LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
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B.Sc. DEGREE EXAMINATION – CHEMISTRY
SIXTH SEMESTER – April 2009
CH 6609 / 6603- SYNTHETICS ORGANIC CHEMISTRY AND SPECTROSCOPY
Date & Time: 25/04/2009 / 9:00 – 12:00 Dept. No. Max. : 100 Marks
PART – A
Answer ALL questions: (10 x 2 = 20)
- What is retrosynthetic analysis in Organic chemistry.
- What is disconnection approach.
- Write the mechanism of C-alkylation of acetoacetic ester.
- Write the product of aldol condensation of Acetaldehyde.
- Predict the product of Diel’s – Alder reaction.
(i) (ii)
- Write the structure of the product
(i) (ii)
- Calculate the max value for the following compounds using Woodward Fieser rule?
(i) (ii)
- Concentrated solution of ethanol and 1, 2- glycol in CCl4 exhibit broad O-H stretch near 3350 cm-1 in their IR spectra. On dilution with CCl4 the spectrum of 1, 2 – glycol does not change but that of ethanol exhibits a sharp band at 3600 cm-1 in addition to the broad band at 3350 cm-1. Explain the observation.
- C13 is NMR active while C12 is not explain.
- How will you account for the appearance of prominent peaks at m/z 31, 42 and 70 in the mass spectrum of n- pentanol.
PART – B
Answer any EIGHT questions: (8 x 5 = 40)
- Explain Umpolung synthesis.
- What is the difference between conversion and synthesis.
- Predict the product of Birch reduction of
- Benzoic acid (ii) Anisole.
- Explain the product and mechanism of hydroboration of propene.
- Write the mechanism and stereochemistry of Diel’s Alder reaction of
- Discuss the method of protecting aldehyde and keto group?
- Explain the importance of molecular in peak in mass spectra.
- Write note on i) bathochromic shift ii) coupling constants
- How many different set of equivalent protons do each of the following compounds have? How many signals would each compound give in its lH NMR spectram
- CH3-CH3 ii) CH3-O-CH3 iii) CH3-CH2– -CH2-CH3 iv) CH3 – -O CH3
- Give a brief account on Refrence standards used in ‘H NMR spectral technique.
- The IR spectrum of methyl salicylate shows the following peaks at 3300 cm-1 1700 cm-1 3050 cm-1, 1540 cm-1, 1590 cm-1 and 2950 cm-1. Attribute these peaks to the following features of the molecule.
- What is meant by shielding and Deshielding of protons in NMR spectoscopy.
PART – C
Answer any FOUR questions: (4 x 10 = 40)
- What are the application of Electrophilic Synthon and Synthetic equivalent in Retro Synthetic analysis.
- i) How does IR spectroscopy useful to distinguish between a) O-nitro phenol and p-
nitrophenol.
- A compound having the molecular formula C10H14 exhibits following HlNMR signals. d28(5H singlet) 0.880 (9 H S). Assign the structural formula of the compound.
- i) How are the following groups protected and de protected during the synthesis of organic compound.
- –NH2 b) –OH group
- An organic compound A (molecular formula C9H10O2) exhibits the following spectral data
IR: 1745 cm-1, 1225 cm-1 749 cm-1 697 cm-1
UV: lmax 268, 264
|HNMR=d1.96(3H, S) 5.00(2H, S) 7.22(5H, S)
- i) How will you synthesis i) Acetylacetone ii) Crotonic acid from ethylacetoacetate.
- “Diels-Alder reaction is highly stereo specific”. Explain.
- Using Umpolung reaction how will you synthesis
- C6H5-CH2– -CH3 ii)
- Explain any two of the following (5+5)
- Clemmenson reduction and its mechanism
- Working principle of UV=Visible spectrophotometer with a block diagram.
- Oxidation by peracids.