Edexcel A-Level Chemistry A2 19 Organic Nitrogen Compounds Amines Amides Amino Acids and Proteins Questions

Topic 19 questions ask you to move between structures, names and reactions of amines, amides, amino acids, diazonium salts, peptides and condensation polymers.

Exam points

Draw and classify amines, amides and amino acids from names or formulae.
Explain amine basicity, solubility and salt formation using nitrogen lone pairs.
Select reagents for amine preparation, diazonium chemistry, amide and peptide reactions.

Covered syllabus points

19.1—The nomenclature of amides, amines and amino acids 19.2—The reactions of primary aliphatic amines (using butylamine as an example) and aromatic amines (using phenylamine as 19.3—Amines are miscible with water as a result of hydrogen bonding, and the reasons for the difference in basicity between 19.4—Understand, in terms of reagents and general reaction conditions, the preparation of primary aliphatic amines: i 19.5—The preparation of aromatic amines by the reduction of aromatic nitro- compounds using tin and concentrated hydrochloric 19.6—The reaction of aromatic amines with nitrous acid to form benzenediazonium ions, followed by a coupling reaction with phenol 19.7—Amides can be prepared from acyl chlorides 19.8—Describe: i condensation polymerisation for the formation of polyamides such as nylon and proteins ii addition 19.9—Draw the structural formulae of the repeat units of the polymers in 19.8 19.10—Comment on the physical properties of polyamides and the solubility in water of the addition polymer poly(ethenol) in terms 19.11—Experiments to investigate the characteristic behaviour of amino acids limited to: i acidity and basicity and the formation 19.12—CORE PRACTICAL 15 Analysis of some inorganic and organic unknowns

[Maximum number: 2]

The amino acid serine has the structure shown.

Figure for Question 1 — Edexcel A-Level Chemistry A2

(a)

The IUPAC name for serine is

2-amino-2-carboxyethanol

2-amino-1-hydroxyethanoic acid

2-amino-1-hydroxypropanoic acid

2-amino-3-hydroxypropanoic acid

[ 1 ]

(b)

Which is the organic product of the reaction between serine and sodium hydroxide solution?
A

Figure for Question (b) — Edexcel A-Level Chemistry A2

[ 1 ]

[Maximum number: 3]

Two organic compounds, A and B, are colourless liquids.
Each compound contains only one functional group.

(a)

Two tests were carried out on B.

[ 3 ]

(i)

Complete the statements in the observation and inference columns.

Table for Question (i) — Edexcel A-Level Chemistry A2

[ 2 ]

(ii)

B has a molar mass of $59 \mathrm{~g} \mathrm{~mol}^{-1}$ .

Suggest a structure for B.

[ 1 ]

[Maximum number: 3]

The synthetic drugs of the 'Caine' family are used as local anaesthetics. Caine drugs prevent nerve activity by binding to sodium channel receptors in the lipid cell membranes of neurons.

benzocaine

procaine

lidocaine

articaine

(a)

Procaine can react with hydrochloric acid to form a monohydrochloride salt.

[ 2 ]

(i)

Explain by considering both nitrogen atoms in procaine which nitrogen is more likely to be protonated in the reaction with hydrochloric acid.

Figure for Question (i) — Edexcel A-Level Chemistry A2

[ 2 ]

(b)

Lidocaine can be prepared in the synthesis shown.

Step 1

Step 3

lidocaine

[ 1 ]

(i)

Give the reagents for Step 2.

[ 1 ]

[Maximum number: 1]

The amino acid serine has the structure shown.

Figure for Question 4 — Edexcel A-Level Chemistry A2

The IUPAC name for serine is

2-amino-2-carboxyethanol

2-amino-1-hydroxyethanoic acid

2-amino-1-hydroxypropanoic acid

2-amino-3-hydroxypropanoic acid

[Maximum number: 2]

Two organic compounds, A and B, are colourless liquids.
Each compound contains only one functional group.

Two tests were carried out on B.

Complete the statements in the observation and inference columns.

Table for Question 5 — Edexcel A-Level Chemistry A2

[Maximum number: 2]

The synthetic drugs of the 'Caine' family are used as local anaesthetics. Caine drugs prevent nerve activity by binding to sodium channel receptors in the lipid cell membranes of neurons.

benzocaine

procaine

lidocaine

articaine

Procaine can react with hydrochloric acid to form a monohydrochloride salt.

Explain by considering both nitrogen atoms in procaine which nitrogen is more likely to be protonated in the reaction with hydrochloric acid.

Figure for Question 6 — Edexcel A-Level Chemistry A2

[Maximum number: 1]

Amines may be prepared by the reduction of nitriles.
Identify the nitrile and the reducing agent used to prepare butylamine.

Nitrile

Reducing agent

propanenitrile

lithium tetrahydridoaluminate(III)

propanenitrile

tin and concentrated hydrochloric acid

butanenitrile

lithium tetrahydridoaluminate(III)

butanenitrile

tin and concentrated hydrochloric acid

[Maximum number: 1]

The synthetic drugs of the 'Caine' family are used as local anaesthetics. Caine drugs prevent nerve activity by binding to sodium channel receptors in the lipid cell membranes of neurons.

benzocaine

procaine

lidocaine

articaine

Lidocaine can be prepared in the synthesis shown.

Step 1

Step 3

lidocaine

Give the reagents for Step 2.

[Maximum number: 3]

Benzoic acid is a white crystalline solid with the structure shown.

Figure for Question 9 — Edexcel A-Level Chemistry A2

It is found in many plants as it is an important building block for the biosynthesis of a variety of compounds, such as plant hormones and attractants for pollinators.

The role of benzoic acid in the chemical industry is also widespread and approximately 500000 tonnes are produced annually. It is used in the synthesis of many compounds, including medicines, dyes and insect repellents.

Such synthetic dyes are often classified as aryl azo dyes. These dyes have a range of vivid colours and a wide range of uses in many industries, including food and textiles. Their synthesis involves the formation of a diazonium ion. This ion then reacts with a phenol in a coupling reaction, to form the dye. The relative simplicity of the reactions involved and ready availability of starting materials make azo dyes cheap to produce.

Salts of benzoic acid, such as calcium benzoate and sodium benzoate, are used in the food industry as preservatives.

(a)

Benzoic acid can be used in the synthesis of azo dyes.

[ 3 ]

(i)

In Step 3, the 3-aminobenzoic acid reacts with sodium nitrite and dilute hydrochloric acid, forming a diazonium ion.

State a temperature at which this reaction should take place, giving one reason for your answer.

[ 2 ]

An explanation that makes reference to the following points:

- any temperature between $0^{\circ} \mathrm{C}$ and $10^{\circ} \mathrm{C}$ , inclusive (1)

- to prevent formation of by-products / phenol (compounds)

Mark independently

Allow just 'less than $10^{\circ} \mathrm{C}$ ' / 'below $5^{\circ} \mathrm{C}$ '

Allow to prevent decomposition of $\mathrm{HNO}_{2}$ / to prevent decomposition of diazonium ion/ diazonium ion is unstable / to prevent weak C-N bond breaking / prevent formation of (stable) nitrogen Allow reaction is too slow at temperatures below $0^{\circ} \mathrm{C} /$ low temperatures

Do not award decomposition of $\mathrm{NaNO}_{2} /$ nitro group

(ii)

Draw the structure of the azo dye formed when the diazonium ion reacts with phenol.

[ 1 ]

Figure for Answer to Question (ii) — Edexcel A-Level Chemistry A2

Ignore additional products Ignore connectivity of -OH group

Do not award if OH or COOH are at incorrect positions on ring

Do not award carboxylate ion Do not award - $\mathrm{N}_{2}$ - in between two rings

Do not award NæN

[Maximum number: 1]

This question is about the investigation of an organic compound X. X is a liquid at room temperature and pressure, which turns damp red litmus paper blue.

X reacted vigorously with ethanoyl chloride forming steamy fumes and a white solid Y.

Suggest the functional group present in Y.

N-substituted amide / -CONHR

Accept
amide / acid amide / - $\mathrm{CONH}_{2}$ / - CONH -
If name and formula are given, both must be
correct

[Maximum number: 4]

This question is about polymers.

(a)

All types of nylon are condensation polymers.

[ 4 ]

(i)

State what is meant by the term condensation polymer.

[ 2 ]

An answer that makes reference to the following points:

- (polymer is a very) large molecule

OR (polymer is formed from) large number of / many monomers

(1)

- (condensation as) splitting off of a (small) molecule (1)

Allow long-chain (molecule) Allow macromolecule Allow repeating for many Ignore 2 or more / several / different for many Ignore (formed by) addition

Allow with loss/elimination of $\mathrm{H}_{2} \mathrm{O} / \mathrm{HCl}$ Ignore forms byproduct

Expert

(ii)

The structure of nylon 6,6 is shown.

nylon 6,6

Nylon 6,6 is made from two monomers.
Deduce the structural formulae of these two monomers.
structural formula of monomer 1
structural formula of monomer 2

[ 2 ]

An answer that makes reference to the following points:

- structure of hexanedioyl dichloride

- structure of hexane-1,6-diamine

Accept monomers in either order

Allow any combination of skeletal, structural or displayed formulae If more than one type of formula shown, all must be correct

Penalise errors in chain length once only

Ignore connectivity in structural formulae eg Allow $\mathrm{COClCH}_{2} \ldots / \mathrm{COOHCH}_{2} \ldots / \mathrm{NH}_{2} \mathrm{CH}_{2} \ldots$ eg Allow $\mathrm{C}=\mathrm{OCl}-\mathrm{CH}_{2} \ldots / \mathrm{C}=\mathrm{OOH}-\mathrm{CH}_{2} \ldots / \mathrm{NH}_{2}-\mathrm{CH}_{2} \ldots$

Penalise connectivity in skeletal / displayed formulae once only

Allow structure of hexanedioic acid

Examples of correct structures:

$\mathrm{ClOCCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COCl} / \mathrm{ClOC}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{COCl}$ $\mathrm{HOOCCH} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COOH} / \mathrm{HOOC}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{COOH}$

Expert

[Maximum number: 1]

This question is about benzene and some of its compounds.

Semi-aromatic polyamides have high melting temperatures, high strength and rigidity and are resistant to chemical attack so they have many applications in engineering.

Draw the repeat unit of the polyamide formed from the monomers shown.
$\mathrm{H}_{2} \mathrm{~N}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{NH}_{2}$ and

Figure for Question 12 — Edexcel A-Level Chemistry A2

[Maximum number: 2]

This question is about benzene and some of its compounds.

Semi-aromatic polyamides have high melting temperatures, high strength and rigidity and are resistant to chemical attack so they have many applications in engineering.

Explain why polyamides have higher melting temperatures than polyalkenes.

An answer that makes reference to the following point:

- because there is hydrogen bonding (and London forces between the chains) in a polyamide

- (and this is) stronger than the London forces between the chains in polyalkenes (so more energy is needed to separate the polyamide molecules) or the London forces between the chains in polyalkenes are weaker (than hydrogen bonding so more energy is needed to separate the polyamide molecules)

Reference to breaking of covalent bonds scores (0) Ignore references to (permanent) dipole forces

Allow 'it' for the polyamide since it is the subject of the question, so "it has hydrogen bonding" scores M1

Do not award if hydrogen bonding to water stated Do not award if hydrogen bonding shown by $\mathrm{CH}_{2}$ Do not award if ionic bonding or ions referred to

Accept dispersion forces / attractions between temporary and induced dipoles for London forces Allow van der Waals’ forces for London forces

Allow London forces in polyalkenes are easier to overcome (than hydrogen bonding)

Note that M2 is awarded for a comparison of the weakness of London forces to the strength of hydrogen bonding. Hence M2 is dependent on M1 or near-miss

COMMENT

Reference to polyalkenes "only having London forces" compared to polyamides having hydrogen bonding is not enough for M2 unless the hydrogen bonding is stated to be strong

Allow reference to molecules rather than chains