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UNIT tlt, ORGANIC REACTION MECHANISMS, , 1, Which of the following is not a non-kinetic method of investigating reaction mechanisms?, , a) Identification of products b) Isotope effects, ¢) Isotopic labeling d) Isolation of an intermediate, 2. Kinetically controlled reactions have, a) lowest free energy b) lower free energy of activation, c) lowest free energy of equilibrium d) lower free energy of the isomers, 3. The rate of a Sy1 reaction is the fastest in the hydrolysis of which of the following halides?, a) CH3Br b) C.HsBr c) (CH3)CBr d) (CH3),CHBr, 4. Thermodynamic requirements for a chemical reaction are, a) AG > 0, AH > 0, AS<0 b) AG< 0, AH > 0, AS<0O, c) AG <0, AH <0, AS>0O d) AG <0, AH<0, AS<0O, 5. Thermodynamically controlled reaction is, a) lowest free energy of the product b) lower free energy of activation, c) lowest free energy of equilibrium d) highest free energy of activation, , 6. Naphthalene on sulphonation gives two products, namely a-isomer and fi-isomer. The, kinetically controlled product is, a) B-isomer b)c-isomer c) a and B isomers d) none of these, , 7. Choose the correct statements from the following regarding intermediates., 1) Intermediates are normal covalent molecules, 2) It possesses a definite geometry, 3) It can be isolated or trapped, 4) It possesses partial bonds, , a)1,2,4 b)2,3,4 c)3,4,1 d)1,2,3, 8. In nitration of benzene, the intermediate (NO,") can be detected by, , a) IR spectra b) NMR spectra c) Raman spectra d) ESR spectra, 9. Benzyne can be trapped by adding, , a) cyclopropane b) naphthalene c) any nucleophile d) anthracene, , 10. The nature of reaction as established by the figure is, , Acti, compjex, , , , , , , , E P, , R, Reaction path, @) a dark reaction b) an exothermic reaction, c) an endothermic reaction d) a photochemical reaction, , 11. Any reaction in which the reactants are all liquids, and one or more of the products is gas, the, reaction is, a) thermodynamically controlled by the increased entropy b) kinetically controlled, c) irreversible process d) reversible process

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12. Carbenes are trapped by adding, a) cyclohexene b) anthracene c) nucleophiles d) electrophiles, , 13. Choose the correct statements from the following:, 1) A plot of In K against 1/T is a linear with positive slope, 2.) AG* must be negative for the reaction to be spontaneous, 3) The enthalpy of activation for the first order reaction is Ea = AH* + RT, 4) The ionic strength effect gives information about the nature of reacting species which, gives the intermediate, a)1,2,3 b) 2, 3,4 c)1,3,4 d) 3,4, , 14, Cross over experiment is very useful to determine, , a) inter or intramolecular rearrangements _b) intermolecular rearrangements, c) intra molecular rearrangements d) rate determining step of the reaction, , 15. For a reaction of series of alkyl bromides with iodide ion,in acetone, the highest order of S,,2, reactivity is, , a) (CHs)sCCH.Br b) (CHs)2CH,CH2Br —c) CHsCH2CH,Br d) CHyCH,Br, , 16. Choose the correct statements from the following:, 1) The carbon atom of the carbonium ion is sp* hybridized with one empty p-orbital, 2.) The order of stability is RxC’ < RHC” < RH2C* < H;C”, 3) The carbonium has a flat structure with a bond angle of 109.5° between them, 4) Hyperconjugation and resonance are the important factors which increase the stability of, carbocations., , a)1,2,3 b)2,3 c)1,4 d)2,3,4, 17. Consider the following carbanions., , 1 wo XOj0 2) ox XO) 3) {O)-*, , a)1l>2>3 b)3>2>1 c)2>3>1 d)1>3>2, 18. The carbonium ion which is the most stable is, , a) (CHs)sC~ b) Phyc* c) CH,” d) CoH", 19. The rate of a S,1 reaction is the fastest in the hydrolysis of which of the following halides?, , a) CH;Br b) CH;CH,CI ¢) (CH3)sCBr d) (CHy)2CHBr, 20. In which alkyl halide S42 is the most favoured mechanism?, , a) CH;CI b) CH,CH,CI ¢) (CHs),CHCI d) (CH3)9CCI, 21. The hybridization of the carbon atom of carbocation is of the type, , a) sp b) sp? ¢) sp* d) dsp*, 22. The most stable carbene among the following is, , a) :CH2 b) s;CHCOOR c) :CHPh d) :CHBr, 23. The order of the stability of the following carbanions., , a) RyC-CH, >RyC=CH >RC=C b) RC=C >R,C=CH >RsC-CH, , c) R,C =CH >RC=C >RC-CH, d) RsC - CH” > R2C = CH” > RCS C™, , 24. Su solvolysis in alkyl halide is highly favoured in, , Cs cH,, a) cHscI b) (cHs)CcI af X d) CX, ca a

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25. Sy1 mechanism leads to, a) inversion b) retention ¢c) racimization d) meso product, , 26. The rate of hydrolysis of the following compounds follows the order, CHy, 1) He==o—e = 2) «xX 3) Hyc—cH,—er 4) Ha FH— CHa CHICH ale, Br Br, 3, a)1>2>3>4 b)2>4>3>1 c)4>3>2>1 d)3>2>4>1, 27. Which of the following compounds will be least reactive to S,1 reactions?, , GO +O 0, , 28. In the given reaction, the product ‘A’is, , aon « ll, HOH A, , Cos, Hs, Is 3, a) fo b) -. c) of. d) wo, CHs Cas Cas, , 29. Choose the correct statements from the following:, 1)in the singlet carbene, the carbon is sp* hybridized, 2) In the triplet carbene, the carbon atom is sp* hybridized, 3) In the triplet carbene, these electrons have parallel spins, 4) The triplet state of carbene is less stable than the singlet state in ground state, , a)1,2,3 b)2,3,4 ¢)2,4 d)1,2,3, , 30. In mass spectroscopy a peak at m/e = 76 indicates the formation of -------- as an intermediate., a) carbocation b) carbene c) nitrene d) benzyne, , 31. Nitrene can be trapped by addition of, a) cyclohexene b) co ¢c) cyanide ion d) benzene, , 32. Choose the false statement from the following:, 1) Nitrenes are electron-deficient monovalent nitrogen species in which the nitrogen atom, has a octet electrons in its outer shell, 2) These intermediates are detected by ESR spectroscopy, 3) Aryl nitrenes do not undergo dimerization reactions, 4) In triplet carbene, the electrons are paired, , a)1,2,3,4 b) 2,3,4 c)1,3,4 d)2,4, 33. Which of the following is least reactive in a nucleophilic substitution reaction?, a) (CHy),CCI b) CH, = CHC! c) CH;CH,Cl d) CH, = CHCH,CI, 34. Among the following reduction reactions, which one gives the free radical intermediates?, a) Clemmensen reduction b) Birch reduction, c) Wolf-Kishner reduction d) Meerwein-Ponndorff Verley reduction, , 35. Carbenes are formed by, a) B-elimination b) a-elimination c)y-elimination d) both B and y eliminations

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49. Addition of singlet carbene to trans-2-butene gives ----------- isomer, , a) cis b) trans ¢) 50% cis and 50% trans d) 60% trans and 40% cis, 50. The stable conformation of ethylene glycol is, a) anti b) gauche C) partially eclipsed d) fully eclipsed, , 51. Aryl halides are less reactive towards SN reactions as compared to alkyl halides due to, , a) formation of more stable carbocation b) resonance stabilization, c) long C—X bond d) cannot be predicted, , 52. Dehydrobrominaiton is in the order for the following compounds, , Sr 8r, 1) eA 9) ON, , a)3>2>1 b)1>2>3 c)2>3>1 d)2>1>3, 53. Cope reaction is used in the preparation of, a) alkene b) alkyne c) alcohol d) aldehyde, , 54. Which Is the major product in the following reaction?, HyC—CH—CH=CH, + HBr ————P X (Major product), , Hs, a) HyC—CH—CH—CH, b) 4;c— CH2—CHsBr, | ) we, CHs Br CHy, CHy, c) Hoyo d) none of these, CHy, 55. Which of the following reagents when treated with alkene gives a diol?, a) OsO, b) HIO,, c) Pb(OOCCHy), d) All of these, 56. When an alkene reacts with peracid, the product is, a) alkane b) alkyne, c) epoxide d) ester, 57. Arrange the given halides in the increasing order of SN1 reactivity., 1) CHyCH,CH,Cl 2)CH,=CHCH,CI 3) CH;CH,CHCICH,, a)i>2>3 b)2>1>3, c)2>3>1 d)3>2>1, 58. The correct of order of decreasing nucleophilicity is, a) AcO™ > F > RNH, > OH™ b) OH” > RNH, > F > AcO™, ¢) OH” > RNH, > AcO™ > F- d) R-NH2 > OH™ > AcO™ > F~, , 59. Order the following with respect to reactivity., , oa 0D wtF, , a) li>iii>i b)i>ii>ii, c)ilii>ti>i d)lii>i>ti