Multiple Choice Questions on Organic Reaction Mechanism Pdf

MCQ on Reaction Mechanism for NEET

To help Chemistry students to  make the most of their time and prepare effectively for their Chemistry exam, To do well in these Multiple Choice Questions on Organic Chemical Mechanism. students must be good at the basic concepts and should have knowledge about all the important Concepts of Reaction Mechanism. We are providing here the important MCQ on Reaction Mechanism for NEET. All these MCQs are provided with answers.


Reaction Mechanism MCQ Questions and Answers  : 

1. In SN1 the first step involves the formation of_________

(1) free radical

(2) carbanion

(3) carbocation

(4) final product

Answer: 3


2. The relative reactivities of acyl compounds towards nucleophillic substitution are in the order of_________

(1) Acid anhydride >Amide > Ester >Acyl chloride

(2) Acyl chloride >Ester>Acid anhydride > Amide

(3) Acyl chloride >Acid anhydride >Ester> Amide

(4) Ester >Acyl chloride>Amide >Acid anhydride

Answer: 3


3. Toluene is more reactive than benzene towards electrophilic reagents due to____________

(1) Inductive effect only

(2) Hyperconjugative effect only

(3) Both inductive as well as hyperconjugative effects

(4) Strong mesomeric effect

Answer: 3


4. Nitration of benzene is___________

(1) nucleophilic substitution

(2) nucleophilic addition

(3) electrophilic substitution

(4) electrophillic addition

Answer: 3


5. The major product obtained from the heating of 3,3–dimethyl –1– butanol with H2SO4 is___________

(1) 3, 3–dimethyl–1–butene

(2) 2, 3–dimethyl–2–butene

(3) 2, 3–dimethyl–1–butene

(4) cis and trans isomers of product (2)

Answer: 2


6. With conc. HBr ethyl phenyl ether yields________

(1) Phenol and ethyl bromide.

(2) Bromobenzene and ethanol

(3) Phenol and ethane

(4) Bromobenzene and ethane

Answer: 1


7. Which alcohol produces turbidity with Lucas reagent most slowly_________

(1) 2–Butanol

(2) t–Butyl alcohol

(3) Isobutyl alcohol 

(4) Diphenylcarbinol

Answer: 3


8. The chain propagating step is fastest in the reaction of an alkane with__________

(1) Fluorine free radical 

(2) Chlorine free radical

(3) Iodine free radical 

(4) Bromine free radical

Answer: 1


9. In the nitration of propane, the product obtained in maximum yield is___________

(1) 1–nitropropane 

(2) 2-nitropropane

(3) Nitroethane 

(4) Nitromethane

Answer: 2


10. Only two isomeric monochloro derivatives are possible for (exclude stereo isomers)________

(1) n-butane

(2) 2, 4-dimethyl pentane

(3) benzene

(4) 2-methyl butane

Answer: 1


11. The preparation of ethers from alcohols by using sulphuric acid is called_______

(1) Williamson's ether Synthesis

(2) Williamson's continuous etherification process

(3) Ziesel's method

(4) Zerewitinoff method

Answer: 2


12. The reaction of ethyl iodide with sodium ethoxide is________

(1) An electrophilic substitution reaction

(2) A nucleophilic addition reaction

(3) A nucleophilic substitution reaction

(4) A free radical substitution reaction

Answer: 3


13. The Williamson synthesis involves_______

(1) A nucleophilic addition

(2) An electrophilic substitution

(3) SN2 displacement

(4) SN1 displacement

Answer: 3


14. An unknown alcohol is treated with the "Lucas reagent' to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism____________

(1) secondary alcohol by SN1

(2) tertiary alcohol by SN1

(3) secondary alcohol by SN2

(4) tertiary alcohol by SN2

Answer: 2


15. The reactivity of alkyl halides in E2 elimination reactions follows the order_________

(1) R–I < R–Br < R–Cl < R–F

(2) R–F < R–Cl < R–Br < R–I

(3) R–I > R–Cl > R–Br < R–F

(4) R–I < R–Br < R–F < R–Cl

Answer: 2


16. The unimolecular elimination involves formation of_________

(1) A free radical 

(2) A carbanion

(3) A carbocation

(4) A biradical

Answer: 3


17. Which of the following alkyl bromides will eliminate HBr fastest_____________

(1) Ethyl bromide

(2) Propyl bromide

(3) Isopropyl bromide 

(4) t-Butyl bromide

Answer: 4


18. 1–phenyl-2-chloropropane on treating with alc. KOH gives mainly_________

(1) 1-phenylpropene

(2) 2-phenylpropene

(3) 1-phenylpropan-2-ol

(4) 1-phenylpropan-1-ol

Answer: 1


19. Which of the following alkyl halides gives a mixture of alkenes on dehydrohalogenation___________

(1) n–Propyl halide

(2) Isopropyl halide

(3) s–Butyl bromide

(4) t–Butyl bromide

Answer: 3


20. SN1 reaction on optically active substrates mainly gives________

(1) Retention in configuration

(2) Inversion in configuration

(3) Racemise product

(4) No product

Answer: 3


21. The hydrolysis of alkyl halides by aqueous NaOH is best termed as_________

(1) electrophilic substitution reaction

(2) electrophilic addition reaction

(3) nucleophilic addition reaction

(4) nucleophilic substitution reaction

Answer: 4


22. Reaction of sodium ethoxide and ethyl iodide will give___________

(1) Ether

(2) Ethyl alcohol

(3) Acetaldehyde

(4) Acetic acid

Answer: 1


23. When two mole of alcohol reacts with 1 mole of ketone, it gives________

(1) Hemiacetal

(2) Acetal

(3) Hemiketal

(4) Ketal

Answer: 4


24. When acetone reacts with Grignard reagent followed by hydrolysis, it gives__________

(1) 1° –alcohol 

(2) 2° –alcohol

(3) 3° –alcohol

(4) Methyl alcohol

Answer: 3


25. Reaction of HBr with propene in the presence of peroxide gives___________

(1) 3–bromo propane 

(2) Allyl bromide

(3) n–propyl bromide 

(4) Isopropyl bromide

Answer: 3


26. The compound that will react most readily with gaseous bromine has the formula__________

(1) C4H10

(2) C2H4

(3) C3H6

(4) C2H2

Answer: 3 


27. Which of the following ether can not be prepared by Williamson's method__________

(1) Ditertbutyl ether

(2) Ethyl-tert-butyl ether

(3) Anisole

(4) 1 & 2 Both

Answer: 1


28. Which of the following compounds will not undergo Friedal-Craft's reaction easily________

(1) Toluene

(2) Cumene

(3) Xylene

(4) Nitrobenzene

Answer: 4


29. Which of the following can be used as the halide component for Friedel-Crafts reaction ?

(1) Chloroethene

(2) Isopropyl chloride

(3) Chlorobenzene 

(4) Bromobenzene

Answer: 2


30. Among the following compounds the one that is most reactive towards electrophilic nitration is_________

(1) Toluene

(2) Benzene

(3) Benzoic Acid

(4) Nitrobenzene

Answer: 1


31. The order of decreasing reactivity towards electrophilic reagent for the following______

(a) Benzene

(b) Toluene

(c) Chloro benzene

(d) Phenol

(1) b > d > a > c 

(2) d > c > b > a

(3) d > b > a > c 

(4) a > b > c > d

Answer: 3


32. For the following :

(a) I–   (b) Cl–    (c) Br–

the increasing order of nucleophilicity would be______________

(1) Cl– < Br– < I–

(2) I– < Cl– < Br–

(3) Br– < Cl– < I–

(4) I– < Br– < Cl–

Answer: 1


33. Nitration of aniline in strong acidic medium also gives m-nitroaniline because_________

(1) In spite of substituents nitro group always goes to only m-position.

(2) In electrophilic substitution reactions amino group is meta directive.

(3) In absence of substituents nitro group always goes to m-position

(4) In acidic (strong) medium aniline is present as anilinium ion.

Answer: 4


34. Which of the following reagents would distingusih cis-cyclopentane-1,2-diol from its trans-isomer?

(1) Acetone

(2) Ozone

(3) MnO2

(4) Aluminium isopropxide

Answer: 1


35. The product formed by the reaction of an aldehyde with a primary amine is_________

(1) Schiff base

(2) Ketone

(3) Carboxylic acid

(4) Aromatic acid

Answer: 1


36. Consider the nitration of benzene using mixed conc. H2SO4 and HNO3. If a large amount of KHSO4is added to the mixture, the rate of nitration will be_______

(1) faster

(2) slower

(3) unchanged

(4) doubled

Answer: 2


37. In an SN¹ reaction on chiral centres, there is___________

(1) 100% retention

(2) 100% inversion

(3) 100% racemization

(4) inversion more than retention leading to partial recemization

Answer: 4


38. Reaction of carbonyl compound with one of the following reagents involves nucleophilic addition followed by elimination of water. The reagent is_________

(1) hydrocyanic acid

(2) sodium hydrogen sulphite

(3) a Grignard reagent

(4) hydrazine in presence of feebly acidic solution

Answer: 4


39. Halogenation of alkanes gives a mixture of monohalo products. The ease of substitution follows the order__________

(1) Tertiary H > primary H > secondary H

(2) Primary H < secondary H < tertiary H

(3) Primary H > secondary H > tertiary H

(4) Secondary H > tertiary H < primary H

Answer: 2


40. The number of different substitution products possible when ethane is allowed to react with bromine in sunlight are_____________

(1) 9

(2) 6

(3) 8

(4) 5

Answer: 1