 |
OCH701S - ORGANIC CHEMISTRY 2 - 2ND Opp - JULY 2022 |
|
|
1 Pages 1-10 |
▲back to top |
|
|
1.1 Page 1 |
▲back to top |
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: JULY 2022
PAPER: THEORY
DURATION: 3 HOURS
MARKS: 100
SUPPLEMENTARY / SECOND OPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S) | DR. MARIUS MUTORWA
MOpERATOR; | 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)
|
|
1.2 Page 2 |
▲back to top |
SECTIONA
[50}
QUESTION 1: Multiple Choice Questions
[50]
@ 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)?
HO
A. Peaks around 1700 and 1650 cm?
B. Peaks around 3300 and 1710 cm?
C. Peaks around 1650 and 3300 cm?
D. Only a peak around 3300 cm
1.2 Which one of the following compounds will have the lowest wavenumber for carbonyl
absorption?
O
O
9
NH
O
0
I
I
|
II
III
IV
Vv
tl
IV
Vv
1.3 Which of the following is true about the molecular weight and the M**-m/z value for the
following compound?
Cl
ACA
A. odd molecular weight, m/z-115
B. odd molecular weight, m/z-121
C. even molecular weight, m/z-96
D. even molecular weight, m/z-132
Page 2 of 14
|
|
1.3 Page 3 |
▲back to top |
1.4 Which one of the following compounds is consistent with the mass spectrum below?
100 4
NS-Nw-Os33
80 —
60 5
40-4
20
4 et ttat ll
ttt Luk ttt
A. CH3CH2CH(CHs3)z2
B. CH3CHOHCH2CH3
C. CH3CH20CH2CH3
D. CH3CH2NHCH2CH3
1.5 How many signals would you expect to find in the 7H NMR spectrum of the following
compound?
Cl
A.5
B.6
C.7
D.8
1.6 Which
of the
following
protons appear
Ha I
most upfield in the 17H NMR
aI
Z
SS
spectrum?
AW
A.|
B. Il
C. III
D. IV
1 eH
Page 3 of 14
|
|
1.4 Page 4 |
▲back to top |
1.7 Which of the following compounds will display a singlet, a triplet and a quartet in the 1H NMR
spectrum?
A. 2-chloro-4-methylpentane
B. 3-chloro-2-methylpentane
C. 3-chloro-3-methylpentane
D. 1-chloro-2,2-dimethylbutane
1.8 Which one of the following dienes will have the highest heat of hydrogenation?
aren
a
yy
Sy
]
A.|
B. Il
C. Ill
D. IV
E.V
:
I
IV
¥
1.9 What is the IUPAC name for the following compound?
QDS
A. (2E,4Z,6E)—-3,4,7,8-tetramethyl-2,4,6—heptatriene
B. (2Z,4E,6E)—3,4,7—-trimethyl-2,4,6—octatriene
C. (2E,4Z,6E)— 2,5,6—-trimethyl-3,5,7—octatriene
D. (2E,4E,6E)—2,5,6—-trimethyl-2,4,6—octatriene
oo cogG 1.10 Which of the following diene(s) can not undergo the Diels-Alder reaction?
A. |
B. Il
C. Ill
D.IV
E. | and IV
. Page 4 of 14
|
|
1.5 Page 5 |
▲back to top |
1.11 What is the IUPAC name for the following compound?
A. 6-ethyl-4-fluoro-3-methylbenzaldehyde
B. 2-ethyl-4-fluoro-5-methylbenzaldehyde
C. 1-aldehyde-2-ethyl-4-fluoro-5-methylbenzene
D. 2-ethyl-4-fluoro-1-formyl-5-methylbenzene
1.12 Which one of the following compounds is aromatic?
Gi relelH e
A.|
B. Il
C. Ill
D. IV
1.13 Which of the following alkyl halides reacts the fastest in an SN1 reaction?
1.14 Predict the major product for the reaction between benzene and 2-chlorobutane in the
presence of AICl3.
A. t-butylbenzene
B. sec-butylbenzene
C. ethylbenzene
D. isopropylbenzene
Page 5 of 14
|
|
1.6 Page 6 |
▲back to top |
1.15 Arrange the following compounds in order of decreasing reactivity towards electrophilic
aromatic substitution:
as
Cl
O
H
OH
}
I
Il
0
IV
V
A. V>II>I>1I>1V
B. II>V>III>1>1V
C. IV>I>HI>V>lI
D. II>I>1>IV>V
1.16 Predict the major product for the following reaction.
"Scoci,
ON 66EH,
Scoch; — O Scochs
O Sscoch;
NO»
HINOy H;80.-
NO»
NO»
Ill
IV
A. |
B. Il
C. Ill
D.IV
1.17 What is the IUPAC name for the following compound?
A. 4-penten-2-methyl-2-ol
B. 4-methyl-1-penten-2-ol
C. 2-methyl-4-penten-2-ol
D. 4-methyl-1-penten-4-ol
E. 4-hydroxy-4-methyl-1-pentene
Page 6 of 14
|
|
1.7 Page 7 |
▲back to top |
1.18 Which one of the following alcohols is most acidic?
0
OH
O
OL
°
I
Il
A.|
B. Il
C. Ill
D. | and Ill are equal
: “OH
Ill
1.19 Provide the reagents necessary to carry out the following conversion.
OH
AOA
————>pee
A. NaOH/H20
B. 1. NaOCHs, 2. H30*
C. 1. (CH3)3COK, 2. BH3, 3. H202/NaOH/H20
D. 1. (CH3)3COK, 2. H30*
1.20 What is the IUPAC name for the following compound?
O
A. 2,4-dimethyl-2-pentenone
B. 2-methyl-5-methylcyclopent-2-enone
C. 3,5-dimethylcyclopent-2-enone
D. 2,4-dimethylcyclopent-2-enone
Page 7 of 14
|
|
1.8 Page 8 |
▲back to top |
1.21 Compound A on ozonolysis yields acetophenone and propanal. What is the structure of
compound A?
Compound A
21.. (O3CHy 5
Acetophenone + propanal
A. 2-phenyl-2-pentene
B. 1-phenyl-1-hexene
C. 1-phenyl-2-pentene
D. 2-phenyl-2-hexene
1.22 Which one of the following compounds gives 5-methyl-3-heptanol with LiAlHa followed by
SO i
A.|
B. Il
C. Ill
D.IV
1.23 What is the IUPAC name of the following compound?
)
|
O
H3;C~ ~CH,-CH,-CH,-C—OH
A. 2-oxohexanoic acid
B. 5- oxohexanoic acid
C. methyl butyroxo ketone
D. 4-ketopentanoic acid
1.24 Rank the following acids in decreasing (strongest to weakest) order of acidity.
0
oO
O
A.
13
a.
la
SA
nr
Oo
IV
HL Br
O
aco
Vv
Page 8 of 14
|
|
1.9 Page 9 |
▲back to top |
A. V>III>I>11>1V
B. II>I>II>V>1V
C. IV>II>1>1>V
D. IV>V>III>I>II
1.25 Predict the product for the following reaction.
1. LIAIH,
2. HO$$ >
HOW
i
B
oN
c.
A.A
B.B
C.C
D.D
END OF SECTIONA
Page 9 of 14
|
|
1.10 Page 10 |
▲back to top |
SECTION B:
QUESTION 2
What is (are) the product(s) of the following reactions?
Note: Each question carries 2 marks.
|
COCH,
a
0
1. LiAIHy
2. H,0 _—_—_—_—_—
excess
>
O
1. CH;CH,MgBr
$$$
2. HO
b.
A
Cc.
OH
Kk
NazCr207/H»SO,4/H,0
KS
SS
i—~ OH
A
+
|
a
a OH
d.
0
|
COCH3
(CH3)3CCl
a
AICI;
e,
OCH3
[50]
[10]
Page 10 of 14
|
|
2 Pages 11-20 |
▲back to top |
|
|
2.1 Page 11 |
▲back to top |
QUESTION 3
[12]
Identify the lettered intermediates (A-F) in the following reaction sequence.
Note: Each question carries 2 marks.
¢i /f fF,
‘
\\PHCH,
[1] BH3 =
A
CrO3
B
a.
\\
f
[2] HoOp, HO-
HsSO., H>O
HC=CH
—[[12]]
NaNH>
CHgl
b.
c
[1]
[2]
NaNH>
CHaCH3I
>
D
[1] O;
[2] H2O
E+F
QUESTION 4
[13]
Draw a stepwise detailed reaction mechanism for the intramolecular reaction below.
| os | +
vs ae
" o eH,s80,s
hn
Ne f
Sig[|e |
*
ge Ss alll
f
NY
+ H,0
QUESTION 5
[15]
An unknown compound A has the molecular formula Ci2HisO. A absorbs strongly in the IR at
1715 cm?. The +H NMR spectral data for A are given below. What is the structure of A?
absorption
| ppm
singlet
1.0
triplet
/ 12
bqruoaartdestinglet 2720
ratio oi absorbing H’s
6
3
[383
THE END
GOODLUCK
Page 11 of 14
|
|
2.2 Page 12 |
▲back to top |
1H NMR SPECTRAL DATA
Type of proton
Characteristic Chemical
Chemical shift (ppm)
0.9-2
Shifts of Common Types of Protons
Type of proton
Chemical shift (pprn)
\\ cae Da
f‘sp=i \\
4.5-6
0.9
—
1.1.73
\\ \\ 4 pi
6.5-3
-5-2.5
~2.5
2.5-4
&
R™ HH
oO
JL.
R™ ~OH
RO-H- or aes
10-12
Bond type
O-H
N-H
C-H
Important IR Absorptions
Approximate ¥ (cm)
3600-3206
3500-3206
~3C600
3000-2850
3750-3900
3300
2250
2250
1800-1650 (often ~1700}
1650
1600, 1506
intensity
strong, broad
medium
strong
medium
medium
medium
medium
strong
medium
medium
Page 12 of 14
|
|
2.3 Page 13 |
▲back to top |
oka
|
|
2.4 Page 14 |
▲back to top |
