Basic Concepts of Organic Chemistry (DSC-1, Chemistry-01) — DU B. Sc. Life Science (Chemistry) Previous Year Question Papers

1. Write the products) with complete chemical reaction for any five of the following. Name the reaction and the intermediate involved. (a) Benzene is treated with acetyl chloride in presence of AIC!, (b) Phenol is treated with chloroform in presence of sodium hydroxide, (c) Cyclohexanone oxime is treated with concentrated sulphuric acid, (d) Two moles of acetaldehyde are made to react in presence of NaOH. (e) Prop-2-enal is treated with diethyl malonate in presence of hydroxide ion. (f) 2,3-Dimethylbutane-2,3-diol is treated with dilute sulphuric acid (g) Propene is reacted with BH, followed by oxidation with H,O, in presence of NaOH. (3x5) 2. Give reasons for the following : (Any five) (a) Benzyl carbocation is more stable than allyl carbocation, (b) Acetaldehyde reacts faster than acetone towards nucleophilic addition reaction. (c) pk, of nitroacetic acid is 1.68 while pk, of acetic acid is 4.76. (d) Aniline is less basic than ethylamine. (e) 2,3-Dimethylbut-2-ene is more stable than but-2-ene, (DAryl halides have very low renctivity towards nucleophilic substitution reaction as compared to alkyl halides. (3×5) 3. (a) Assign E/Z or R/S to the following : (b) Draw the various conformations of n-butane and arrange them in increasing order of their stability. Give reasons for the stability order. (c) Why Sy' reactions are accompanied by racemization? (2x4,4,3) 4. (a) Distinguish between : (i) E, and E, reaction (ii) Racemic mixture and meso-Compound (b) Write the products) and mechanism involved when prop-l-ene reacts with HBr in i) presence and il) absence of peroxide. (c) Write products of the following reactions and state the type of the reaction involved: (i) Propyne is treated with dilute sulphuric acid in presence of mercuric sulphate. (i) 2-Chlorobutane is treated with aqueous sodium hydroxide. (5x3) 5. (a) Explain why halogens in haloarenes are weakly deactivating and ortho/para directing. (b) Explain the formation of different products formed when ethyl bromide is treated with NaCN and AgCN. (c) What happens when chlorobenzene is treated with NaNH, in liquid NH,? Give the mechanism involved. (5x3) 6. Write short notes (with mechanistic details) of any three of the following : (a) Perkin Reaction (d) Benzoin Condensation (5x3)