JUNE – 2021
B. Sc. (VI Semester) Examination
CHEMISTRY
Paper: CHEM-363
(Organic Chemistry)
Full Marks : 80
Pass Marks : 35%
Time : Three Hours
Note: (i) Answer all the questions.
(ii) The figures in the margin indicate full marks for the questions.
1. Answer all the questions: 2x5= 10
(a) Explain why malonic ester is preferred over acetoacetic ester in the synthesis of carboxylic acids.
(b) What is chromogen? Give two examples.
(c) Why are amino acids amphoteric in nature?
(d) Given an example of [5,1] sigmatropic rearrangement.
(e) Define quantum yield.
2. Answer any four questions: 5x4= 20
(a) Outline the synthesis of 3-ethylpentan-2-one from ethyl acetoacetate. 5
(b) Write the synthetic route of Indigo. 5
(c) Discuss the Strecker synthesis of leucine. 5
(d) (i) What is meant by Antrafacial overlapping? 1
(ii) Explain frontier orbital method for (4+2) cycloaddition of 1, 3-butadiene and ethane. 4
(e) (i) Explain Norrish type-II reaction with suitable example. 3
(ii) Complete the following reaction 2
3. Answer any five questions. 10x5 = 50
(a) Starting from acetic acid, how will you prepare DEM. Outline the synthesis of following compounds from malonic ester. 4+3+3= 10
(i) Isobutyric acid
(ii) Cinnamic acid
(b) (i) Give the preparation of methylorange. How it acts as indicator in acid-base titration. 3+3= 6
(ii) Explain the colour change of phenolphthalein in alkaline medium giving chemical reaction. 4
(c) (i) Give a method for the synthesis of peptide bond by taking leucine and alanine. 6
(iii) Discuss the secondary structure of protein. 4
(d) (i) Write the selection rule for electrocyclic reactions. Predict the product of the following reactions. 5
(e) Describe photo physical processes in electronically excided molecules. 5
(f) Write short notes on the following (any two) 5x2= 10
(i) Cope rearrangement
(ii) Diels-Alder reaction
(iii) Photo reduction of benzophenone
