Free Elimination Reactions MCQs with Answers
19 Elimination Reactions MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Elimination reactions remove a leaving group and a hydrogen atom from adjacent carbon atoms to form an alkene. The topic covers dehydrohalogenation of alkyl halides, E1 and E2 mechanisms, the role of base, solvent and substrate structure, and Zaitsev orientation, which is often contrasted with substitution.
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19 questions
- A. an alcohol
- B. an alkane
- C. a carboxylic acid
- D. an alkene, by elimination of hydrogen halide
Explanation: In ethanol the hydroxide ion acts as a base rather than as a nucleophile, removing a hydrogen from the carbon next to the one bearing the…
Correct answer: an alkene, by elimination of hydrogen halide- A. the less substituted, less stable alkene
- B. always the cis isomer
- C. the more highly substituted and therefore more stable alkene
- D. an alkane
Explanation: When more than one alkene can form, the preferred product is the one with the greater number of alkyl groups attached to the doubly bonded…
Correct answer: the more highly substituted and therefore more stable alkene- A. a high concentration of a strong base, a non aqueous solvent and a higher temperature
- B. dilute aqueous conditions at room temperature
- C. the use of a weak nucleophile in water
- D. cooling the mixture in ice
Explanation: Elimination has the higher activation energy and produces more particles, so heat and a strong base in ethanol push the reaction that way…
Correct answer: a high concentration of a strong base, a non aqueous solvent and a higher temperature- A. Addition
- B. Elimination
- C. Base
- D. Heat
Explanation: A vicinal dihalide is converted to an alkyne by removing two molecules of hydrogen halide with hot alcoholic potassium hydroxide, which is…
Correct answer: Addition- A. first order kinetics
- B. second order kinetics
- C. third order kinetics
- D. zero order kinetics
Explanation: An E2 elimination occurs in one concerted step and its rate depends on both the substrate and the base, so the rate law contains two…
Correct answer: second order kinetics- A. the concentration of substrate
- B. the concentration of nucleophile
- C. the concentration of substrate as well as nucleophile
- D. base the concentration of substrate as well as nucleophile
Explanation: In an E1 reaction, the slow rate-determining step is ionisation of the substrate to form a carbocation, so rate = k[substrate].
Correct answer: the concentration of substrate- A. halogenation
- B. dehalogenation
- C. dehydrohalogenation
- D. hydrohalogenation
Explanation: Removal of a hydrogen atom and a halogen atom from adjacent carbon atoms is dehydrohalogenation, usually producing an alkene.
Correct answer: dehydrohalogenation- A. E1 mechanism- strong base and alkyl halide, E2 mechanism- weak base and alkyl halide
- B. E1 mechanism- weak base and alkyl halide, E2 mechanism- strong base and alkyl halide
- C. E1 mechanism- strong base and alkyl halide, E2 mechanism- strong base and alkyl halide
- D. E1 mechanism- weak base and alkyl halide, E2 mechanism- weak base and alkyl halide
Explanation: E1 mechanism- weak base and alkyl halide, E2 mechanism- strong base and alkyl halide.In the E1 mechanism, the rate-determining step is the…
Correct answer: E1 mechanism- weak base and alkyl halide, E2 mechanism- strong base and alkyl halide- A. Propene
- B. Propan-1-ol
- C. Propan-2-ol
- D. Potassium Propoxide
Explanation: a) Propene:When 2-bromopropane is heated with concentrated alcoholic potassium hydroxide (KOH), it undergoes an elimination reaction known…
Correct answer: Propene- A. C2H4
- B. C2H5OH
- C. C2H4ClOH
- D. C2H6
Explanation: A is correct option because When ethyl chloride is reacted with alcoholic KOH, ethylene is formed.
Correct answer: C2H4- A. Combustion reaction
- B. Oxidation
- C. Elimination reaction
- D. Addition reaction
Explanation: Tertiary alcohols undergo dehydration/elimination reaction to form alkenes under specific conditions i.e., heat + concentrated sulphuric…
Correct answer: Elimination reaction- A. Substitution reaction
- B. Elimination reaction
- C. Addition reaction
- D. Replacement reaction
Explanation: In elimination reactions, molecules are removed from compounds without the addition of subsequent molecules.
Correct answer: Elimination reaction- A. Electrophile
- B. Base
- C. Leaving group
- D. Acid
Explanation: Bases are proton acceptors and OH- is a base as it eliminates H+ (proton) from the reactant and forms a water molecule.
Correct answer: Base- A. Strong bases causes substitution in preference to elimination
- B. Role of leaving groups in elimination is simitar to substitution
- C. Substitution is favored more than elimination by decreasing solvent polarity
- D. Decrease in temperature will favor elimination more than substitution
Explanation: This statement is correct. In both substitution and elimination reactions, the effectiveness of the leaving group plays a crucial role; a…
Correct answer: Role of leaving groups in elimination is simitar to substitution- A. Alcoholic KOH
- B. Aqueous KOH
- C. Aqueous NaOH
- D. Alcoholic HaOH
Explanation: The suitable reagent used for dehydrohalogenation of alkyl halides would be alcoholic KOH. Here are some examples.
Correct answer: Alcoholic KOH- A. 2-Methyl propane
- B. 2-Methyl propene
- C. 2-Methyl-1 propanol
- D. 2-pentanol
Explanation: The unimolecular elimination (E1) reaction of 2-Bromo-2-methyl propane involves the removal of the bromine atom, resulting in the…
Correct answer: 2-Methyl propene- A. Nucleophilic substitution reaction
- B. Elimination reaction
- C. Nucleophilic addition
- D. None of the above
Explanation: It should be noted that whenever the reagent is alcoholic / ethanolic KOH or NaOH, the reaction that follows is elimination
Correct answer: Elimination reaction- A. Zn dust
- B. Conc. H2SO4
- C. Alcoholic KOH
- D. Aqueous KOH.
Explanation: Dehydrohalogenation of an alkyl halide is carried out in the presence of alcoholic KOH (potassium hydroxide dissolved in alcohol).
Correct answer: Alcoholic KOH- A. Substrate reaction
- B. Elimination reaction
- C. Oxidation reaction
- D. Free radical reaction
Explanation: A greater number of alkyl groups on a substrate favors elimination reactions because it leads to the formation of more stable and…
Correct answer: Elimination reactionElimination Reactions MCQs: common questions
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