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(chem313)[2008](s)mid~PPSpider^_10047.pdf
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CHEMISTRY 313 INTERMEDIATE ORGANIC CHEMISTRY

Mid-Semester Examination

Friday April 11 2008 Room 2406 Time Allowed: 120 minutes
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Enter your name, and student ID number, on the beige answer booklet. Answer all questions. Read the questions carefully before answering. There is a total of 120 points for this examination paper.
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There are 3 pages of examination questions





Do not open this examination paper until instructed to do so.


1a. Consider the compounds 1a-1f OHOOCCOOHOHOHOHOHOHHOOCCOOHOHOHOHOHOHCH3SCH3HHOHHHOCH2CHOOHOHOHOHOCH3HHOCH31d1e1a1b1c:1f

i. Draw the Fischer projections for compounds 1a, 1b and 1c. (9 pts)

ii. What is the stereochemical relationship between 1a and 1b? (1 pt)

iii. Assign configuration at the chiral (chirogenic) centres as 'R' or 'S' in those compounds which contain such centres. (8 pts)


iv. Select one compound which contains a pseudoasymmetric centre and label the centre as 'r' or 's' (2 pts). v. Select one compound which contains homomorphic groups, and identify the groups. (2 pts). vi. Select one compound which contains enantiomorphic groups, and identify the groups. (2 pts) vii. Select one compound which contains a prochiral centre, and assign the attached ligands as 'pro-R' and 'pro-S' respectively. (4 pts) viii. Select one compound which contains diastereotopic ligands, and identify them. (2 pts) ix. Select one compound which contains hetereotopic faces. Identify these either as enantiotopic or diastereotopic, and label as 'Si ' or 'Re' as appropriate. (3 pts) x. Compound 1c is in equilibrium with two cyclic six-membered chair forms. Give the stereostructures of these cyclic forms, and label as '.' and '.' respectively. (5 pts) 1b. Consider compounds 1g and 1h. i. Given that the A values for the p-toluenesulfonate group (-OTs or -OSO2C6H4CH3-p) is 0.50 kcal mol-1 and the N,N-diethylamino group [CN(CH2CH3)2] is ~2.8 kcal mol-1, draw out the more stable chair conformer for each of the compounds 1g and 1h. (4 pts) ii. Indicate with careful reasoning which of compound 1g or 1h on heating in aqueous ethanol undergoes fragmentation more readily to give the the iminium salt 1i. (5 pts) iii. How do you think the iminium salt 1i may be converted into the aldehyde 1j (do not give mechanism). (2 pts). 1c. Indicate the reagent and conditions required to carry out the following transformation. Do not give mechanisms. (4 pts) 2a. Indicate with brief reasoning how the following transformation are carried out. You may use any other chemical or reagent as may be required.