acid
conjugate base
-10
hydrogen cyanide H-C=N:
... :c=N:
9.1
-9
phenols
cr?_H er~=- ..
(cyanide)
10
-8
-7
water
. .•O.
H,.... 'H
- :o..-..H
15.7
-3
.. primaiy alcohols /'--- .o...,H
(hydroxide)
/'---.a. : 16
(alkoxides)
-2.4
alkynes
c=c-H
c=c:
26
(acetylide anions)
-1.7
hydrogen
H-H
H
I
-1.3
lllllnonia/ amines
R,..N.•.·0' H
3.2
alkanes
4.8
H
:H (hydride) 35
·N ~
R,...."·'H
36
(amide bases)
. ..........-......
~60
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hydrogen
1
H
1.0079
llhlum
3
Li
3.£41
sodium
11
Na
22.990
pdaislum
19
K
S9.098
rLbidium
37
Rb
85.468
caesium
55
Cs
13,.9'
87
Fr
12231
ber}lliLm
4
Be
9.0122
magnesium
12
Mg
24.305
colclum
20
Ca
40.079
s:ronlium
38
Sr
87.62
Jarium
56
Ba
13,.33
·adium
88
57-70
*
89-102
** Ra
12261
scrndiun
21
tlt~nlJrr
22
vanajlum
23
Sc Ti V
41-.956
yllrium
39
y
47.e67
zirconium
40
Zr
E0.942
nobiun
41
Nb
88.906
lutetium
71
Lu
91.224
hafnium
72
Hf
92.906
tantalum
73
Ta
174.97 178.49 180.95
l,wranclu11 rutherfordlJrn dubnlum
103 104 105
Lr Rf Db
12621
12611
12621
chromium manganes" lror
24
25
26
Cr Mn Fe
5U96
54 938
molybdenum le:hnelum
42
43
55.B45
rulreniun
44
Mo Tc Ru
95.94
lun,sten
w74
1981
rhenium
75
Re
101.07
0s11lum
76
Os
183.84
,eaborgum
106
183.21
bohrlum
107
180.23
hasslum
108
Sg Bh Hs
12661
1~·
1269]
boron
5
carb:>n
6
nl:ro;ien
7
BCN
1C.B11
aumin um
13
Al
12.011
sllcon
14
Si
14.007
fhosphorus
15
p
27
Co
SB.933
rh:xforr
45
Rh
nictel
28
coi:per
29
Ni Cu
58.692
paltadiu11
46
63.346
silver
47
Pd Ag
znc
30
Zn
GE.39
cadmium
48
Cd
2E.982
gallum
31
28.036 3).974
germaniu11 arsenic
32
33
Ga Ge As
6s.723
indiu11
72.61
tin
74.922
anlirrony
49
50
51
In Sn Sb
102.91
irdium
77
Ir
106.4,
platinum
78
Pt
'07.8 7
gold
79
Au
112.41
mercury
80
Hg
114.82
lhalllLm
81
Tl
118.71
laa,j
82
Pb
121 76
blsrruth
83
Bi
192.22
195.0E
'9f.9 7
200.53 2C4.38
mellnerium ununnillLm unJnuniJm ununbium
109 110 111 112
Mt UunUuuUub
2072
23898
urunquadium
114
Uuq
1268]
·2111
12721
12771
[289]
cxygen
8
0
15.999
sulfur
16
s
:i2.065
selenlu11
34
Se
7B.96
lellu·ium
52
Te
127.60
polonlun
84
Po
12091
lluorine
9
F
1B.99a
chlorlre
17
Cl
35.453
bromine
35
Br
79.904
iocine
53
I
126.90
astatlre
85
At
12101
helium
2
He
4.00,6
neon
10
Ne
201EO
argo1
18
Ar
39.948
krwton
36
Kr
83.80
xenon
54
Xe
13U9
rado1
86
Rn
1,221
*Lanthanide series
**Actinide series
IJnllrn1um
57
La
138J1
acllnlum
89
Ac
[22?)
oorium
58
Ce
14012
lrorurr
90
Th
23204
p-as,odymiuI neJdymlurn prJmethlum sgmariun
59
60
61
62
Pr Nd Pm Sm
14(.9·
pro:adinum
91
Pa
144.24
uranium
92
u
114!:l
n,pb.mum
93
Np
150.36
pluloniun
94
Pu
231.04 238.03
1,371
124'-)
eu·o,ium Jadolnium
63
64
Eu Gd
151.96 157.25
arnerlclu11 cururr
95
96
Am Cm
1243)
12,n
lartlum
65
Tb
158.93
berkelium
97
Bk
[2471
d\\spnslum 1olmlum
66
67
Dy Ho
162.50 164.9,
californum elns:einlum
98
99
Cf Es
1251'
125,1
erbium
68
lhullum
69
Er Tm
167.26 168.9~
fe·murr rrenjeevlum
100
101
Fm Md
[257)
·2~81
ytterJlum
70
Yb
-7~_04
nobeliun
102
No
12591
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