f_HHITIIBIH Ul'llVERSITY

OF SCIENCE HHD TECHI'IOLOGY

FACULTY OF HEALTH AND APPLIED SCIENCES

DEPARTMENT OF NATURAL AND APPLIED SCIENCES

QUALIFICATION: BACHELOR OF SCIENCE

QUALIFICATION CODE: O7BOSC LEVEL: 7

COURSE CODE: OCH701S COURSE NAME: ORGANIC CHEMISTRY 2

SESSION: JUNE 2017 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 clearlyPWF’!‘ All written work must be done in blue or black ink and sketches can

be done in pencil

5. No books, notes and other additional aids are allowed

PERMISSIBLE MATERIALS

Non-programmable Calculators

ATTACHMENTS

IR and 1H NMR Spectral Data, pKa Chart and Periodic Table

THIS QUESTION PAPER CONSISTS OF 15 PAGES

(Including this front page, IR and 1H NMR Spectral Data, pKa Chart and Periodic Table)

SECTION A [50]

QUESTION 1: Multiple Choice Questions [50]

0 There are 25 multiple choice questions in this section. Each question carries 2 marks.

0 Answer ALL questions by selecting the best possible answer for each question, even ifyou

think there is another possible answer that is not given.

1.1 Which of the following is not a resonance structure of the species A shown?

.. e

..I. NHg 111- NH2

NH2 E

H H

o 11. NH2 IV- NH2

A. I

B. 11

C. III

D. IV

1.2 In which of the following does resonance delocalization of electron density n_ot play a role?

A. Allyl cation

B. Benzyl anion

C. Carbonate anion

D. Ozone

E. Cyclohexyl radical

1.3 Which of the following is aromatic?

A. Cyclopentadienyl cation

B. 1,3—cyclohexadiene

C. Cyclobutenyl cation

D. 1,3,5-hexatriene

E. 1,3,5-Cycloheptatrienyl cation'

Page 2 of 15

1.4 Which of the following statements about the n molecular orbital description of cyclobutadieneis not correct?

A. Cyclobutadiene has a single bonding TI molecular orbital.

B. Cyclobutadiene has two electrons in nonbonding It molecular orbitals.

C. Cyclobutadiene has one electron in an antibonding rt molecular orbital which makes it anti-

aromatic.

D. None of the above

1.5 Treatment of the diene below gives a mixture of products. Predict the major product under the

given conditions.

H—Br___._>

150°C

BrBr

IBr

Br

B C DA

A.A

B.B

C.C

D.D

1.6 Which of the following is a correct statement considering thermodynamic versus kinetic control

of organic reactions?

A. When a reaction is under thermodynamic control, the relative amounts of products dependon the activation energies of the steps leading to their formation.

B. The kinetic product always predominates when the reaction is reversible.

C. Higher temperatures and longer reaction times typically favor the kinetic product over the

thermodynamic product.

D. When the products are in equilibrium under the reaction conditions, the relative amounts of

products depend on their stabilities and the reaction is under thermodynamic control.

E. None of the above

Page 3 of 15

1.7 Arrange the compounds in order of increasing reactivity toward electrophilic aromatic

substitution.

$5335I H [[I IV

A. III, II, I, IV

B. IV, II, I, III

C. III, I, II, IV

D. I, II, III, IV

1.8 What is the major organic product of the reaction between benzene and isobutyl chloride in the

presence of AICI3?

A. tert-butylbenzene

B. isobutylbenzene

C. n-butylbenzene

D. chlorobenzene

E. sec-butylbenzene

1.9 Choose the best reagent to carry out the reaction below?

*E—\ ——> /u\OH +

/\n/OHO

A. K2Cr207, H2504, H20

B. (1) 03, (2) H20

C. NaOH, H20

D. NaH

E. None of the above

Page 4 of 15

1.10 Which of the following fails to produce benzoic acid when heated in the presence of acidic

sodium dichromate?

A. 1-phenylethanol

B. Z-phenylethanol

C. 2-phenylheptane

D. 2-methyI-2—phenylheptane

E. 1-phenylheptanol

1.11 Which reagent would you use to reduce an alkene in cyclopentenone?

A. NaHB4

B. LiAlH4

C. 1 eq. H2 and Pd/C

D. FeC|3

E. DIBAL-H

1.12 Which is the best reaction sequence for preparing the following compound from benzene?

A1C13

Cu)COH

N09

Kath-207> HNO3

a) CH3CI>

HNO3——>

H2804

H

H3CC1

——>

CH3C1

———>

H2804 H2304

NClg, K2C1‘207——“—> ———)

HINO3———>

H2804

I—INO3 K2C1'207——> ———>

H2804 H2304

Page 5 of 15

1.13 What is the structure of the final product resulting from the sequence of reactions shown

below?

0

1. Fe, HCl

0OCH3 2 A

__.—> ?

D 3. LiAlH402N

4. H20OH O

oN.

A. B. C. D.

A.A

B.B

C.C

D.D

1.14 Which is the best method for making the following conversion?

oHCH3CH2CHZOH ——> CH3CHCH3

H PO'

Pt/H‘

a)3 4 d11ute

b)2 d11ute

heat H2804 191st4

f.’

H PO @Co‘mc) P_CC_, d) 3—1» __>

heat

1.15 Why are strongly acidic conditions not used in the formation of enamines and imines?

A. The carbonyl will be protonated

B. The amine will be completely protonated

C. The product is not stable to strong acids

D. An enol will be formed

E. The carbonyl and amine will both be protonated

Page 6 of 15

1.16 Treatment of cyclopentene with dilute sulphuric acid, followed by reaction with chromic acid

gives which of the following compounds as the major product?

OH O

O

a) 0/ b) 0H c) 0:0 (1) _0

1.17 The formation of a kinetic enolate is favoured by:

A. Using a strong, non-nucleophilic base such as LDA

B. using a protic solvent

C. keeping the reaction temperature low

D. both using a strong, non-nucleophilic base such as LDA and keeping the reaction temperature

low

E. both using a strong, non-nucleophilic base such as LDA and using a protic solvent

F. both using a protic solvent and keeping the reaction temperature low

1.18 Select the structure of the product in the following reaction.

1. Ph3P

2. KOtBu

—__>

3. 0&0

W 0% GM 08k

/\/\Br

A.A

B.B

CC

0.0

Page 7 of 15

1.19 Which of the following functional groups typically exhibits a carbonyl stretch at the lowest

frequency?

A. Amide

B. Ester

C. Ketone

D. Aldehyde

E. Carboxylic acid

1.20 An increase in conjugation is correlated with in the energy of the LUMO,

in the energy of the HOMO, and in Amax-

A. a decrease, an increase, a decrease

B. a decrease, an increase, an increase

C. an increase, a decrease, a decrease

D. an increase, a decrease, an increase

E. an increase, an increase, a decrease

1.21 What is the correct IUPAC name for the following compound?

0

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

E. 1,1,3-trimethanal—2,4-cyclohexadiene

1.22 The formation of a thermodynamic enolate is favoured by:

A. keeping the reaction as cold as possible

B. using an aprotic solvent, such as THF

C. using a protic solvent, such as ethanol

D. using a carboxylic acid

Page 8 of 15

1.23 What are the three steps in the malonic ester synthesis, listed in the correct order?

A. Deprotonation, alkylation, hydrolysis/decarboxylation

B. Hydrogenation, alkylation, deprotonation

C. alkylation, hydrolysis/decarboxylation, hydrogenation

D. hydrolysis/decarboxylation, deprotonation, alkylation

1.24 Under basic conditions, the aldol reaction is reversible, but dehydration is not. Why?

A. Formation of the a, B-unsaturated carbonyl product from dehydration is energetically

favourable.

B. Formation of the B-hydroxy carbonyl product from dehydration is energetically favourable.

C. Formation of the saturated carbonyl product from dehydration is energetically favourable.

D. Water as a product is more stable

1.25 How would you perform a mixed—aldol reaction below to obtain the product selectively?

{5.91.1A. First add sodium methoxide to propanal then add cyclopentanone

OH

B. Use potassium tert-butoxide to catalyse the reaction

C. Use acetic acid to catalyse the reaction

D. First add lithium diisopropylamide to cyclopentanone and then add propanal

Page 9 of 15

SECTION B:

QUESTION 2

[50]

[1 0]

What is the major product of the following reactions? Include stereochemistry where necessary.

Note: Each question carries 2 marks.

O NaOCH3H,,

A. ’- ———>

CH3OH

002Me

“N

8- cs ———»

cKMnO4

O NH

D.—>

Mild acid,heat

OO O

E.

NaO/\

2. HCl, A

Page 10 of 15

QUESTION 3 [12]

Identify the lettered compounds (A — F) in each of the following reaction sequences.

Note: Each question carries 2 marks

1 BH CrO

[2] H202, HO‘ H2304, H20

1NNH 1NNH 10[132 C[]a2 D[13

b. HC‘=‘CH-———-—> ———> ———> E + F

[2] CH3] [2] CHaCHzl [2] H20

QUESHON4 B]

Identify the lettered reagents (A— D) needed to achieve the transformations in the followingreaction sequence.

COOH

0 Ho CECH #3146ng[11A

pngo

'__—

DH: §iQUESHON5 pm

Treatment of Compound W below with CHaLl, followed by CH3I, produces compound Y as the major

product, with Molecular Formula C7H14O. Compound Y shows a strong absorption in its IR spectrum

at 1713 cm‘1 and its 1H NMR spectrum is given below.

0

)l\O [1] CHaLi

/ [2] CH31

W

Page 11 of 15

1H NMR on

1H

3 Jim‘.

‘lL

2H6H

\L

8""l""%"'llill'élllll"l'é'llll'll'4l’""I'l'lé'I'lllll'é‘lllll'lllli‘IIH"

ppm

a. Propose a Structure for Compound Y.

1

b. Draw a detailed stepwise mechanism for the conversion of compound W

to compound Y.

THE END

GOODLUCK

O

(12)

(8)

Page 12 of 15

1H NMR SPECTRAL DATA

Characteristic Chemical Shifts of Common Types of Protons

Type of proton Chemical shift (pom)'

'

_

iipr of proton Chemical shift (ppm)

H

é H 09_2 >cjc< 4.5—6

Spa/I Spa

. RCHa ~0.9

. FizCHz ~1.3 0H 6.5-8

. RSCH ~1.7

2“(3 cl: H 1 5—2 5 (I)/ l

‘ '

R/QH 9—10

Z = C, O, N

‘1?—CEC—H ~2 5 /C\ 10—12

H OH

742—14 2.5—4

sp3 ZRO~‘H or

Fi—iTI-H1—5

Z = N, O X

important IR Absorptions

Bond typew Approximate? (031") intensity

0 — H 3600—3200 strong, broad

N - H 3500—3200 medium

0— H ~3000

. Csps- H 8000—2850 strong

0 0502— H 3150—3000 medium

. Cin- H 3300 medium

CE C 2250 medium

CE N 2250 medium

C = 0 1800—1650 (often ~1700) strong

0: C 1650 medium

© '

1600, 1500 medium

“0.431;...“ n.2,”--.- dun, .e , ._ '.

Page 13 of 15

sulfuricacid

H2304

—""H804—

hydroiodicacid

H!

—>

[—

hydrobromicacid

HBr

———>

Br

hydrochloricacid

HCI:

i

:9.”

H

carbocationsA)

—’.+

M

pl‘otonated

.

.

H

H

alcohol

Ag);

/\bv

hydroniunlion

H

nitricacid

HNO3

—’*N03

hydrofluoricacid

HF

—>-F

pKaChart

-10

hydrogencyanide

phenols

-7

water

.3

primaiyalcohols

alkynes

‘1'7

hydrogen ammonia/amines

alliancs

con'uoate

acid

con'uoatebase

H—CENI—r-TCEN:

9-1

CEO—H

—>~

(cyanide) —;§_H

15.7

(hydroxide) A5?

16

(alkoxidds) CEC:_

26

(acetylideanions)

3H

(hydride)

35

.Q

R’-N-\

H

36

(amidebases)

A:

~60

hydrcgen 1 H 1.0079 lithium 3 Li 6941

helylllJm 4 Be 9.3122

ssdiJm 11 Na 22.890

magieslum 12 Mg 24.305

p0:asslurn 19 K39.098

cdcium 20 Ca 4

0.

078

rubidium 37 Rb 55.468

slmnliJm 38 Sr 87.62

helzurr He 4.0026

130101 5 B 10.811

canon 6 C 1201'

nitrogen 7 N 14.007

oxygen 8 O1

5.999

fluonne 9 F 18999

Dian Ne 20.180

sluminlun‘ 13 AI 26.952

silieor 14 Si 28.086

phcsphorus 15

p 30.974

sulfur 16 S 32.065

chlsrine 17

CI

35453

argon 18 Ar 39.948

scandium 21 Sc 44.956

lllaniJm Ti 47.867

vamd‘um 23 V 50.942

cwrmlium

mmganE56

24

25

Cr

Mn

51

.996

54.

935

'11—? Fe 55.845

cobalt 27 Co 58.933

nicke Ni 58.693

(Diner 29 Cu 63.546

Zil’i: 30 Zn 65.39

gdliU'n 31 Ga 69.723

germanium 32 Ge 72.61

a’senlc 33 As 74.

922

selen'um 34 Se 78.56

Dl’Cl'iiil'Ie 35 Br 79.904

krypton 36 Kr 8380

{IiiiUIT 39 Y 88.906

zir:onium 40 Zr 91.224

niohiLm 41 Nb 92.906

mclybdenuntechnetium 43

Mo

Tc

95.94

L931

ruhenium 44 Ru 101.07

rhodiLm 45 Rh 1C2.E1

palladiLm 46 Pd 106.42

silver 47 Ag 107.87

cadmum

48 Cd 112.41

indIu

m

49 In 114.82

£3 Sn 118.7‘

artirrony 51 Sb 121

76

ieiuriJm 52 Te 127.50

iodine 53 126.50

xenon 54 Xe 131.29

caesU111

55 Cs 132.91

bariLm 56 Ba 137.33

57-70

lulezlun 71 Lu 174.97

hafniurr 72 Hf 178.49

ianlalum 73 Ta 180.95

lJngslen

rherlun

74

75

WRe 183.84

”86.21

osmlJm 76 Os 190.23

iridium 77 Ir 192.22

piainu‘n 78 Pt 195.08

gdd 79 Au 196.97

mercury 80 H9 200.59

thallium 81 TI 204.28

Pb 207.2

b

srruir Bi 20898

pobniurr 84 P0 [209]

aslaline 85 At [210'

racon 86 Rn [222]

irandum 87 Fr [223]

radle 88 Ra 1226i

39.102 *-X-

Iawrenclum

103 Lr [262]

ruiherfnrdiJm 104 Rf '261]

dubnium 105 Db [262]

8890079um

bonriun

106

107

$9

Bh

[256]

[264]

hassiurr 108 Hs 1269]

meiheiium 109 Mt 12681

ununnllium 110 Uun [271]

ununLniLm 111 Uuu 1272]

ununtlum 112 Uub 12771

*Lanthanideseries

**Actinideseries

Jnanuadum 114 Uuq [289]

lanthanum 57 La 138.9'

cerium 58 Ce 14012

praseadymium 59 Pr 11.0.91

neodymium

promeihiJm 61

Nd

Pm

144.24

[145]

sama'ium 62 Sm 1

50.36

eurapiJm 63 Eu 151.96

gadoliniJm 64G

(1

15’23

lerbiuni 65 Tb ’

58.93

dysarosium 66 Dy1

52.50

holmium 67 Ho 164.93

ertium 68 Er 167.26

ihuiiurr 69 Tm 168.93

yiierbium 70 Yb 173.34

Eclinlum 89 Ac [227i

tnor‘um 90 Th 23204

pioiacli'IIU'n 91 Pa 231.04

Jranium

nepiLniLm92 UNp 233.03

[2371

DILiOiiiUm 94 Pu '244]

amerlciu1'11

95 Am [1’43]

cunun 96 Cm 1247]

berkellun 97 Bk [2‘71

061110111Ium

98 Cf 1251]

ensteiriun 99 Es [2521

iermlum 100 Fm [2571

merde8Vurr

101 Md [258]

[10361um

102 No 12591

Page15

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