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OCH701S - ORGANIC CHEMISTRY 2 - 1st Opp - JUNE 2022 |
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1.1 Page 1 |
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NAMIBIA UNIVERSITY
OF SCIENCE AND TECHNOLOGY
FACULTY OF HEALTH, APPLIED SCIENCES AND NATURAL RESOURCES
DEPARTMENT OF NATURAL AND APPLIED SCIENCES
QUALIFICATION: BACHELOR OF SCIENCE
QUALIFICATION CODE: 07BOSC
LEVEL: 7
COURSE CODE: OCH701S
COURSE NAME: ORGANIC CHEMISTRY 2
SESSION: JUNE 2022
PAPER: THEORY
DURATION: 3 HOURS
MARKS: 100
FIRST OPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S) DR. MARIUS MUTORWA
MODERATOR: DR. RENATE HANS
INSTRUCTIONS
Answer ALL the questions.
Write clearly and neatly.
Number the answers clearly
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
PERMISSIBLE MATERIALS
Non-programmable Calculators
ATTACHMENTS
NMR and IR Spectral Data, pKa Chart and Periodic Table
THIS QUESTION PAPER CONSISTS OF 14 PAGES (Including this front page)
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1.2 Page 2 |
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SECTION A
[50]
QUESTION 1: Multiple Choice Questions
[50]
e@ There are 25 multiple choice questions and each question carries 2 marks.
e Answer ALL questions by selecting the letter of the correct answer.
e Choose the best possible answer for each question, even if you think there is
another possible answer that is not given.
1.1 For the functional group(s) on the following molecule, what characteristic IR absorption(s)
would be expected (ignoring C-H absorptions)?
oeCOsH
A. Peaks around 1700 and 1650 cm?
B. A strong broad peak over 3600 to 2500 and around 1710 cm
C. Peaks around 1650 and 3300 cm}
D. Peaks around 3300 and 1710 cm
1.2 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. CH;3MgBr
b. H30*
A. A peak around 1710 cm™ would disappear and a new peak around 3300-3500 cm™ would
appear.
B. A peak around 1710 cm would appear and a new peak around 1650 cm‘! would disappear.
C. A peak around 2150 cm would disappear and a new peak around 3300-3500 cm would
appear.
D. No change would be observed.
1.3 Which of the following is not a prominent peak in the mass spectrum of 2-methyl-2-pentanol?
A. M-15
B. M-18
C. M-29
D. M-16
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1.3 Page 3 |
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1.4 Which
molecular
formula
is consistent with the following mass spectrum
M** at m/z= 72, relative height=73.0%
(M+1)** at m/z= 73, relative height=3.3%
data?
A. CaHi00
B. CaHoN
C. CsH12
D. CaHgO
1.5 How many signals would you expect to find in the 1H NMR spectrum of the following
compound?
A.5
B.6
G7
D.8
1.6 Which of the following is a correct prediction of the chemical shifts for the signals in the +H
NMR spectrum for the following compound?
I
IL
9
A. |=0.9 ppm, Il=1.7 ppm, IIl=3.9 ppm, IV=2.4 ppm
B. |=0.9 ppm, Il=1.2 ppm, IIl=3.7 ppm, IV=1.9 ppm
C. 1=0.9 ppm, Il=1.7 ppm, IIl=3.4 ppm, IV=2.4 ppm
D. |=0.9 ppm, Il=1.7 ppm, IIl=3.4 ppm, IV=1.9 ppm
1.7 Determine the number of singlet signals expected to be observed in the ‘H NMR spectrum of
the following compound.
0
:
A.2
B.3
C.4
D.5
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1.4 Page 4 |
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1.8 Provide the name of the compound below.
A
SQ
Se,
A. (3R,4E)-3-t-butyl-4-methyl-1,4-hexadiene
B. (3S,4E)-3-t-butyl-4-methyl-1,4-hexadiene
C. (3S,4Z)-3-t-butyl-4-methyl-1,4-hexadiene
D. (3R,4Z)-3-t-butyl-4-methyl-1,4-hexadiene
1.9 How many products are expected to be formed in the electrophilic addition reaction below?
HBr
A.2
B.3
C.4
D.5
1.10 Which one of the following dienophiles is least reactive in the Diels-Alder reaction?
O
O
CN
OCH3
NO.
—
OCH3
|
| H
J
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I
O
A. |
B. II
C. Il
D.IV
E.V
I
Ill
al
Vv
1.11 What is the !UPAC name for the following compound?
NO»
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A. 6-ethyl-3-nitrobenzoic acid
B. 1-ethyl-4-nitrobenzoic acid
C. 2-ethyl-5-nitrobenzoic acid
D. 2-ethyl-5-nitrobenzaldehyde
E. 4-nitro-3-carboxyethylbenzene
1.12 Which one of the following compound is nonaromatic?
4
O
Ss
le 4
B—CHs [
——
N
fv
I
A.|
B. Il
C. III
D.V
I
Il
1.13 Which of the following compounds is the most acidic?
A
RF Cc
8D
1.14 Arrange the compounds in order of increasing reactivity towards electrophilic substitution?
O
CNHCH;
A. Il, 1, IV, Il
B. I, III, IV, Il
C. III, 1, IV, I
D. IV, Ill, I, |
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1.6 Page 6 |
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1.15 Which is the best reaction sequence for preparing the following compound X from benzene?
O
C| wrOH
-
Cy NO>
xX
—AC_IHC=)C=?
AICk 3
ihe
O
a R‘HosCk or,Oz ee
° HNasO; 3
FySO4
Cc
_.
HN Oz
HaSO;
H—HNS—O0;>;
= AClHc> ,C
KH,=C S=O0,7
Az ICk 3
CHCl
HNO 3
SO;
D
Ko2 CnIOVF
H)SO.
A.A
B.B
GG
D.D
1.16 Which of the following statements is (are) true about electrophilic aromatic substitution?
A. The methoxy group is an ortho, para activator because of a strong electron donating effect
B. The methoxy group is an ortho, para director because of a strong electron withdrawing
inductive effect
C. The methoxy group is an ortho, para activator because the O atom is an electronegative atom
strong electron donating effect
D. Statement A (The methoxy group is an ortho, para activator because of a strong electron
donating effect) and Statement C (the methoxy group is an ortho, para activator because the O
atom is an electronegative atom strong electron donating effect) are the only true statements.
1.17 Both LiAIH4 and NaBHg are 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 LiAIHais 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 LiAIHa is 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 LiAIH, is the stronger reducing agent.
D. Both reagents contain polar metal-hydrogen bonas. The polarity of the B-H bond is less than
the polarity of the AI-H bond, so LiAIH, is the weaker reducing agent.
1.18 What is the IUPAC name for the following compound?
OH
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1.7 Page 7 |
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A. 5-sec-butyl-4,4-dimethyl-7-decanol
B. 6-sec-butyl-7,7-dimethyl-4-decanol
C. 4,4-dimethyl-5-sec-butyl-7-decanol
D. 7,7-dimethyl-6-sec-butyl-4-decanol
1.19 Which one of the following compounds gives 5-methyl-3-heptanol with LiAlH4 followed by
water?
oO
oO
SO
I
SO
H
li
A
|
Awa
|
peu
:
IV
Vv
A. |
B. Il
C. Il
D. IV
E.V
1.20 What is the IUPAC name for the compound below?
OH
O
A. 4-0xo-5-phenyl-2-hexanol
B. 2-hydroxypropyl-1-phenylethy! ketone
C. 5-hydroxy-2-phenyl-3-hexanone
D. 2-hydroxy-5-phenyl-4-hexanone
1.21 Predict the product for the following reaction.
OH
CH,0H = ——PC—C —, — exc>ess
CH,Cl,
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1.8 Page 8 |
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Ty
A. |
B. Il
C. Ill
D. IV
1.22 Provide the structure of the product, when cyclohexanecarbaldehyde reacts with excess 2-
propanol in presence of sulfuric acid.
ON
oan
oF |
ye
ay
iv
A. |
B. Il
C. Ill
D.IV
1.23 What is the IUPAC name of the following compound?
A
OH
A. 2-methylpentanoic acid
B. 3-methylpentanoic acid
C. 2-methylhexanoic acid
D. 3-methylhexanoic acid
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1.24 Rank the following acids in decreasing (strongest to weakest) order of acidity.
OC| OH
OC| OH
OC| OH
OC| OH
OCH;
NO»
CH2
Cl
A. Il>IV>II>1
B. III>IV>II>1
C. I>HI>IV>11
D. II>I>IV>III
1.25 Provide the reagents necessary to carry out the following conversion.
Br
a
OH
O
A. 1. Mg/ether; 2. CO2 and 3. H30*
B. 1. NaOH; 2. KMnOg/NaOH/H20 and 3. H30*
C. 1. NaCN and 2.H30*, heat
D. Aand C above
END OF SECTION A
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SECTION B:
QUESTION 2
What is (are) the product(s) of the following reactions?
Note: Each question carries 2 marks.
0|
COCH3
a
oO
NaBH, / H,0
—
O
1. excess LiAIHy
[ss oerenenEEEEEEEECaa
2. HO
b.
O
OH
we
|
excess
PCC/CH,Cl,
Cc.
CH20H
lCN|
‘| Cc —A
:
|Cc
C
HNO;/H2SO4
>
e.
[50]
[10]
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2 Pages 11-20 |
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2.1 Page 11 |
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QUESTION 3
[14]
Identify the lettered intermediates (A-G) in the following reaction sequence.
Note: 2 marks for each correct intermediate
{\\/-\\# + — FeBBri-.g
A
CH,COC!
AICI
HOCHCH2OH
H*
Cc
Mg
D
[1] CH,CHO
[2] HO
E
Pcc
F
HO
H*
G
QUESTION 4
[12]
Glutaraldehyde is a germicidal agent that is sometimes used to sterilize medical equipment.
In mildly acidic conditions, glutaraldehyde exists in a cyclic form as shown below. Draw a
stepwise detailed reaction mechanism for the reaction below.
oooO
Oe
JoO yO et
N[ O y |
COantDee ah me pe oymyt EVdA cog Elfhleloyp eg eed oo2“4
QUESTION 5
[14]
What is the structure of the compound with molecular formula C9H1003, IR absorptions at
3250 cm, 1680 cm™ and 1280 cm and has the following *H NMR data?
Signal #
|
2
3
4
5
Shift (ppm)
L.1
4.0
6.9
8.0
10.2
Multiplicity
triplet
quartet
doublet
doublet
singlet
Proton Ratio
3
2
2
2
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THE END
GOODLUCK
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2.2 Page 12 |
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1H NMR SPECTRAL DATA
Type of proton
|
on GH |
Characteristic Chemical
Ghemical shift (ppm)
Q.9-2
Shifts of Common Types of Protons
Type of proton
Chemical shift (ppm)
‘‘. C=C é H
fsope /f \\
4.5-6
e RCHs
~0.9
e* RRa,CCHHs
~~11.73
[>
\\or4“)
6.5-8
poe
i
Z=C.0,N
—C=C-H
bn
Sp a” ZL
Z=N.0.X
972.8
~2.5
2.54
Ro&y
f
R Se OH
RO-H
or R-N|-H
3-10
10-12
7-5
Bond type
O-H
N-H
G-H
® C.:-H
e C.2-H
®* ©.,-H
GEC
GN
C=O
C=C
ae Se 5
oe
Important IR Absorptions
Approximate ¥ (cm7}
3600-3250
3500-3206
~3000
3000-2850
3750-3900
33900
2250
2250
1800-1650 (often ~1700}
1656
1600, 1500
intensify
strong, broad
medium
strong
medium
medium
medium
medium
strong
medium
mediurn
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2.3 Page 13 |
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ia
a)
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2.4 Page 14 |
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