Reaction Mechanism Exercise # 1

Exercise # 1 1. 2. [Single Correct Choice Type Questions] Consider the chemical reaction, 2A (g)  B(g) + 3C(g) The rate of this reaction can be expressed in terms of time derivatives of conc. of A(g) , B(g) or C(g). Identify the correct relationship amongst rate expressions : (A) Rate = – d [A] d [B] d [C] = = dt dt dt (B) Rate = 1 d [A] d [B] 1 d [C] = = 2 dt dt 3 dt (C) Rate = – 1 d [A] d [B] 1 d [C] = = 2 dt 3 dt dt (D) Rate = d [B] 1 d [A] 1 d [C] =– =– 2 dt 3 dt dt K The differential rate law equation for the elementary reaction A + 2B  3C, is : (A) – d [A] d [B] d [C] =– = = k [A] [B]2 dt dt dt (B) – d [A] 1 d [B] 1 d [C] =– = = k [A]2 [B] dt 2 dt 3 dt (C) – d [A] 1 d [B] 1 d [C] =– = = k [A] [B]2 dt 2 dt 3 dt (D) None of these 3. The minimum energy for molecules to enter into chemical reaction is called. (A) Kinetic energy (B) Potential energy (C) Threshold energy (D) Activation energy 4. For an elementary process 2X + Y  Z + W, the molecularity is : (A) 2 (B) 1 (C) 3 (D) Unpredictable What is the order of a reaction which has a rate expression rate = k [A]3/2[B]–1 ? (A) 3/2 (B) 1/2 (C) 0 (D) None of these 5. 6. Following mechanism has been proposed for a reaction. 2A + B  D + E Step -1 A + B  C + D – (slow) Step -2 A + C  E – (fast) The rate law expression for the reaction is : (A) rate = K[A]2 [B] (B) rate = K [A] [B] (C) rate = K [A]2 (D) rate = K[A][C] 7. Activation energy of a reaction is : (A) The energy released during the reaction (B) The energy evolved when activated complex is formed (C) Minimum amount of energy needed to overcome the potential barrier of reaction (D) The energy needed to form one mole of the product. 8. Catalyst increases the rate of reaction because : (A) it decreases H (C) it decreases activation energy (B) it increases H (D) it increases activation energy Which of the following is not a Nucleophile ? (A) AICI3 (B) (CH3)2 NH (C) C2H5OH 9. 10. (D) H2O Which one of the following has maximum nucleophilicity ? (A) CH3 S  (B) (C) Et3N (D) REACTION MECHANISM 11. 12. 13. Which one of the following has minimum nucleophilicity ? (A) (CH3)3CLi (B) NaNH2 (C) CH3ONa (D) NaOH Which of the following is an electrophilic reagent ? (A) H2O (B) OH– (C) NO2+ (D) None (C) Br– (D) I– Best leaving group is : (A) F– 14. (B) Cl– The correct order of leaving ability is : (A) > H2O (B) > (C) > 15. Substitution reactions involve : (A) Cleavage of a s–bond and formation of a new s–bond (B) Cleavage of two s–bond and formation of a new p –bond (C) Cleavage of a p–bond and formation of two new s –bond (D) None of these 16. Which of the following reaction is a substitution reaction ? Ni / H2  CH3–CH3 (A) CH2 = CH2     (C) CH3 – I + OH  CH3 OH  I 17. 18. 19. 20. 21. > Zn (B) CH 2– CH2   CH2 = CH2 + ZnBr2 Br Br H KCN     CH – C –OH (D) CH – CHO  3 3 H CN SN1 reactions occur through the formation of intermediate : (A) Carbocation (B) Carbanion (C) Free radical (D) None of these Which of the following is protic solvent ? (A) Acetone (B) Ethanol (C) DMF (D) Ether Which of the following is aprotic solvent ? (A) DMSO (B) NH3 (C) H2O (D) CH3COOH Which solvent is non-polar solvent ? (A) CH3 –CO–CH3 (B) CH3–SO –CH3 (C) CH3COOH (D) Cyclohexane In an SN1 reaction, the configuration of the product undergoes : (A) inversion 22. (D) (B) racemization (C) retention Which of the following alkyl halide is most reactive towards H2O ? (A) (B) (C) (D) (D) difficult to predict HCl / ZnCl2    [X] 23. Identify X and the mechanism of the reaction. (A) CH3 – CH2 – CH2 – CH2 – Cl & SN1 (B) CH3 – CH2 – CH2 – CH2 – Cl & SN2 (C) CH3  CH  CH2  CH3 & SN1 | Cl (D) CH3  CH  CH2  CH3 & SN2 | Cl 24. HBr CH 3 (CH 2 ) 2 CH 2 OH  X, 1- butanol Identify X and the mechanism of the reaction (A) CH3 – CH2 – CH2 – CH2 – Br & SN1 (B) CH3 – CH2 – CH2 – CH2 – Br & SN2 (C) CH3  CH  CH2  CH3 & SN1 | Br (D) CH3  CH  CH2  CH3 & SN2 | Br PCl 5    (X) , X is : 25. (A) 26. (B) (D) What is the final product of reaction. CH3 –CH 2 – I Na   CH3 – C  CH   Product (A) CH2=CH–CH2–CH3 (C) CH  C – CH2  CH2  CH3 (B) CH3–CH2–CC–CH2–CH3 (D) CH3  C  C  CH2  CH3 H O 2 ‘Y’ Product : AgNO 27. 3 (A) 28. (C) (B) (C) (D) (C) Free radical (D) Carbanion SN2 mechanism proceeds through intervention of : (A) Carbonium ion (B) Transition state REACTION MECHANISM 29. 30. When the concentration of alkyl halide is tripled and the concentration of reaction increases by: (A) 3 times (B) 2 times (C) 1.5 times ion is reduced to half, the rate of SN2 (D) 6 times The reaction O + Nu R–C – O R–C X +X Nu – is slowest when X is : O + Nu R–C – O R–C X (A) Cl 31. 32. – (B) NH2 (C) OC2H5 (D) OCOCH3 O || NaNH2 CH 3–CH 2– C – OCH3  X, X is  O || (A) CH3–CH2– C – ONa O || (B) CH3–CH2– C – NH2 O || (C) CH 3– C – NH–CH3 (D) CH 3– CH2–NH2 Which of the following reaction is SN2Ar reaction ?   +H + Br (A) Cl NO2 (B)  + OH (C) CH3 CH3  + NO2 NO2  +H OH  33. +X Nu + Cl   (D) OH+ Br Br + OH NO2 The given reaction most likely occurs by which of the following mechanism ? CH O  3    (A) SN1 34. (B) SN2 (C) SN2Th (D) SN2Ar Electrophilic substitution reaction is characterstics reaction of (A) Alkane (B) Alkyl halide (C) Alkene (D) Aromatic compound 35. Which of the following compound gives fastest SN2 Ar reaction ? Cl Cl Cl NO2 (A) (B) (C) (D) NO2 NO2 36. 37. Which of the following compounds is least reactive in the nucleophilic aromatic substitution reaction with NaOH? (A) p-nitrofluorobenzene (B) p-nitrochlorobenzene (C) p-nitrobromobenzene (D) p-nitroiodobenzene The following reaction is : FeBr 3 C 6H6  Br2    C 6H5Br  HBr (A) An electrophilic addition reaction (B) A nucleophilic substitution reaction (C) An electrophilic substitution reaction (D) A free radical substitution reaction AlCl 3   Product 38. (A) 39. (B) (C) (D) Which of the following is the major product for the given reaction ? h + Br2   333 K (A) 2-Bromo-2-methylpentane (C) 4-Bromo-2-methylpentane (B) 1-Bromo-2-methylpentane (D) 3-Bromo-2-methylpentane 40. Addition reactions involve (A) Cleavage of a -bond and formation of a new -bond (B) Cleavage of two -bond and formation of a new -bond (C) Cleavage of a -bond and formation of two new -bond (D) None of these 41. Which is the correct decreasing order of reactivity in the following ? (I) CH2=CH2 (II) CH3–CH=CH2 (III) (CH3)2C=CH2 (A) III > I > II (B) III > II > I (C) II > III > I 42. (D) I > II > III Cl 2 / h Which type of substitution in the given reaction occurs R–H    R–Cl (A) Free radical substitution (C) Nucleophilic substitution (B) Electrophilic substitution (D) All of these REACTION MECHANISM 43. Which is the most reactive alkane towards bromination in presence of sunlight ? (A) CH3CH3 44. 45. (B) CH4 (C) CH3CH2CH3 (D) h CH3–CH2–CH2–CH3 + Cl2   Major product : (A) CH3–CH2–CH2–CH2–Cl (B) (C) (D) dil. H SO 4 Ph – CH2 – CH = CH2  2    X, Identify product 'X' is : (B) Ph–CH2–CH–CH3 (A) Ph – CH2 – CH2 – CH2 – OH OH (C) Ph–CH–CH2–CH3 (D) Ph – CH2 – OH OH 46. + Br2 P, P will have configuration : Br Br (A) (B) (C) both are true Br 47. Br HOCl CH3CH2CH=CH2   Product, Product is : (A) (B) (C) (D) (i ) CH MgBr  3  Product is : (ii ) H O 48. 2 (A) (B) (C) (D) (D) none is true 49. HCN CH3CHO   Product is : (A) (B) (C) Both (A) and (B) (D) None of these R O2  Product is : + HBr 2  50. 51. 52. (A) (B) (C) (D) What is the product when one mole of pent-1-yne treated with two moles of HCl ? (A) 1,2-Dichloropentane (B) 2,3-Dichloropentane (C) 1,1-Dichloropentane (D) 2,2-Dichloropentane The correct order of reactivity of CH3MgBr with following compounds will be : CH3–CHO, HCHO, (1) (2) (A) 2 > 1 > 4 > 3 53. (B) 4 > 3 > 1 > 2 Ph–CHO (3) (C) 2 > 1 > 3 > 4 Which of the following is free radical addition reaction ? (A)  + NO2 (B) CH2 = CH2 + HBr  CH3 –CH2 – Br R 2O 2 (C) CH3 – CH = CH2 + HBr   CH3 – CH2 – CH2 –Br (D) CH3 – CH = CH2 + HCl  CH3 – CH – CH3 | Cl (4) (D) 1 > 3 > 2 > 4 REACTION MECHANISM 54. Which of the following reaction is an elimination reaction ? PCl 5  CH3 – CH2 – CH2 – Cl (A) CH3 – CH2 – CH2 – OH  HCl (B) CH3 – CH = CH2   Alc . KOH   CH3 – CH = CH2 (C) CH OH 3    (D) 55. The relative rate of acid catalysed dehydration of following alcohols would be : CH3 | C – Ph | OH IV (A) III > I > IV > II 56. (B) III >IV > I > II (C) I > III > IV > II 2-Chlorobutane on treatment with alcoholic KOH/ gives mainly (A) 2-Butene (B) 1-Butene (C) 2-Butanol 57. (D) IV > III > I > II (D) 1-Butyne Major Product is : (A) CH 3–C=CH–CH 3 (B) CH 3–CH–CH=CH 2 CH3 CH3 OH 58. (C) CH 2=C–CH 2–CH 3 (D) CH3–CH–CH–CH3 CH3 CH3 Alc. KOH   X  Ph Br X is the total number of possible products in this elimination reaction : (A) 01 (B) 03 (C) 02 (D) 04 CH3 OH 59. Conc.H 2SO 4   [X] as major product In the given reaction : [X] will be : CH2 (A) 60. CH3 (B) CH3 (C) CH3 (D) Which of the following cannot undergo E2 reaction ? (A) (B) (C) (D) none of these EXERCISE - 1 1. C 2. C 3. C 4. C 5. B 6. B 7. C 8. C 9. A 10. D 11. D 12. C 13. D 14. C 15. A 16. C 17. A 18. B 19. A 20. D 21. B 22. C 23. C 24. D 25. A 26. D 27. C 28. B 29. C 30. B 31. B 32. C 33. D 34. D 35. C 36. D 37. C 38. B 39. A 40. A 53. C 41. B 54. C 42. A 55. D 43. D 56. A 44. B 57. B 45. C 58. B 46. B 59. B 47. A 60. C 48. A 49. C 50. A 51. D 52. C