SECTION-I (SINGLE CORRECT CHOICE)

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1 SECTI-I (SIGLE CRRECT CICE) 1. Which of the following phrases are not correctly associated with an S1 reaction? 1. Rearrangement is possible. 2. Rate is affected by solvent polarity. 3. The strength of the nucleophile is important in determining the rate. 4. The reactivity series is tertiary > secondary > primary. 5. Proceeds with complete inversion of configuration. (A) 3, 5 (B) 5 only (D) 2, 3, 5 (D) 3 only 2. Select the reagent that will yield the greater amount of substitution on reaction with 1-bromobutane. (A) C3C2K in dimethyl sulfoxide (DMS) (B) (C3)3CK in dimethyl sulfoxide (DMS) (C) Both (A) and (B) will give comparable amounts of substitution. (D) either (A) nor (B) will give any appreciable amount of substitution 3. In the S2 reaction of iodide ion with (C3)2CC2C2X what is the order of decreasing reactivity for the following X substituents? I X = - II X = C3C2 - III X = CF3S3 - IV X = C3C2 - (A) I > II > III > IV (B) IV > III > II > I (C) III > II > IV > I (D) III > IV > II > I 4. If the rate of reaction of 0.1 M sodium cyanide with 0.1M 1-bromoethane is 1.4 x 10-4, what effect will an increase in ac concentration to [0.3] and alkyl bromide concentration to [0.2] have on the overall reaction rate? (A) increase by 2 times (B) increase by 3 times (C) increase by 6 times (D) increase by 1.5 times 5. Which of the following statements is true? (A) C3C2S - is both a stronger base and more nucleophilic than C3C2 -. (B) C3C2S - is a stronger base but is less nucleophilic than C3C2 -. (C) C3C2S - is a weaker base but is more nucleophilic than C3C2 -. (D) C3C2S - is both a weaker base and less nucleophilic than C3C Which of the following statements pertaining to an S2 reaction are true? 1. The rate of reaction is independent of the concentration of the nucleophile. 2. The nucleophile attacks carbon on the side of the molecule opposite the group being displaced. 3. The reaction proceeds with simultaneous bond formation and bond rupture. 4. Partial racemization of an optically active substrate results. (A) 1, 4 (B) 2, 3 (C) 1, 2, 3 (D) 2, 3, 4 7. ptically pure (S)-2-butanol is treated first with Ts and then with asc3. The product has a specific 0 rotation 25. If the same optically pure (S)-2-butanol is treated first with P3 and then with D asc3, the optical rotation of the product would be (A) 25 0 (B) (C) 0 (D) C 3 I C 3 a C 3 C C 3 I C 3 Ca C 3 Which of the following statements is true regarding the above two reactions? (A) Dimethyl ether and methyl acetate are the major products in the two reactions respectively. (B) thyl acetate and dimethyl ether are the major products in the two reactions respectively. (C) Dimethyl ether is the major product in both the reactions. (D) thyl acetate is the major product in both the reactions CEMISTRYWRLD.I Page 1

2 9. In an experiment, ughes studied the rate of racemisation of 2-iodooctane by sodium iodide (with radioactive iodine) in acetone and compared it with the rate of incorporation of radioactive iodine into 2- iodooctane. * acetone * * RI I RI I (I is radioactive iodine) ow will the rate of racemisation compare with the rate of incorporation if (I) Each act of exchange proceeds with retention (P) 2 rate of racemisation = 2rate of incorporation of configuration (II) Each act of exchange proceeds with (Q) rate of racemisation = rate of incorporation inversion of configuration (III) Each act of exchange proceeds randomly in (R) no inversion which retention and inversion are equally likely. (A) I-P, II-Q, III-R (B) I-R, II-P, III-Q (C) I-P, II-R, III-Q (D) I-R, II-Q, III-P 10. Which of the following isomeric chlorides will undergo S2 substitution most readily? A) 4-chloro-1-butene B) 1-chloro-1-butene (cis or trans) C) 1-chloro-2-butene (cis or trans) D) 2-chloro-1-butene 11. A C713 compound reacts with K in ethanol to form 3-methylcyclohexene as the major product. What is a likely structure for the starting alkyl bromide? A) cis-4-methylcyclohexyl bromide B) trans-3-methylcyclohexyl bromide C) cis-2-methylcyclohexyl bromide D) trans-2-methylcyclohexyl bromide 12. All of the following alkyl bromides react by S2 substitution when treated with sodium cyanide in methanol. Which one does not undergo an inversion of configuration? A) (R)-1-bromo-2-methylbutane B) (S)-2-bromo-3-methylbutane C) (R)-1-bromo-3,3-dimethylcyclohexane D) cis-4-ethyl-1-bromocyclohexane 13. Consider the S1 solvolysis of the following 1 -alkyl chlorides in aqueous ethanol. I C3C2C2 II C2=CC2 III C3C2 IV CF3CF2C2 What is the order of decreasing reactivity? A) III > II > I > IV B) II > III > I > IV C) IV > III > II > I D) I > II > III > IV 14. The structures of two 3 -bicyclic chlorides (I and II) are shown below. Which of the following statements is correct? A) on treatment with K in ethanol, both compounds undergo E2 elimination. B) on treatment with K in ethanol, I undergoes substitution and II undergoes elimination. C) I is more reactive than II for both substitution and elimination D) II is more reactive than I for both substitution and elimination 15. Which of the following reaction sequences would best serve to convert 2-methyl-1-bromopropane to 4- methyl-1-iodopentane? A) (i) Mg in ether;.(ii) ethylene oxide (C24); (iii) I & heat B) (i) ac C in ether;.(ii) 2 + Lindlar catalyst; (iii) I C) (i) K in alcohol;. (ii) C65C3 in C22; (iii) ac C in ether ; (iv) Pt catalyst D) (i) ac C in ether;.(ii) gs4; (iii) I & heat CEMISTRYWRLD.I Page 2

3 16. A C814 hydrocarbon (X) is reduced by sodium in liquid ammonia to a single C816 product (Y). Both of these compounds undergo hydrogenation (Pt catalyst) to give 2,5-dimethylhexane. zonolysis of Y with an oxidative workup produces a single C482 carboxylic acid. Reaction of Y with perbenzoic acid (C65C3) gives a chiral C814 product, but reaction with bromine gives an achiral C8142 product. What are X and Y? A) X is 2,5-dimethyl-3-hexyne ; Y is cis-2,5-dimethyl-3-hexene. B) X is 2,5-dimethyl-3-hexyne ; Y is trans-2,5-dimethyl-3-hexene. C) X is 2.5-dimethyl-1,5-hexadiene ; Y is 2,5-dimethyl-3-hexyne. D) X is 2,5-dimethyl-2,4-hexadiene ; Y is cis-2,5-dimethyl-3-hexene. 17. Compound X reacts with I. The product of this reaction, when treated with K in ethanol, gives Y (an isomer of X). zonolysis of Y (22 workup) produces two compounds: a two carbon carboxylic acid, and a four carbon ketone. What is X? A) 2-methyl-2-pentene B) 4-methyl-1-pentene C) 2,3-dimethyl-2-butene D) 3-methyl-1-pentene 18. Azide anion is a very good nucleophile. Predict the major product from the following reaction. 19. Solvent Dielectric constants( ) thanol Ethanol 42.7 C C C3C2C2 + a3 Above reaction is fastest in (A) thanol (B) 2 (C) C3C (D) Ethanol 20. CC 3 A student tried to bring about the above conversion in the following two methods. I) i. K ii. C3C II) i. Ts/py ii. C3Ca Select the correct statement. (A) I gives a better yield of the product. (B)II gives a better yield of the product. (C) ne is as good as the other. (D) one of them gives satisfactory yield. 21. The reaction of (R)-1-chloro-3-methylpentane with sodium iodide in acetone will yield 1-iodo-3- methylpentane that is (A) R (B) S (C) A mixture of R and S (D) so 22. Which of the following reacts faster in an S1 reaction? I. cis-4-tert-butylcyclohexyl bromide II. trans-4-tert-butylcyclohexyl bromide (A) I (B) II (C) both at equal rate (D) both of them do not undergo S1 reaction CEMISTRYWRLD.I Page 3

4 23. Devise a series of reactions to convert benzene into meta-chlorobromobenzene. Select reagents and conditions from the following table, listing them in the order of use. 1 sulfuric acid (conc.)/ heat Fe3 & heat 6 P3 7 3P2 8 3 (conc.) + 2S4 (conc.) & heat 3 a2 + 3 (+) /0 ºC 4 2/Pt catalyst 5 Mg in ether 9 Cu (C3C)2 + pyridine (A) 1 then 2 then 6 (B) 2 then 8 then 4 then 3 then 9 (C) 8 then 4 then 10 then 2 then 3 then 9 (D) 8 then 2 then 4 then 3 then Stereoisomers I and II undergo E2 elimination on treatment with sodium ethoxide in ethanol. ne isomer reacts 500 times faster than the other. Also, one isomer gives X as the only product, whereas the other gives Y together with some X. Which of the following statements provides the best assignment of I and II? (A) II reacts faster and gives both Y & X (C) I reacts faster and gives both Y & X (B) II reacts faster and gives only X (D) I reacts faster and gives only X 25. (A) C B+C (isomers having m.f.c ) /peroxide D+E (isomers having m.f.c911) Cold alk KMn A 4 racemic mixture A is C=C-C 3 Which of the following is true about A? (A) A is cis isomer (C) Data insufficient to decide (B) A is trans isomer (D) one 26. Arrange the following species in the decreasing order of leaving tendency. 2 II. - - III. IV. - - I. RS2-2 2 (A) I > II > III > IV (B) III > II > I > IV (C) I > III > II > IV (D) III > I.> II > IV 27. A solution of pure (S)-2-iodobutane ( = ) in water is allowed to react with radioactive iodide, 131 I -, until 1% of the iodobutane contains radioactive iodine. If the reaction proceeds with S1 and there is complete racemisation, what is the specific rotation of the recovered reaction mixture? (A) (B) (C) 0 (D) 15 2 CEMISTRYWRLD.I Page 4

5 28. C 3 CEt + C - DMS S 2 Choose the correct statement (A) the product has S configuration (C) the product is optically inactive (B) the product has R configuration (D) one 29. A C614 chiral alcohol is converted to a bromide by treatment with P3. Reaction of this bromide, first with Mg in ether, followed by quenching in 0.1 produces an achiral C614 hydrocarbon. Which of the following is the original alcohol? (A) 2-ethyl-1-butanol (B) 4-methyl1-1-pentanol (C) 3-methyl-3-pentanol (D) 3-methyl-1-pentanol 30. C 2 2 S 4 2 Al 3 What is the major product of the above sequence of reactions? (A) (B) C 3 (C) C 3 (D) 31. Reaction of 1,1-dibromopentane with three equivalents of a2 in ether is followed by treatment with 0.1M at 0 C. What is the product? (A) cyclopentene. (B) 1,2-pentadiene. (C) 2-pentyne. (D) 1-pentyne. 32. Which of the following reagents and conditions would best serve to convert 1-butyne to 1,1- dibromobutane? (A) 2 equivalents of, no peroxides. (B) 2 equivalents of, with peroxides. (C) 1 equivalent of 2. (D) 2 equivalents of 2 followed by i equivalent of K. 33. Chloroethane, C25, does not react with methanol under mild conditions. What reagent could be added to the reaction mixture to increase the rate of substitution? (A) (conc.) (B) a (C) 4 (D) Ag3 34. Which of the following three compounds undergoes the fastest AS (ArS) reaction with hydroxide ion? I II III A) I B) II C) III D) I & II with equal ease CEMISTRYWRLD.I Page 5

6 35. + A umber of dichloro isomers (including stetreoisomers) formed, when A is treated with 2/hv, is (A) 6 (B) 8 (C) 10 (D) Which of the following compounds undergoes ArS reaction fastest? F F C 2 2 C 37. The final product of the following sequence of reactions is F eq Mg dry ether 2 (A) (B) (C) F (D) The major product of the following reaction is 1 eq. a (A) (B) (C) (D) + CEMISTRYWRLD.I Page 6

7 39. Which of the following undergoes ArS reaction most readily? (A) (B) (D) (C) (I) I a ai (II) I I (III) (C ) S (C ) S In which of the above S2 reactions, rate of the reaction increases on increasing the polarity of the solvent? (A) I (B) II (C) III (D) I & II 41. Ag 3 2 The major product of the above reaction is (A) (B) 42. If, in a S2 reaction, water acts as solvent as well as nucleophile, the reaction order can be expected to be (A) 1 (B) 2 (C) 3 (D) In ethanol/2 mixture, isopropyl bromide reacts with hydroxide ion according to the following equation 5 5 rate RX RX What percentage of isopropyl bromide reacts by S2 mechanism when = 0.1M? (A) 90% (B) 66% (C) 98% (D) 46% (C) (D) 44. ac 3 C 3 C 3 / Major product of the above reaction is CEMISTRYWRLD.I Page 7

8 C (C ) C a C C ex.a A B C liq C is Pyridine Major product of the above reaction is py h umber of monochlorinated isomers (including stereoisomers) formed in the above reaction is (A) 4 (B) 6 (C) 3 (D) K 2 C 3 Major product of the above reaction is C 3 C 3 C 3 C 3 CEMISTRYWRLD.I Page 8

9 49. K 2 3 Major product of the above reaction is The major product of the following reaction is C 3 C 2 5 a + Ph DMS 3 C C 2 5 C 2 5 C 3 C 2 5 C 3 C 2 5 C 3 Ph Ph Ph Ph 51. Reaction of 1,4-dibromobutane with Mg turnings in ether gives the bis-grignard reagent, MgC2C2C2C2Mg. What is the product from the reaction of meso-2,3-dibromobutane with Mg under the same conditions? (A) trans-2-butene (B) cis-2-butene (C) meso-c3c(mg)c(mg)c3 (D) racemic-c3c(mg)c(mg)c3 52. What is the order of reactivity of the following compounds in S2 reaction? (I) C3C2C2 (II) C2=C-C2 (III) C3CC2 (A) I > II > III (B) II > I > III (C) III > II > I (D) II > III > I C 4 a mixture containing A and B The relation between A and B is CEMISTRYWRLD.I Page 9

10 (A) Enantiomers (B) Diastereomers (C) Constitutional isomers (D) one of the above. 54. Select the best combination of reagents for the following conversion propane 2,2-dichloropropane (A) i. ex. 2/hv ii. Et/K iii. 2/C4 iv. 3 moles of a2 followed by + v. 2 moles of (B) i. 2/hv and large excess of propane ii. Et/K iii. 2/C4 iv. 3 moles of a2 followed by + v. 2 moles of (C) i) i. 2/hv and excess of propane ii. R/ K iii. 2/C4 iv. R/K K v. 2 moles of (D) i. 2 moles of 2 in the presence of light iv. 3 moles of a2 followed by + v. 2 moles of 55. * Mg dry ether C 3 C Mixture ow many isomers does the mixture contain? (C * is C 14 ) (A) 6 (B) 3 (C) 4 (D) 5 SECTI-II (Multi Correct) 56. Under the specified conditions, a substrate X undergoes substitution (with 2) and elimination reactions to give products A, B, C and D. A and B are stereoisomers but not enantiomers. C and D are enantiomers. A and C are not isomers. Which of the following could be the starting material X? (A) (B) C 3 (C) 3 C (D) C 3 C 3 C 3 3 C 3 C /hν (S)-2-Chlorobutane monochlorination The product which is/are formed in the above reaction is (A) (2S,3S)-2,3-dichlorobutane ( B) (2R,3R)-2,3-dichlorobutane (C) (S)-1,2-dichlorobutane (D) (R)-1,2-dichlorobutane 58. C 2 C 3 The products obtained in the above reaction is/are (A) (B) C 3 (C) C 2 C 3 C 3 3 C C 3 (D) + C 3 C 3 CEMISTRYWRLD.I Page 10

11 59. In which of the following options, all of which are S2 reactions, the first reaction is faster than the second? C (A) I. C3C2C 2I II. C3C2C2I DMS DMS I (B) I.C 3C2C2Ts II. C3C2C2 Ts DMS DMS 3 P (C) I. C C C Ts II. C C C Ts C C (D) I. C3C2C2 S2C3 II. C3C DMS 2C2S2CF3 DMS 60. Which of the following is/are polar aprotic solvents? (A) C3C (B) (C3)3 (C) C3CC3 (D) DMS 61. Under conditions of photochemical chlorination, (C3)3CC2C(C3)3 gives a mixture of two monochlorides. Select the correct statement(s) regarding the products. (A) The major product is more reactive than the minor product toward S1 solvolysis. (B) The major product is less reactive than the minor product toward S1 solvolysis. (C) S1 hydrolysis of the minor product gives 2,3,4,4-tetramethyl-2-pentanol as the major product. (D) Major product is optically active. 62. Which of the following give(s) white precipitate with aqueous Ag3? 63. C 3 -C=C-C 2 ac DMS The products formed in the above reaction is/are (A) C3C=CC2C (B) C2=C-C=C2 (C) C3-C(C)-C=C2 (D) C3-C=C(C)-C3 64. B 2 2 (R) A Select the correct statements regarding A and B. (A) A is a mixture of diastereomers (B) B is a mixture of enantiomers (C) A is a mixture of enantiomers (D) B is optically p 65. B C 3 a statement(s) 3 C Pyridine S 3 C C C 2 5 K C 3 I A correct Select the (A) A and B are enantiomers (C) B is (S)-2-methoxybutane (B) A is (R)-2-methoxybutane (D) A and B are diastereomers. CEMISTRYWRLD.I Page 11

12 SECTI-III Passage-I The ratio of elimination to substitution is exactly the same (26% elimination) for 2-bromo-2-methylbutane and 2-iodo-2-methylbutane in 80% ethanol + 20% water at 25 0 C. 66. By what mechanism does substitution most likely to occur in these compounds under these conditions? (A) S1 (B) S2 (C)Si (D) one 67. By what mechanism does elimination most likely to occur in these compounds under these conditions? (A) E1 (B) E2 (C) E1CB (D) one 68. Which of the following best explains as to why the ratio of elimination to substitution is exactly the same in these compounds? (A) 80% ethanol + 20% water at 25 0 C always gives the same ratio. (B) The ratio is same because of the formation of same carbocation. (C) omides and iodides always give the same ratio. (D) one Passage-II An alkane (A) with the formula C614 reacts with chlorine to yield three compounds (excluding stereoisomers) with the formula C613: B, C, and D. f these, only C and D undergo dehydrohalogenation with sodium ethoxide in ethanol to produce an alkene. Moreover, C and D yield same alkene E (C612). C is optically active. ydrogenation of E produces A. Treating E with produces a compound (F) that is an isomer of B, C, and D. Treating F with Zn and acetic acid gives a compound (G) that is isomeric with A. 69. C is (A) (B) (C) (D) 70. Correct statement regarding E is (A) It is the least stable alkene possible for the molecular formula C612. (B) It is the most stable alkene possible for the molecular formula C612. (C) It has two degree of unsaturation. (D) one of the above. Passage-III In the laboratories of the firm ovartis has been found a compound labelled achiral alkyl halide C1017. The management feels that the compound might be useful as a pesticide, but they need to know its structure. You have been called in as a consultant at a handsome fee. Compound A, when treated with K in ethanol, yields two compounds B and C, each with molecular formula C1016. Compound A rapidly reacts in aqueous ethanol to give an acidic solution. zonolysis of A followed by treatment with (C3)2S gives (C3)2C= as one of the products plus an unidentified halogen containing compound. ydrogenation of either B or C gives a mixture of both trans and cis 1-isopropyl-4-methylcyclohexane. A reacts with one equivalent of 2 to give a mixture of two separable compounds D and E, both of which can be shown to be achiral. Finally, ozonolysis of B gives (C3)2C= and the following diketone. CEMISTRYWRLD.I Page 12

13 71. D and E are (A) positional isomers (C) functional isomers (B) diastereomers (D) one 72. B is 73. Compound A, when reacts with ethanol, gives which of the following as the major organic compound? Et Et Et Et C 3 Passage- IV There are 5 isomers; A, B, C, D, & E with m.f. C77 of which A, B, C, & D are aromatic. E is quite soluble in water. When treated with Mg/dry ether followed by 2, A, B, C, and D give same compound F. But when treated with Mg/dry ether followed by D2, A, B, C, and D give four different compounds; G,, I, & J respectively. A and E readily react with aq. a. B, C, & D do not react with aq.a under normal conditions. 74. F is: (A) toluene (B) cycloheptatriene (C) benzene (D) none 75. E can be converted into an aromatic ion by treatment with I. Ag3 II. Al3 III. C3Mg IV. K (A) II & IV (B) I & II (C) II & III (D) I & IV Passage-V There are three isomers, A,B and C having the m.f. C38. Their boiling points are; A: C, B: C and C: C. There is another compound, D, whose molecular weight is same as that of above compounds but its m.f. is C242. The boiling point of D is C. 76. Treating A with P3 gives (A) n-propyl chloride (C) ethyl chloride 77. A and B are (A) Functional isomers (C) Diastereomers (B) isopropyl chloride (D) methyl chloride (B) Enantiomers (D) one 78. Treating D first with moist Ag2 and 2 followed by heating gives which of the following as major product (A) C3 (B) C3C2 (C) C4 (D) C26 CEMISTRYWRLD.I Page 13

14 Passage-VI Two compounds A and B have the molecular formula C1010. Both absorb four mol of 2 in the presence of i and give the following compound. Both A and B give phthalic acid with hot KMn4. A gives three monobromo isomers (excluding stereoisomers) with BS/C4. B gives two monobromo isomers (excluding stereoisomers) with BS/C Including stereoisomers, how many isomers does A give with BS/C4? (A) 6 (B) 4 (C) 5 (D) Including stereoisomers, how many isomers does B give with BS/C4? (A) 6 (B) 4 (C) 3 (D) 5 ASWERS 1 A 2 A 3 D 4 C 5 C 6 B 7 B 8 D 9 B 10 C 11 D 12 A 13 A 14 D 15 A 16 B 17 D 18 D 19 C 20 B 21 A 22 A 23 D 24 A 25 C 26 C 27 A 28 A 29 D 30 B 31 D 32 B 33 D 34 B 35 C 36 D 37 A 38 B 39 B 40 B 41 C 42 A 43 B 44 B 45 C 46 B 47 D 48 B 49 B 50 D 51 A 52 C 53 B 54 A 55 B 56 C 57 AD 58 ABC 59 A 60 BCD 61 BC 62 BD 63 AC 64 AD 65 ABC 66 A 67 A 68 B 69 C 70 A 71 B 72 B 73 C 74 A 75 B 76 A 77 A 78 A 79 A 80 B CEMISTRYWRLD.I Page 14