Reactions - Dehydration, Oxidation, Esterification - UNSOLVED PRACTICE SET

Q7. Write the reaction for the dehydration of propan-2-ol. What is the major product according to Saytzeff rule?

Q8. Why does the oxidation of primary alcohol with KMnO₄ give a carboxylic acid, while oxidation with PCC gives an aldehyde?

Q9. Write the reaction of ethanol with ethanoic acid in presence of H₂SO₄. Name the product and the reaction.

Q10. What is the difference between dehydration and dehydrogenation of alcohols? Give one example of each.

Q11. Why is concentrated H₂SO₄ used as a catalyst in esterification rather than dilute H₂SO₄?

Q12. Your school lab has a bottle of butan-1-ol. How would you convert it to butanoic acid? Write the reaction and name the reagent.

Q13. (a) Describe the dehydration of alcohols. What are the conditions required?

(b) Explain the mechanism of acid-catalyzed dehydration of ethanol to ethene.

(c) Why does the dehydration of alcohols follow the Saytzeff rule?

(d) Compare the ease of dehydration of primary, secondary, and tertiary alcohols.

Q14. (a) Describe the oxidation of alcohols using different reagents:

(i) KMnO₄/H⁺ or K₂Cr₂O₇/H⁺

(ii) PCC

(iii) Collins reagent

What products are formed in each case for primary and secondary alcohols?

(b) Why can't tertiary alcohols be oxidized by common oxidizing agents?

Q15. (a) Describe the esterification reaction. Write the mechanism of acid-catalyzed esterification.

(b) Why is esterification a reversible reaction? How can the equilibrium be shifted towards the product?

(c) A student wants to prepare ethyl ethanoate from ethanol and ethanoic acid. Suggest conditions to maximize the yield.

Q16. A student wants to convert ethanol to different products.

(a) Write the reaction for converting ethanol to ethene by dehydration. What is the optimum temperature?

(b) Write the reaction for converting ethanol to ethanal by oxidation. What reagent is used?

(c) Write the reaction for converting ethanol to ethyl ethanoate by esterification.

(d) If the student starts with 23 g of ethanol (molar mass = 46 g/mol), calculate the theoretical yield of:

(i) Ethene (molar mass = 28 g/mol)

(ii) Ethanal (molar mass = 44 g/mol)

(iii) Ethyl ethanoate (molar mass = 88 g/mol)

(e) In practice, the student obtains 8.4 g of ethene. Calculate the percentage yield and suggest two reasons for the low yield.

Q17. The following reactions involve different alcohols:

Reaction 1: CH₃CH₂CH₂OH + PCC → Product A

Reaction 2: CH₃CH₂CH₂OH + KMnO₄/H⁺ → Product B

Reaction 3: (CH₃)₂CHOH + K₂Cr₂O₇/H⁺ → Product C

Reaction 4: CH₃CH₂OH + CH₃COOH → Product D

(a) Identify products A, B, C, and D.

(b) For Reaction 1, why is PCC preferred over KMnO₄ for oxidizing primary alcohols to aldehydes?

(c) For Reaction 2, calculate the mass of product B obtained from 30 g of propan-1-ol if the yield is 75%.

(d) For Reaction 3, if 15 g of propan-2-ol is oxidized, calculate the mass of product C obtained.

(e) For Reaction 4, if 23 g of ethanol and 30 g of ethanoic acid are used, which is the limiting reagent? Calculate the theoretical yield of product D.

Q18. In a school chemistry lab, students perform various reactions of alcohols.

(a) A student heats ethanol with concentrated H₂SO₄ at 170°C and collects a gas. The gas decolourizes bromine water. Identify the gas and write the reaction. Why does the temperature need to be carefully controlled?

(b) Another student oxidizes ethanol with acidified potassium dichromate. The solution changes from orange to green. Explain the colour change and write the reaction.

(c) A third student prepares ethyl ethanoate by refluxing ethanol and ethanoic acid with concentrated H₂SO₄. Why is reflux used? Why can't the reaction be carried out in an open beaker?

(d) The students learn that wine turns sour when exposed to air. What chemical change occurs? Write the reaction.

(e) The teacher asks: "If you were designing a breathalyser to detect drunk drivers, which property of ethanol would you measure?" Give your answer with reasoning.