Questions on Addition Reactions (Organic Chemistry)
20 multiple-choice questions on Addition Reactions in Organic Chemistry, each with five answer choices (A–E). At the end, you’ll find a complete answer key with extended explanations.
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Multiple Choice Questions: Addition Reactions (Organic Chemistry)
1. What is an addition reaction?
A) A reaction where atoms are removed from a molecule
B) A reaction where atoms are added to a multiple bond
C) A reaction involving oxidation only
D) A substitution of hydrogen
E) A combustion reaction
2. Which types of compounds typically undergo addition reactions?
A) Alkanes
B) Aromatic rings
C) Saturated hydrocarbons
D) Alkenes and alkynes
E) Alcohols
3. What is formed when hydrogen is added to an alkene?
A) An alkyne
B) An aromatic compound
C) An alcohol
D) An alkane
E) A ketone
4. What catalyst is commonly used for the hydrogenation of alkenes?
A) HCl
B) NaOH
C) Pt or Pd
D) H₂O
E) FeCl₃
5. What is the product of the reaction of ethene with Br₂?
A) Ethyne
B) 1,2-dibromoethane
C) Ethanol
D) Ethanal
E) Bromobenzene
6. What type of addition reaction involves water adding to an alkene?
A) Hydration
B) Hydrolysis
C) Hydrogenation
D) Halogenation
E) Polymerization
7. In hydrohalogenation of alkenes, what is added across the double bond?
A) Water
B) A halogen molecule
C) H and OH
D) H and X (halogen)
E) Two H atoms
8. What is Markovnikov's rule?
A) The heavier atom adds to the more substituted carbon
B) The more electronegative atom bonds to the terminal carbon
C) In asymmetric alkenes, H adds to the carbon with more H atoms
D) H always adds to the more substituted carbon
E) OH adds to the carbon with fewer hydrogens
9. Which compound is formed when HBr is added to propene (CH₃CH=CH₂)?
A) CH₃CH₂CH₂Br
B) CH₃CHBrCH₃
C) CH₂BrCH₂CH₃
D) CH₃CH=CHBr
E) CH₃CH₂CHBr₂
10. What type of reaction is the addition of Cl₂ to cyclohexene?
A) Electrophilic substitution
B) Nucleophilic addition
C) Electrophilic addition
D) Free radical substitution
E) Oxidation
11. Which of the following is not an addition reaction?
A) Halogenation of an alkene
B) Hydration of an alkene
C) Hydrogenation of an alkene
D) Combustion of an alkene
E) Hydrohalogenation of an alkene
12. What is the first step in the electrophilic addition mechanism to an alkene?
A) Formation of carbocation
B) Nucleophile attack
C) Double bond breaks
D) Electrophile attacks the double bond
E) Formation of alkyl halide
13. Which of the following is an example of anti-Markovnikov addition?
A) HCl addition to ethene
B) HBr addition to propene with peroxide
C) Br₂ addition to ethene
D) Water addition to 2-butene
E) H₂ addition to alkyne
14. Which of the following reagents is required for hydration of an alkene?
A) H₂O and H₂SO₄
B) NaOH and H₂
C) Br₂ and CHCl₃
D) Cl₂ and UV light
E) NaBH₄ and H₂O
15. Which of the following is true about addition reactions?
A) They decrease the saturation of molecules
B) They involve only oxygen atoms
C) They increase saturation
D) They occur only with alkynes
E) They are reversible
16. The addition of hydrogen halides to unsymmetrical alkenes follows which rule?
A) Hund’s Rule
B) Le Chatelier’s Principle
C) Markovnikov’s Rule
D) Boyle’s Law
E) Dalton’s Law
17. What product is formed when H₂ is added to 2-butene in the presence of a Pt catalyst?
A) 1-butene
B) 2-butyne
C) Butane
D) 2-butanol
E) 2-bromobutane
18. What type of bond is broken in addition reactions to alkenes?
A) Sigma bond
B) Pi bond
C) Hydrogen bond
D) Ionic bond
E) Covalent polar bond
19. Which product is expected from the halogenation of 1-butene with Br₂?
A) 1-bromo-2-butene
B) 2,3-dibromobutane
C) 1,1-dibromobutane
D) 1,2-dibromobutane
E) Butadiene
20. What is the effect of peroxide in the addition of HBr to alkenes?
A) Speeds up the reaction
B) Causes the addition to follow Markovnikov’s rule
C) Converts the reaction into elimination
D) Causes the reaction to follow anti-Markovnikov’s rule
E) No effect at all
- Questions on Amines (Organic Chemistry)
- Questions on Alkyl Halides (Organic Chemistry).
- Questions about Substitution Reactions (Organic Chemistry)
✅ Answer Key with Extended Explanations
1. B – Addition reactions involve adding atoms to a multiple bond, typically a double or triple bond.
2. D – Alkenes and alkynes, which are unsaturated, undergo addition.
3. D – Adding hydrogen to an alkene results in an alkane.
4. C – Catalysts like Pt (platinum) or Pd (palladium) are used in hydrogenation.
5. B – Ethene + Br₂ → 1,2-dibromoethane, via electrophilic addition.
6. A – Adding water to alkenes is called hydration.
7. D – H and X (halogen) are added in hydrohalogenation.
8. C – Markovnikov’s rule: the hydrogen adds to the carbon with more hydrogens.
9. B – HBr + propene follows Markovnikov’s rule, forming CH₃CHBrCH₃.
10. C – Cl₂ addition to alkenes is electrophilic addition.
11. D – Combustion is not an addition reaction; it’s a redox process.
12. D – The first step is attack of electrophile on the double bond.
13. B – In the presence of peroxides, HBr adds in anti-Markovnikov fashion.
14. A – Hydration requires H₂O and an acid catalyst (like H₂SO₄).
15. C – Addition reactions increase saturation by converting double/triple bonds to single.
16. C – Markovnikov’s rule governs addition to unsymmetrical alkenes.
17. C – Hydrogenation of 2-butene yields butane.
18. B – The pi bond of the alkene is broken in addition reactions.
19. D – Br₂ adds across the double bond of 1-butene → 1,2-dibromobutane.
20. D – Peroxides make HBr add in anti-Markovnikov orientation.
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