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(solution) Can I get all answers with full solutions please. Thank you


Can I get all answers with full solutions please. Thank you  


DUBLIN CITY UNIVERSITY

 

SEMESTER 1 EXAMINATION 201 1

 

Analytical Science

 

Chemical & Pharmaceutical Sciences

 

Environmental Science & Health

 

Genetics & Cell Biology

 

Science Education (Ycar 3)

 

SHSAX MODULE: CS204

 

Organic Chemistry

 

)ATE: January 20 11 TIME:

 

EXAMINERS: Dr. P. James

 

Dr. P. O'Malley DIJRATION: 2 Hours INSTRUCTIONS: Answer THREE questio~is. 5126

 

5312 'THE USE OF PROGRAMMABLE OR TEXT STORING CALCULATORS IS

 

EXPRESSLY FORBIDDEN.

 

PLEASE NOTE THAT WHERE A CANDIDATE ANSWERS MORE THAN

 

T1111: REQUIRED NUMBER OF QUESTIONS, THE EXAMINER WILL

 

MARK A1,L QUESTIONS ATTEMPTED AND THEN SELECT THE

 

HI(; HEST SCORING ONES. DO NOT TURN OVER THIS PAGE UNTIL YOU ARE TOLD TO DO SO - This booklet contuin.~

 

.five pages including the cover,shc.e/

 

Page l ol' S / CS204 Semester l Answer THREE questions. 1. Answer ALL parts. [Marks: (a) 60% (b) 40%]

 

(a) Propose a reasonable synthesis of each of the following disubstituted

 

aromatics from benzene: I COOH (1)) Strongly electron withdrawing substituents on benzene rings are w z e i ~ ~

 

directing. Show by drawing the resonance structirres for the various

 

possible intermediates why this is the case using nitrobenzenc as an

 

example. Page 2 of 5 1 CS204 Semester 1 2. Answer A1,L parts. [Marks: (a) 50% (b) 50% ] (a) For each of the following molecules, drawn as Fischer projections, assign Ihe

 

absolute stereochemistry (R or 5') at the chiral centre (or centres). Show your

 

reasoning.

 

COOH H

 

CH20H (b) CH,OH CH3 CI 'I'hc structure of me,s.o-butane-2,3-diol is shown. (i) Redraw the structure and assign R or S to each of the chiral ccntres in

 

rtze.so-butane-2,3-diol. (ii) Draw a Fischer projection of meso-butane-2,3-diol. (Note: 11 should

 

have a plane of symmetry) Page 3 of 5 1 CS204 Semester I 3. Answer ALL parts. [Marks: (a) 40% (b) 60% ]

 

(a) ( i ) Show the Mechanism for the following base catalysed double

 

Aldol condensation reaction, illustrating how the major dehydration

 

product is formed: (iii) Show the Mechanism for the following two step Malonic Estcr

 

synthesis, showing the products formed: (h) For each of the following reactions, name the 'reaction type' and show

 

the product(s) formed : (ii) Page 4 of 5 I CS204 Semester 1 3. ( b ) cont'd

 

(v) 4. Answer ALL parts. [Marks: (a) 40% ; (b) 60% ]

 

(a) ( i ) Name the following compounds (ii) I)~;Lw both chair conformations for cis-1-tert-butyl-2-methylcyclohcxa~~e. atid explain which is the more stable conformer. (b) Complete reactions I and 1 , indicating which reaction proceeds by an

 

1

 

SN1 mechanism and which reaction proceeds by an SN2mechanism.

 

I CH3Br + -OH - Itcferring to reactions 1 and 11, write notes comparing the SN1mccha~~ism

 

and SN2mechanisn~i n terms of suhslrule, nucleophile, /euvirzg ~ V ~ L I J I ,

 

1.c11e I t r i d , and ~tereochemi~stry. Ilraw the energy profile diagram for each of the above reactions, I and 11. Page 5 of 5 1 CS204 Semester I

 


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