Tutorial 10 — Amines and Amino Acids

Tutorial Information

Course: FAD1018 Basic Chemistry 2
Topic: Amines & Amino Acids
Semester: 2, 2024/2025
Centre: Centre for Foundation Studies in Science, Universiti Malaya

Compulsory Questions to Discuss:

Part 1: Q3 & Q4
Part 2: Q5 & Q7

PART 1: AMINES

Learning Outcome 1: Classify Primary, Secondary, and Tertiary Amines

Question 1: Give the IUPAC name for each of the following compounds and classify them as primary, secondary, or tertiary amine:

(a) [Structure diagram]

(b) [Structure diagram]

(c) [Structure diagram]

(d) [Structure diagram]

(e) [Structure diagram]

(f) [Structure diagram]

(g) [Structure diagram]

(h) [Structure diagram]

(i) [Structure diagram]

(j) [Structure diagram]

Learning Outcome 2: Draw and Name Amines According to IUPAC Nomenclature

Question 2: Draw the structural formula for each of the following compounds:

(a) N,N-dimethyl-1-butanamine

(b) 2-bromo-N-ethylaniline

(c) 3-(N-methylamino)-1-butanol

(d) Ethylmethylphenylamine

(e) Cycloheptanamine

(f) N-ethyl-N-methyl-3-propylcyclopentanamine

Learning Outcome 3: Physical Properties — Boiling Points and Solubility

Question 3: Arrange each group of compounds in order of increasing boiling point:

(a) [Compounds with structural diagrams]

(b) [Compounds with structural diagrams]

(c) n-pentane, 1-butanamine, N-ethylethanamine, 1-butanol

Compulsory to Discuss (Q3)

Learning Outcome 4: Basicity Comparison

Question 4:

a) Which type of amine (ammonia, aliphatic amines, or aromatic amines) is the most basic? Why?

b) Rank the following compounds in order of increasing basicity:

Aniline (C₆H₅NH₂)
Methylamine (CH₃NH₂)
Ammonia (NH₃)
Para-nitroaniline (C₆H₄(NO₂)NH₂)

Extracted Answer: Aliphatic amines is the most basic because the alkyl groups donate electron density to the nitrogen through induction and it makes the lone pair more available to accept a proton.

Compulsory to Discuss (Q4)

Learning Outcome 5: Preparation of Amines

Question 5: Complete the following reaction equations.

(a) [Reduction of nitrobenzene]

(b) [Nitrile reduction]

(c) [Hoffmann degradation]

(d) [Amide reduction]

(e) [Gabriel synthesis]

(f) [Alkylation of ammonia]

(g) [Reduction of azide]

Learning Outcome 6: Chemical Properties of Amines

Question 6: Explain the chemical properties with references to the reactions with acyl chloride, acid anhydrides, nitrous acid, and bromine water.

a) Write the chemical equation for the reaction between ethylamine and acetyl chloride (CH₃COCl).

b) Write the chemical equation for the reaction between ethylamine and acetic anhydride ((CH₃CO)₂O).

c) What happens when a primary amine reacts with nitrous acid (HNO₂)?

d) How does aniline react with bromine water? What is observed?

PART 2: AMINO ACIDS

Learning Outcome 1: General Structure of Amino Acids

Question 7: Draw the structures of three amino acids: Aspartic Acid, Alanine, and Lysine. Label the following parts for each amino acid:

Amino group (–NH₂)
Carboxyl group (–COOH)
Central carbon (Cα)
R group (side chain)

Learning Outcome 2: Structures of 20 Standard Amino Acids

Question 8: Of the 20 naturally occurring amino acids, identify any amino acids that exhibit the following:

(a) A cyclic structure

(b) An aromatic sidechain

(c) A side chain with a basic group

(d) A sulfur atom

(e) A side chain with an acidic group

(f) A side chain containing a proton that will likely participate in hydrogen bonding

Learning Outcome 3: IUPAC Names of Amino Acids

Question 9: What is the IUPAC name for the amino acid with the structure:

(a) [Structure diagram]

(b) [Structure diagram]

(c) [Structure diagram]

Learning Outcome 4: Zwitterion and Isoelectric Point

Question 10:

a) Define the term 'zwitterion' in amino acids.

b) What is the isoelectric point (pI) of an amino acid?

Extracted Answer: The isoelectric point (pI) of an amino acid is at the pH at which the amino acid has no net electrical change or known as zwitterion form. It can be calculated as the average of the pKa values of the amino and carboxyl groups (and additional groups if present).

Learning Outcome 5: Amino Acid Structures at Different pH

Question 11: Draw the structure of given amino acid in a medium of acidic, basic, and at pI.

A sample consisting of a mixture of three α-amino acids is being studied.

a) Electrophoresis of a mixture of lysine (pI: ~9.6), histidine (pI: ~7.6), and cysteine (pI: ~5.1) is carried out at pH 7.64.

(i.) What is electrophoresis?

Extracted Answer: Electrophoresis as a process to separate a mixture of amino acid.

(ii.) Describe the direction for which electrode that each α-amino acid would move towards (+ve terminal or -ve terminal?)

Compulsory to Discuss (Q5)

Learning Outcome 6: Reactions of Amino Acids

Question 12:

a) Write the balanced equation for the reaction of cysteine with one equivalent of NaOH.

b) Write the equation for the esterification of alanine with ethanol in acidic conditions.

c) What product is formed when serine reacts with acetyl chloride?

d) Write the reaction equation for the reaction of alanine with nitrous acid. What gas is released?

Learning Outcome 7: Peptide Bond Formation

Question 13:

a) A tripeptide can form from these α-amino acids. What is a peptide bond?

b) Draw a tripeptide that can form from lysine, histidine, and cysteine, whereby the C-terminal belongs to histidine and the N-terminal belongs to cysteine.

Compulsory to Discuss (Q7)

Learning Outcome 8: Protein Structure

Question 14:

a) Describe how the sequence of amino acids determines the primary structure of a protein and the type of bond that holds the amino acids together.

b) How do hydrogen bonds contribute to the formation of the secondary structure?

Summary: Amino Acid Classifications

Category	Amino Acids	Characteristics
Non-polar	Gly, Ala, Val, Leu, Ile, Met, Pro, Phe, Trp	Hydrophobic side chains
Polar uncharged	Ser, Thr, Cys, Tyr, Asn, Gln	Hydrophilic, no charge at pH 7
Acidic	Asp, Glu	Negative charge at pH 7
Basic	Lys, Arg, His	Positive charge at pH 7
Aromatic	Phe, Tyr, Trp	Contains benzene ring
Sulfur-containing	Cys, Met	Contains sulfur

Key Concepts

Amine — Organic derivative of ammonia (RNH₂, R₂NH, R₃N)
Primary Amine — RNH₂ (one alkyl/aryl group)
Secondary Amine — R₂NH (two alkyl/aryl groups)
Tertiary Amine — R₃N (three alkyl/aryl groups)
Amino Acid — Molecule with both amino and carboxyl groups
Zwitterion — Dipolar ion with no net charge
Isoelectric Point — pH where amino acid has no net charge
Peptide Bond — Amide bond linking amino acids
Primary Structure — Amino acid sequence in a protein
Secondary Structure — Local folding (α-helix, β-sheet)
Electrophoresis — Technique to separate charged molecules

FAD1018 Tutorial 10 — Amines and Amino Acids