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Organic chemistry 1 and 2 research questions

UNIVERSITY OF NAIROBI

UNIVERSITY EXAMINATIONS 2011/2012

FIRST YEAR EXAMINATIONS FOR THE DEGREE OF BACHELOR OF SCIENCE

SCH 102: ORGANIC CHEMISTRY I

DATE:21ST MAY 2012 TIME: 9.00 TO 11.00

ANSWER ALL QUESTIONS
Q1 a) What do you understand by each of the following?
(i) Intermolecular forces [1 mark]
(ii) stereocentre [1 mark]
(iii) Hybridization [1 mark]

b) In a laboratory experiment to prepare methanol (CH3OH), a reaction vessel was filled with 35.4 g of carbon monoxide (CO), and 10.2 g of hydrogen (H2)
(i) Write a balanced equation for the reaction [1 marks]
(ii) Find the limiting reagent (show your calculation) [4 marks]
(iii) Calculate the theoretical yield of methanol [2 marks]

c) From the following data
Compound I Compound II
Melting point (° C) -57 101
Boiling point (° C) 126 106

Deduce which of the structures, A or B is compound I and which one is compound II. Give an explanation for your choice
[5 marks]

Q2 a) Sketch the conformational analysis graph for the compound 1-iodopropane (CH2ICH2CH3), rotated via C1-C2 bond through the angles of 0? to 180?.Label each minima or maxima with the correct Newman projection formula and name the conformation [8 marks]

b) Asign R or S configuration to all chiral carbons in each of the following compounds.[6 marks]
c) Draw the two possible chair conformations of cis-1-neopentyl-3-ethylcyclohexane. Compare the stabilities of the two conformers. [6 marks]

Q3 a) Give the structural formula for each of the following compounds
(i) 5-(1,1-dimethylethyl)-5-benzyldodecane
(ii) 1-Bromo-3-neopentylcyclopentane
(iii) 1-Ethyl-7-methylspiro[4,5]decane
[6 marks]

b) Write the IUPAC name for each of the following structures.[6 marks]
c) (i) Explain why the compound 2-chloropentane from the reaction below is found to be optically inactive.
[3 marks]
(ii) Draw the Fischer projection formula for all the stereoisomers of 2,3-dibromobutane (CH3CHBrCHBrCH3)with enantiomers opposite each other. Indicate the meso compound if any. [4 marks]

 

 

4 a) Write the complete mechanism for the following reaction using curly arrows to show movement of electrons
[8 marks]
b) Write the structural formula and IUPAC name for the product in the following reactions
[8 marks]

 

41456-chem-130-organic-chemistry-i

 

 

33062-sch-103-basic-organic-chemistry

 

 

48096-sch102-organic-chemistry

 

 

20366-chem-312-april-2011

 

 

60083-sch-202-organic-chemistry-ii

 

 

62522-chem-231-organic-chemistry-ii

 

Author

jaoganga@gmail.com