Tutorial 9 — Carboxylic Acids and Derivatives

Note: This tutorial PDF consists primarily of scanned images. The questions below are reconstructed based on typical FAD1018 Tutorial 9 content on Carboxylic Acids and their Derivatives.

Learning Outcomes

Understand structure and properties of carboxylic acids
Learn preparation methods for carboxylic acids
Study reactions of carboxylic acids
Understand carboxylic acid derivatives (esters, amides, acid chlorides, anhydrides)
Learn nucleophilic acyl substitution reactions

Part A: Carboxylic Acids

Question 1

a) Explain the hydrogen bonding in carboxylic acids and how it affects their physical properties.

b) Why do carboxylic acids have higher boiling points than alcohols of similar molecular weight?

c) Explain the dimeric structure of carboxylic acids in non-polar solvents.

Question 2

a) Compare the acidity of the following compounds:

Formic acid (HCOOH)
Acetic acid (CH₃COOH)
Chloroacetic acid (ClCH₂COOH)
Trifluoroacetic acid (CF₃COOH)

b) Explain the trend using inductive effects.

c) Why is chloroacetic acid stronger than acetic acid?

Part B: Preparation of Carboxylic Acids

Question 3

Complete the following reactions showing the preparation of carboxylic acids:

a) Primary alcohol oxidation: $$R-CH_2OH \xrightarrow{[O]} ?$$

b) Aldehyde oxidation: $$R-CHO \xrightarrow{[O]} ?$$

c) Nitrile hydrolysis: $$R-CN \xrightarrow{H_3O^+,\ heat} ?$$

d) Grignard reaction with CO₂: $$R-MgX + CO_2 \rightarrow ? \xrightarrow{H_3O^+} ?$$

Question 4

a) Show how to convert bromoethane to propanoic acid using a Grignard reagent.

b) Why can't a Grignard reagent be prepared from a compound containing a carboxylic acid group?

Part C: Reactions of Carboxylic Acids

Question 5

Complete the following reactions:

a) Esterification: $$CH_3COOH + CH_3OH \xrightarrow{H^+} ?$$

b) Formation of acid chloride: $$CH_3COOH + SOCl_2 \rightarrow ?$$

c) Formation of anhydride: $$2CH_3COOH \xrightarrow{P_2O_5} ?$$

d) Reduction with LiAlH₄: $$CH_3COOH \xrightarrow{LiAlH_4} ?$$

Question 6

a) What is the Hell-Volhard-Zelinsky (HVZ) reaction?

b) Write the mechanism for the HVZ reaction with propanoic acid.

c) What is the synthetic utility of this reaction?

Part D: Carboxylic Acid Derivatives

Question 7

a) Arrange the following derivatives in order of decreasing reactivity toward nucleophilic acyl substitution:

Acid chloride
Anhydride
Ester
Amide

b) Explain the reactivity order based on:

Leaving group ability
Resonance stabilization
Electrophilicity of carbonyl carbon

Question 8

Complete the following reactions:

a) Acid chloride with alcohol: $$CH_3COCl + CH_3CH_2OH \rightarrow ?$$

b) Anhydride with amine: $$(CH_3CO)_2O + CH_3NH_2 \rightarrow ?$$

c) Ester hydrolysis (acidic): $$CH_3COOCH_3 + H_2O \xrightarrow{H^+} ?$$

d) Ester hydrolysis (basic/saponification): $$CH_3COOCH_3 + NaOH \rightarrow ?$$

e) Amide hydrolysis: $$CH_3CONH_2 + H_2O \xrightarrow{H^+} ?$$

Part E: Esters and Amides

Question 9

a) What is transesterification? Give an example.

b) Why does the equilibrium in esterification reactions favor the ester under certain conditions?

c) Calculate the amount of methyl acetate formed when 1 mol of acetic acid reacts with 1 mol of methanol (Kc = 4.0).

Question 10

a) Compare the basicity of amines and amides.

b) Why is acetamide much less basic than methylamine?

c) Explain why amides are relatively resistant to hydrolysis compared to esters.

Part F: Named Reactions

Question 11

a) Describe the Claisen condensation.

b) What is the Gabriel synthesis? What is its significance in amine synthesis?

c) Explain the Hofmann rearrangement mechanism.

Key Concepts

Carboxylic Acid — R-COOH functional group
Ester — R-COO-R' functional group
Amide — R-CONH₂ functional group
Acid Chloride — R-COCl functional group
Anhydride — (R-CO)₂O functional group
Nucleophilic Acyl Substitution — Characteristic reaction of acid derivatives
Esterification — Formation of esters from acids and alcohols
Saponification — Base-catalyzed ester hydrolysis

FAD1018 Tutorial 9 — Carboxylic Acids and Derivatives