ORC601S - ORGANIC CHEMISTRY 1 - 1ST OPP - JUNE 2023 :: NUST past examination papers between 2020 and 2024

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ORC601S - ORGANIC CHEMISTRY 1 - 1ST OPP - JUNE 2023

1 Pages 1-10

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2 Pages 11-20

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2.2 Page 12

ORC601S - ORGANIC CHEMISTRY 1 - 1ST OPP - JUNE 2023

1 Pages 1-10

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1.1 Page 1

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nAm I BI A u n I VE RS ITY

OF SCIEnCE Ano TECHnOLOGY

FACULTYOF HEALTH, APPLIEDSCIENCESAND NATURAL RESOURCES

SCHOOL OF NATURAL AND APPLIED SCIENCES

DEPARTMENT OF BIOLOGY, CHEMISTRY AND PHYSICS

QUALIFICATION: BACHELOR OF SCIENCE

QUALIFICATION CODE: 07BOSC

LEVEL: 6

COURSE CODE: ORC601S

COURSE NAME: ORGANIC CHEMISTRY 1

SESSION:

JUNE 23

PAPER:

THEORY

DURATION:

3 HOURS

MARKS:

100

EXAMINER(S)

FIRST OPPORTUNITY EXAMINATION QUESTION PAPER

DR. MPINGANA AKAWA

MODERATOR: PROF. HABAUKA KWAAMBWA

INSTRUCTIONS

1. Answer ALL the questions.

2. Write clearly and neatly.

3. Number the answers clearly.

PERMISSIBLEMATERIALS

1. Non-programmable Calculators

THIS QUESTION PAPER CONSISTS OF 13 PAGES (Including this front page)

1.2 Page 2

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SECTION A

QUESTION 1: Multiple Choice Questions

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

• Answer ALL questions by selecting the letter of the correct answer.

[SO]

1.1 Which of the following alkanes would have the lowest boiling point?

A. CH3CH2CH2CH2CH2CH2CH3

B. (CH3)3CCH(CH2)2

C. CH3CH2CH2CH2CH(CH3)2

D. (CH3)2CHCH2CH(CH2)2

1.2 Consider the following acid-base reaction. The equilibrium for this reaction lies to the:

H3C-CHrc=c:

A. Left

B. Right

C. It cannot be determined

D. The forward and reverse reactions are equally favoured

1.3 Which of the following is not a nucleophile?

A. ·cN

B. CH3NH2

C. CH3Q·

D. H20

E. +N02

1.4 Consider the three isomeric alkanes n-hexane, 2, 3-dimethylbutane, and 2-methylpentane.

of the following correctly lists these compounds in order of increasing boiling point?

A. 2, 3-dimethylbutane < 2-methylpentane < n-hexane

B. 2-methylpentane < n-hexane < 2, 3-dimethylbutane

C. 2-methylpentane < 2, 3-dimethylbutane < n-hexane

D. n-hexane < 2-methylpentane < 2, 3-dimethylbutane

Which

1.5 Among the butane conformers, which occur(s) at energy minima on a graph of potential energy

versus dihedral angle?

A. gauche only

B. eclipsed and totally eclipsed

C. gauche and anti

D. eclipsed only

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1.6 Which of the following compounds in the product of catalytic hydrogenation of 2,3-Dimethyl-2-

butene?

A. 2,3-Dimethylbutane

B. 2-Methylpentane

C. 2,2-Dimethylbutane

D. 3-Methylpentane

1.7 What is the IUPAC name of the following compound?

C:l-13C- CC:H2C(CH3l3

A. 4,4-dimethyl-2-hexyne

B. 5,5-dimethyl-2-hexyne

C. 5,5-dimethyl-3-hexyne

D. None of the above

1.8 What is the correct name of the following compound?

A. 3-methylbenzoic acid

B. m-methylbenzoate

C. tolylcarboxylate

D. methylbenzoate

1.9 Markovnikov addition of HBr to 1-propene involves:

A. Initial attack of bromide ion

B. Initial attack of bromine radical

C. Formation of a secondary carbocation

D. Formation of a primary carbocation

0: o+ u Cf 1.10 Which of the following carbocations is the most stable?

A. A

B. B

C. C

D. D

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(!OH 1.11 How many stereogenic centres are present in the following compound?

~OH

A. 0

B. 1

C. 3

D. 4

E. 5

1.12 Which of the following is a product of the acid-catalyzed hydration of 3-methyl-2-

pentene?

A. 2-methylpentane

B. 3-methyl-1-pentanol

C. 3-methyl-3-pentanol

D. 2-methyl-2,3-pentadiol

1.13 What is the molecular geometry of the central atom in CH30(H3?

A. Trigonal planar

B. Trigonal pyramidal

C. Tetrahedral

D. Bent

1.14 Which of the following statements is true in comparing ethane, ethene and ethyne to

one another?

A. Ethyne is the weakest acid and has the longest C-H bond distance.

B. Ethyne is the strongest acid and has the shortest C-H bond distance.

C. Ethane is the strongest acid and has the longest C-H bond distance.

D. Ethene is the strongest acid and has the shortest C-H bond distance.

1.15 Which of the following anions is the best leaving group?

A. NH2-

B. c1-

C. CH3-

D. OW

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1.16 What is the condensed formula of the compound below?

A. CH3CH2CH(CH3)CH2CH(CH3)CHBr2

B. CH3CH2CH2(CH3)CH2CH(CH3)CHBr2

C. CH3CH2CH(CH3)CH(CH3)CH2CHBr2

D. None of the above

1.17 Give the IUPAC name for the following compound.

rl Br\\

Cl~\\

A. (Z)-1-bromo-2-chloro-2-ethyl-4-methyl-1-pentene

B. (E)-1-bromo-1-chloro-2-ethyl-4-methyl-2-pentene

C. (Z)-1-bromo-1-chloro-2-ethyl-4-methyl-1-pe ntene

D. (E)-1-bromo-1-chloro-2-ethyl-4-methyl-1-pentene

1.18 What is the nucleophilic site in each of the following molecules?

A. A: hydrogen; B: nitrogen; C: 2 electrons in bond

B. A: oxygen: B: nitrogen: C: carbon

C. A: oxygen; B: nitrogen; C: 2 electrons in bond

D. A: oxygen: B: carbon; C: 7 electrons in bond

1.19 The formal charge on the nitrogen atom in the nitrate ion, NO3-, is [2]

A. -3

B. 0

C. +1

D. +3

E. +5

1.20 Which molecule has a nonzero dipole moment?

A. Cb

B. CO2

C. CCl4

D. CHCl3

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1.21 Using Markovnikov's rule, predict the position of the Cl atom in the major product from

the reaction of 1-methylcyclohexene with HCI.

A. A

B. B

C. C

D. D

1.22 Which of the following reagents must be used with HBr to convert 1-hexene to 1-

bromohexane?

A. HS03-

B. NaBH4

C. ROOR

D. Pd/C

E. no other reagent is necessary

1.23 Which of the following compounds consists of only sp3 hybrid carbon orbitals?

A. CH3CH2CH3

B. CH3C:CH

C. CH3CH=CH2

D. CH2=CH-CH=CH2

1.24 Give the IUPAC name of the following compound.

CH3C( CH3)2CH2C CCI-hCI-f(CH2CH2CH3 )CH3

A. 2,2, 7-trimethyl-4-nonyne

B. 2,2, 7-trimethyl-4-decyne

C. 3,3, 7-trimethyl-4-decyne

o_ 2,2,6-trimethyl-4-undecyne

1.7 Page 7

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25. Which of the following statements is (are) true about the energy diagram drawn below?

reaction

A. The reaction mechanism has two steps

B. b labels a transition state.

C. The overall reaction is endothermic

D. The conversion of a to b is faster than the conversion of b to c.

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SECTION B

(50]

• There are SIX questions in this section. Answer all Questions.

QUESTION 2

(31

2.1 Which of the following alkanes would have the lowest boiling point? Explain.

A. CH3CH2CH2CH2CH2CH2CH3

B. {CH3)3CCH{CH3)2

C. CH3CH2CH2CH2CH{CH3)2

D. {CH3)2CHCH2CH(CH3)2

QUESTION 3

[10]

3.1 Give systematic IUPAC names or draw the skeletal structures of the following organic compounds

a) 5,5-dimethyl-2-hexyne

b) 3-ethyl- 4-methyl-2-pentene

c) 1,6,6-trimethylcylcohexa-1,4-diene

CJ13CI 11CTl1CI 11 "'

C=C

'-.. CH~CH10l 3

QUESTION 4

[6]

4.1 The names of the following compounds are not correct. Point out the errors and correct them.

a) 2,2-dimethyl-6-ethylheptane

b) 4-ethyl-5,5-dimethylhexane

c) 5,5,6-trimethyloctane

1.9 Page 9

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QUESTION 5

[4]

5.1 Classify each of the following reactions as addition, elimination, substitution or rearrangement.

(a) CH3CH2Br + NaCN

lblo --0 _./

-OH

Acid

catalyst

"CH3CH2CN( + NaBr)

( + H20}

(c)

ldlo

+ 02N-N02

or -Heat

UNO,

Light,

( + HN02)

QUESTION 6

6.1 The below equation shows the bromination of methane. Propose a radical reaction mechanism to

account for the product formation.

[7]

6.2 Consider the following equation:

[8]

Explain how the product is formed by showing a complete mechanism (show with arrows). Is

this a Markovnikov or Anti-Markovnikov product? Explain

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QUESTION 7

(12]

7.1 Predict the product(s) or the conditions of the following reaction

H:!0, H2S0:

Uc"l"'"c__,H(b)

(1) BH 3 :THF

(2) NaOH. H 2 02

UOCH3 (d)

(e)

(a)

(c)

o<CH3

/OH

Catalyst

(f)

END OF EXAMINATION QUESTIONS

2 Pages 11-20

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2.1 Page 11

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