CH4 - Amines - Flashcards in A Level and IB Chemistry

All amines have the group...

NH2

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Primary aliphatic amines can be formed in 2 different ways. What are these two reactions?

1. Nucleophilic substitution with halogenoalkanes. 2. Reduction of nitriles

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Nuclephilic substitution of halogenoalkanes - conditions?

Ammonia, sealed tube, 100'C, aqueous OR alcoholic conditions.

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Nuclephilic substitution of halogenoalkanes - what occurs first?

The halogenoalkane will react with the ammonia to form an ammonium salt.

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What happens next?

The ammonium salt will react with excess ammonia to form an aliphatic amine and an ammonium halide (e.g. chloride, NH4+Cl-)

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Why is the reaction between a halogenoalkane and ammonia described as nucleophilic substitution?

The carbon-halogen bond is polarised. The carbon atom attracts a lone pair of electrons from the +NH3.

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The reduction of nitriles - conditions?

Lithium aluminium hydride dissolved in ethoxyethane.

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When writing the equation for the reduction of nitriles, what number goes in front of the [H]?

4[H]

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How could you separate an amine from a nitrile?

An amine acts as a base - it could be treated with dilute acid to form an ammonium salt. This would cause an organic and aqueous layer to form. This can then be separated.

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Formation of aromatic amines from nitrobenzenes - conditions?

Tin and concentrated HCl.

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When writing the equation for the formation of aromatic amines from nitrobenzenes, what number goes in front of the [H]?

6[H]

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Explain the basicity of aliphatic amines.

The nitrogen atom has a lone pair of electrons. The alkyl groups 'push' electrons slightly towards the nitrogen atom, making it more ∂-. Therefore, the lone pair on the nitrogen is enriched, attracting protons more strongly.

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Explain the basicity of aromatic amines.

The nitrogen atom has a lone pair of electrons. The nitrogen lone pair can delocalise and become part of the delocalised pi e- system, making the nitrogen relatively less ∂-. However, this makes phenyl amine more susceptible to electrophilic sub.

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Which is the strongest base - ammonia, an aliphatic amine or an aromatic amine?

STRONGEST = aliphatic amine. WEAKEST = aromatic amine.

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Ethanoylation of primary amines - conditions?

Ethanoyl chloride and room temperature.

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Primary amines and cold nitric acid - conditions?

Cold nitric acid and temperature < 10'C

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Aromatic amines and nitric acid - what happens if the temperature above 10'C?

The benzenediazonium ion will decompose to form an alcohol and evolve N2, similar to that with aliphatic amines.

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Aromatic amines and nitric acid - what happens if the temperature is below 10'C?

The benzenediazonium ion is produced.

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A diazonium salt reacts with another compound containing a...

benzene ring called a coupling agent.

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What is an azo bridge?

N=N

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Coupling reactions - conditions?

Temperature < 10'C and alkaline solution (NaOH).

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Difference between an amine and an amide?

An amide has a C=O group alongside its NH2.

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Define a base.

An electron pair donor/proton acceptor.

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Define an acid.

An electron pair acceptor/proton donor.

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CH4 - Amines

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