Types of Reactions Substitution Addition Elimination - UNSOLVED PRACTICE SET

Q7. Differentiate between nucleophilic substitution (SN1 and SN2) and electrophilic substitution with one example of each.

Q8. Explain Markovnikov's rule with an example. Why does HBr add to propene to give 2-bromopropane as the major product?

Q9. What is Saytzeff's rule? Illustrate with the dehydrohalogenation of 2-bromobutane.

Q10. Why does benzene undergo electrophilic substitution rather than electrophilic addition, despite having double bonds?

Q11. Your school lab prepares ethene from ethanol using concentrated sulphuric acid. Identify the type of reaction and write the balanced chemical equation.

Q12. Distinguish between SN1 and SN2 mechanisms with respect to:

(a) The nature of the substrate

(b) The role of the solvent

(c) The stereochemistry of the product

Q13. Discuss the different types of organic reactions with examples:

(a) Substitution reactions — nucleophilic substitution (SN1, SN2), electrophilic substitution, free radical substitution

(b) Addition reactions — electrophilic addition (Markovnikov and anti-Markovnikov), nucleophilic addition, free radical addition

(c) Elimination reactions — E1 and E2 mechanisms, Saytzeff's rule, Hofmann elimination

(d) For each type, give one example with a complete mechanism using curved arrows

Q14. Explain the mechanism of the following reactions in detail:

(a) Electrophilic addition of HBr to propene (Markovnikov addition) — show carbocation formation and stability

(b) Nucleophilic substitution of CH₃Br by OH⁻ (SN2 mechanism) — show backside attack and inversion of configuration

(c) Elimination of HBr from 2-bromobutane using alcoholic KOH (E2 mechanism) — show formation of 2-butene as major product

Use curved arrows to show electron movement in each step.

Q15. Understanding reaction types is essential for India's chemical and pharmaceutical industries. Discuss:

(a) How substitution reactions are used in the synthesis of dyes (like indigo) in the Indian textile industry

(b) Why addition reactions are important in the hydrogenation of vegetable oils to make vanaspati ghee

(c) How elimination reactions are used in the petrochemical industry to produce alkenes from alkanes

(d) The environmental implications of these reactions and green chemistry alternatives being adopted in India

Q16. A mixture contains 1-bromopropane and 2-bromopropane. When treated with aqueous KOH:

(a) Write the substitution products formed from each bromopropane.

(b) Identify which bromopropane would react faster by SN2 mechanism and explain why.

(c) If the reaction is carried out with alcoholic KOH instead, what type of reaction would occur and what products would form?

Q17. In the addition of HBr to 3-methyl-1-butene:

(a) Draw the structure of 3-methyl-1-butene.

(b) Show the two possible carbocation intermediates formed after protonation.

(c) Identify the more stable carbocation using hyperconjugation and predict the major product according to Markovnikov's rule.

Q18. A pharmaceutical company in Hyderabad produces paracetamol using a multi-step synthesis. One step involves the nitration of phenol (electrophilic substitution) followed by reduction to form p-aminophenol, which is then acetylated (nucleophilic substitution).

(a) Write the balanced equation for the nitration of phenol showing the electrophile (NO₂⁺) and the major product.

(b) In the acetylation step, p-aminophenol reacts with acetic anhydride ((CH₃CO)₂O). Identify the nucleophile and electrophile in this step and write the product formed.

(c) If the overall yield from phenol to paracetamol is 65%, calculate the mass of paracetamol obtained from 100 g of phenol.

[Given: Molar masses: Phenol = 94 g/mol, Paracetamol = 151 g/mol]