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Chem 130: Organic Chemistry Question Paper
Chem 130: Organic Chemistry
Course:Bachelor Of Education Science
Institution: Chuka University question papers
Exam Year:2013
CHUKA
UNIVERSITY
UNIVERSITY EXAMINATIONS
FIRST YEAR EXAMINATION FOR THE AWARD OF DEGREE OF
BACHELOR OF EDUCATION (SCIENCE) AND BACHELOR OF SCIENCE
CHEM 130: ORGANIC CHEMISTRY
STREAMS: BED (SCI), BSC Y1S2 TIME: 2 HOURS
DAY/DATE: TUESDAY 6/8/2013 2.30 PM - 4.30 PM
INSTRUCTIONS:
Answer Question ONE and any other TWO Questions
Question One (30 Marks)
(a) Define the following terms
(i) Hybridization [2 marks]
(ii) Catenation [2 marks]
(iii) Functional group [2 marks]
(b) Distinguish between aliphatic and aromatic hydrocarbons. [2 marks]
(c) Briefly explain why branched alkanes boil at lower temperature than the straight chain alkanes. [2 marks]
(d) Provide a systematic (IUPAC) name for each of the following:
CH2CH2CH3
|
(i) CH3- CH- CH2-CH-CH2-CH3 [1mark]
|
CH3
(ii) H H [1 mark]
CH3 CH3
(iii) [1 mark]
Br
Br Cl
[1 mark]
(iv) C = C
CH3 H
(v) [1 mark]
(vi) CH3 - CH2 - C – CH3 [1 mark]
(vi) CH2 – CH2-CH2-NH2 [1 mark]
OH
|
(vii) CH3- CH –CH- CH3 [1 mark]
|
CH3
(viii) CH3 CH2 COOH [1 mark]
(ix) CH3 CH2CH2CHO [1 mark]
(e) Predict the products of the following reactions. When more than one product is possible, predict which will be major product.
(i) OH H2So4 (l) [1 mark]
heat
(ii) CH3 NaOCH3 [1 mark]
Br
CH3 H
(iii) C = C + HBr [1 mark]
H H
(f) For each of the following pairs of compounds, predict which compound has the higher boiling point.
(i) Isopropylbromide and n-butylbromide [1 mark]
(ii) CH3 CH2 CH2 OH and CH3 CH2 CH3 [1 mark]
(g) Explain why the compounds predicted in f(i) and f(ii) above have higher boiling point relative to the other in each pair. [4 marks]
(h) What is the major component of natural gas? [1 mark]
Question Two (20 Marks)
(a) What is a conformation? [2 marks]
(b) Use a newman projection, about the indicated bond, to draw the most stable conformer for each compound given below.
(i) Ethane (C1 – C2) [2 marks]
(ii) Butane (C2 – C3) [2 marks]
(iii) Propane (C1 - C2) [2 marks]
(c) Draw a chair conformation of cyclohexane and show both axial and equatorial C- H bonds. [3 marks]
(d) Briefly explain the following terms:
(i) Torsion angle [2 marks]
(ii) Torsion strain [2 marks]
(e) With help of newman projection structures, explain why chair conformation of cyclohexane is more stable than the boat conformation. [5 marks]
Question Three (20 Marks)
(a) When n - heptane burns in a gasoline engine, the combustion process takes place too quickly. The explosive detonation makes a noise called knocking. When 2, 2, 4- trimethyl pentane is burned, combustion takes place in a slower, more controlled manner, combustion is a free-radical chain reaction and its rate depends on the reactivity of the fuel-radical intermediates.
(i) Draw a structure of 2,2,4 – trimethyl pentane. [2 marks]
(ii) Explain why 2, 2, 4 – trimethyl pentane has less tendency to knock than does n - heptane. [3 marks]
(iii) Draw any three possible structural isomers of n – heptanes. [3 marks]
(b) Draw the structure of the following compounds
(i) 3 – bromo – 2 – methylpentane [2 marks]
(ii) (E) – 3 – methylhept – 3 – ene [2 marks]
(iii) (Z) – 3 – methylhept – 3 ene [2 marks]
(c) State Markornikov’s rule. [2 marks]
(d) Starting 1 – butanol, show how you would synthesize:
(i) 2 – Bromobutane [2 marks]
(ii) 1 – Bromobutane [2 marks]
Question Four (20 Marks)
(a) Predict the major products in each of the following reactions.
[O]
(i) CH3CH2 CH2
|
OH
KMnO4
(ii) CH3CH2C = C CH3
H2O, neutral [1 mark]
v
(b) Oxidative clearage can help to determine the position of the triple bond in alkaynes. An unknown alkyne undergoes oxidative cleavage to give propanoic acid and ethanoic acid.
(i) propose a structure for the unknown alkyne. [2 marks]
(ii) What are the conditions that will favour this oxidative cleavage? [2 marks]
(iii) Write a chemical equation showing this cleavage. [2 marks]
(c) The following compounds are only slightly soluble in water, but one of them is very soluble in a dilute aqueous solution of sodium hydroxide. The other is still only slightly soluble
OH OH
(ii) Explain the difference in solubility of these compounds in dilute sodium hydroxide. [3 marks]
(ii) Show how this difference might be exploited to separate a mixture of these two compounds using a separatory funnel. [3 marks]
(d) Determine the reaction type and predict the product(s) for each of the following vague reactions.
(i) CH3 CH2 – CH2 – I + NAOH [2 marks]
(ii) CH3 – CH2 – Br + 2CH3 – CH2 – CH2 – NH2 [2 marks]
Cr2? O?_7^(2-) [2 marks]
(iii) CH3 – CH – CH3 H2 SO4
|
OH
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