PHARMACEUTICAL CHEMISTRY-II (ORGANIC-I) THEORY Question Papers 4 A.U

Answer question no.1(compulsory) and any four of the remaining. All questions carry equal marks

1. a) Give reasons for the following:

• Ethlyl alcohol gives iodoform reaction whereas n-propyl alcohol does not.
• Dry solvents must be used for the preparation of Grignard's reagents.
• Although HCl is a longer molecule than HF, it has a smaller dipole moment.
• n-Butyl alcohol has a much higher boiling point than its isomer diethyl ether, yet both compounds show the same solubility in water. (4*2=8).

b) Explain geometrical isomerism in detail giving suitable examples.

2. a) Explain SN 1 and SN 2 reactions. Compare and contrast them. b) Explain the method of preparation and mention the uses of i) Iodoform (ii) Diethyl ether.

3. a) Write the structures of the following compounds:

• 3-chloro-2,4-dimethylhexane.
• tert-butyl benzyl ether.
• propylene glycol
• 3-chloro-2-methylpentanol
• (z)-3-chloro-4-methyl-3-hexane
• 4-methyl-2-pentyne
• cis-1,2 dimethyl cyclopropane
• tert-butyl ethyl ether.

b) Explain conformational isomerism giving suitable examples. Discuss the stability of conformational isomer. Discuss the phenomena in cycloalkanes also.

4. (a) Write about the industrial sources of alcohols. (b) Write two methods for the preparation of alcohols. (c) Write about the reaction of alcohols with hydrogen halides. What is the mechanism of this reaction? What is the order of reactivity of alcohols towards hydrogen halides?

5. (a) What is meant by the following?

• Optical activity
• Chirality
• Configuration
• Confirmation

(b) Draw and specify as R and S the enantiomers of (i) Sec-Butyl chloride (ii) Alanine.
(c) Draw stereochemical formulas for all the possible stereoisomers of the following compounds. Label pairs of enantiomers, diastereomers and meso compounds (i) 1,2-dibromopropane (ii) Z-bromo-3-chlorobutane.

6. (a) Write the mechanism of the following reactions:

• Dehydration of alcohols.
• Chlorination of methane
• Hydration of alkenes

(b) Write the reaction of Grignard's reagent with

• Formaldehyde
• Benzaldehyde
• Acetone
• Ethylacetate.

7. (a) Write the reaction of :

• Reduction of 2-butyne
• Hydration of acetylene
• Hydration of 2-butyne

(b) Write the products of ozonolysis of

• Propylene
• 1-butyne
• 2-butene

(c) Write the mechanism of Williamson synthesis.

8. Write short notes on the following:

• Bayer's strain theory
• Stability of conjugated dienes
• Homolysis and heterolysis
• Intra and inter molecular forces.