LOYOLA COLLEGE (AUTONOMOUS) CHENNAI – 600 034
B.Sc., DEGREE EXAMINATION – CHEMISTRY
SIXTH SEMESTER – APRIL 2011
CH 6609/6603 – SYTHETICS ORGANIC CHEMISTRY AND SPECTROSCOPY
DATE:11-04-2011 MAX:100 MARKS
TIME:1:00 – 4.00
Answer ALL Questions (10 x 2 = 20)
- What are activating groups? Give
- Suggest any two criteria for choosing protective groups?
- Complete the following reactions
Pd / C
- Mention the role of DMSO in oxidation reactions
- What is the structure of aldol product from propanal?
- What is the significance of active methylene group?
- Calculate the lmax for the following
- C – CH3
- The lmax of benzene is 256nm whereas aniline is 280nm – Give reason.
- Predict the structural formula for the compound with the following molecular formula showing only one NMR signal a) C2H6O b) C5H12
- Define nitrogen rule. Give an example.
Answer any EIGHT Questions (8 x 5 = 40)
- Explain Retrosynthetic analysis.
- What do you understand by linear and convergent synthesis? Explain.
- Discuss synthon approach in construction reactions.
- Discuss the mechanism of Clemmenson reduction and mention its significance.
- Explain hydroboration reaction and mention the utility of the rection.
- Explain Diels Alder reaction. Give any two examples.
- Complete the following reaction
+ C6H5CHO NaOH
- CH3 – (CH2)7 – CH = CH2
- What are chromophores and auxochrome? Give examples.
- Discuss the factors which affect the IR absorption frequency of a functional group.
- Define chemical shift. Why is TMS a good reference standard in NMR spectroscopy.
- How will you distinguish 2-pentanone and 3-pentanone using mass spectroscopy.
- Explain shielding and deshielding mechanism.
Answer any FOUR Questions (4 x 10 = 40)
- a) Explain umpolung synthesis. (5)
- b) Using umpolung synthesis convert the following reaction. (5)
nC5H11 – C – H C5H11 – C – CH2 – R
- a) How will you distinguish the following pairs using IR spectroscopy. (6)
- CH3 – CO – CH3 and CH3 – CH = CH – CH2OH
- O-hydroxy benzaldehyde and m- hydroxy benzaldehyde
- b) Draw the structure of each of the following compounds which meets the given requirements in the NMR spectrum. (4)
- C3H3Cl5 (one doublet and one triplet) ii. C3H7Cl (one doublet and one septet)
- a) Explain spin-spin spliting with a suitable example. (6)
- b) A compound with molecular formula C8H8O gives the following NMR spectrum – multiplet
d28 (5H), Doublet d 2.88 (2H), Triplet d 9.87 (1H). Determine its structure (4)
- Using malonic ester how will you synthesis the following.
- Succinic acid Adipic acid
- Cinnamaldehyde n-Valeric acid.
- Barbituric acid.
- a) An organic compound with molecular weight 72 absorbs at 274 nm.
In IR the bands are formed at 1715 cm-1 (s), 2941 – 2857 cm-1(m) and 1460 cm-1 (m).
In NMR the signals formed are 2.48 d quartet (2H), 2.12 d singlet (3H), 1.07 d triplet (3H). Determine the structure of the compound.
b)Define the following terms and mention its significance (4)
- Base Peak ii. Metastable peak
- a) Discuss the instrumentation of UV –Visible spectrophotometer with the block diagram.(6)
- b) How are the following groups protected and deprotected during organic synthesis (4) – NH2 ii. C = O iii. – OH iv. – COOH