SIKKIM UNIVERSITYDepartment of Chemical Sciences

CHE-RS-E108: Strategies in Organic SynthesisUnit-1, September 9, 2015

Dr. B. G. Roy

Total Marks: 50 Time: 2 hSection A

Answer any Five (5 x 1 = 5)

1. Relation between two following molecule isa. Enantiomerb. Diastereomerc. Homomerd. Constitutional isomer

2. What type of chirality does this molecule poses?a. Achiralb. Planner Chirality c. Axial Chirality d. Helical chirality

3. The major product formed in the following reaction is

4. The major product of the following reaction is

5. Stereoisomers I and II undergo E2 elimination on treatment with sodium ethoxide in ethanol.One isomer reacts 500 times faster than the other. Also, one isomer gives X as the only product,

a) II reacts faster and gives both Y & X

b) II reacts faster and gives only Xc) I reacts faster and gives both Y & X

whereas the other gives Y together with some X. Which of the following statements provides the best assignment of I and II?

Section B

Answer any Three (3 x 15 = 45)

2. a) Write major product of the following reaction. 2

b) For preparation of product which reaction you will choose and why? 3

c) Write correct product with proper stereochemistry 2

d) Write the major products of following reaction with proper stereochemistry.

2 x 4 = 8

iii)

b) What will be products of following reactions? Write Proper mechanism in each case. 10

a) II reacts faster and gives both Y & X

b) II reacts faster and gives only Xc) I reacts faster and gives both Y & X

i) ii)

2. a) Write missing reagents and products. Give mechanism in each case. 3+3 = 6

i.

ii.

b) How will you synthesize these following compounds? 3

c) Give reagents for each of these of the following transformation. The reaction rate is 104 times faster than methylacrylate and gives very high regioselectivity. Give reason for that. 3

d) Write mechanism for following transformations. 3

3. a) Write stereochemical structure of major products. 6

i) ii)

iii)

b) Write stereochemical structure of major products. 3

c) Write stereochemical structure of major products. 4

c) How will you carry out following transformations? Give proper reagents and mechanism. 2

4. a) Write major product with proper stereochemistry. 3

b) Write major product with proper stereochemistry. 2

c) Write major product with proper stereochemistry. 3

b) Write stereo chemical structure of major products. 4

,

c) Write stereochemical structure of major products. 3

Thank You