AQA A-Level Chemistry Organic Mechanisms

Name and outline the mechanism, reagents and conditions, for the reaction of an alkane to a haloalkane.

[Free-radical substitution]

E.G.

1. Initiation, essential: UV light

Cl₂ --> 2Cl•

2. Propagation

CH₃CH₃ + Cl• --> HCl + CH₃CH₂•

CH₃CH₂• + Cl₂ --> CH₃CH₂Cl + Cl•

3. Termination

CH₃CH₂• + Cl• --> CH₃CH₂Cl

Name and outline the mechanism, reagents and conditions, for the reaction of a haloalkane to an alkene.

[Elimination]

NaOH, ethanol, reflux

Name and outline the mechanism, reagents and conditions, for the reaction of a haloalkane to an alcohol.

[Nucleophilic substitution]

Warm NaOH(aq), reflux

Name and outline the mechanism, reagents and conditions, for the reaction of an alkene to a haloalkane.

[Electrophilic addition]

HBr, 20°C

Name and outline the mechanism, reagents and conditions, for the reaction of an alkene to an alcohol. (1) (H+)

i.e. Hydration of an alkene

[Acid catalysed addition]

H₃PO₄ catalyst, steam, 300°C, 60atm

Name and outline the mechanism, reagents and conditions, for the reaction of an alkene to an alcohol. (2) (H2SO4)

[Electrophilic addition]

H₂O, H₂SO₄ catalyst

Name and outline the mechanism, reagents and conditions, for the reaction of an alcohol to an alkene.

[Acid-catalysed elimination]

Conc. H₂SO₄ or H₃PO₄, reflux

Name and outline the mechanism, reagents and conditions, for the reaction of an alkene to a dribomoalkane.

[Electrophilic addition]

Br₂, 20°C

Name and outline the mechanism, reagents and conditions, for the reaction of a haloalkane to a nitrile.

[Nucleophilic substitution]

KCN(aq) in ethanol, reflux

Name the reaction, reagents and conditions for the conversion of a nitrile to a primary amine.

Reduction - LiAlH₄ in ether, dilute H₂SO₄

OR

Hydrogenation - H₂, Ni catalyst

Name and outline the mechanism, reagents and conditions, for the reaction of a haloalkane to a primary amine.

[Nucleophilic substitution]

Excess NH₃, heat

Product = Ethylamine

Name the mechanism, reagents and conditions, for the reaction of a haloalkane to a secondary amine.

[Nucleophilic substitution]

Primary amine (e.g. CH₃CH₂NH₂), heat

Name the mechanism, reagents and conditions, for the reaction of a haloalkane to a tertiary amine.

[Nucleophilic substitution]

Secondary amine (e.g. CH₃CH₂NHCH₂CH₃), heat

Name the mechanism, reagents and conditions, for the reaction of a haloalkane to a quaternary ammonium ion.

[Nucleophilic substitution]

Tertiary amine (e.g. CH₃CH₂N(CH₂CH₃)CH₂CH₃), heat

Produces an ammonium ion

Name the reaction, reagents and conditions, for the conversion of an alcohol to an aldehyde/ketone.

Oxidation - K₂Cr₂O₇, H₂SO₄ ( i.e. K₂Cr₂O₇/H⁺) heat in distillation apparatus

Primary alcohol --> aldehyde

Secondary alcohol --> ketone

Name and outline the mechanism, reagents and conditions, for the reaction of an aldehyde/ketone to an alcohol.

[Nucleophilic addition]

NaBH₄ in aqueous solution with methanol

Aldehydes produce primary alcohols.

Ketones produce secondary alcohols.

Name and outline the mechanism, reagents and conditions, for the reaction of an aldehyde/ketone to a hydroxynitrile.

[Nucleophilic addition]

KCN(aq) or HCN(aq), H₂SO₄, 20°C

Product = 2-methylpropanenitrile (from a ketone)

Name the reaction, reagents and conditions, for the conversion of an aldehyde to a carboxylic acid.

Oxidation - K₂Cr₂O₇, H₂SO₄ ( i.e. K₂Cr₂O₇/H⁺) reflux

Name and outline the mechanism, reagents and conditions, for the reaction of an acyl chloride to a primary amide.

[Nucleophilic addition-elimination]

NH₃, 20°C

Product = Ethanamide

Name and outline the mechanism, reagents and conditions, for the reaction of an acyl chloride to a N-substituted amide.

[Nucleophilic addition-elimination]

Amine, 20°C

Product = N-ethylethanamide

Name and outline the mechanism, reagents and conditions, for the reaction of an acyl chloride to an ester.

[Nucleophilic addition-elimination]

Alcohol, 20°C

Product = Ethylethanoate

Name and outline the mechanism, reagents and conditions, for the reaction of an acyl chloride to a carboxylic acid.

[Nucleophilic addition-elimination]

H₂O, 20°C

Name the reaction, reagents and conditions, for the conversion of a carboxylic acid to an ester.

Esterification - Alcohol, conc. H₂SO₄ catalyst, heat

Name the reagents and conditions for the reaction of an ester to a carboxylic acid.

Dilute H₂SO₄ catalyst, H₂O, reflux

OR

Dilute NaOH(aq), reflux

For the reaction of benzene to a phenylketone,

(i) write an equation for the formation of the reactive species

(ii) Name and outline the mechanism, reagents and conditions

(i) Formation of electrophile:

CH₃COCl + AlCl₃ --> CH₃CO⁺ + AlCl₄⁻

(RCOCl + AlCl₃ --> RCO⁺ + AlCl₄⁻)

Electrophile = CH₃CO⁺ (RCO⁺)

(ii) Electrophilic substitution

CH₃COCl (RCOCl), AlCl₃ catalyst, non-aqueous environment

Product = 1-phenylethanone / methyl phenyl ketone

For the reaction of benzene to nitrobenzene,

(i) write an equation for the formation of the reactive species

(ii) Name and outline the mechanism, reagents and conditions

(i) Formation of electrophile:

HNO₃ + 2H₂SO₄ --> NO₂⁺ + 2HSO₄⁻ + H₃O⁺

Electrophile = NO₂⁺

(ii) Electrophilic substitution

Conc. H₂SO₄, conc. HNO₃, below 55°C

For the conversion of nitrobenzene to phenylamine,

(i) Name the reaction, reagents and conditions

(ii) Write an equation for this reaction, using [H] to represent the appropriate agent.

(i) Reduction - Sn, conc. HCL, reflux, NaOH(aq)

(ii) [H] to represent the reducing agent.

C₆H₅NO₂ + 6[H] --> C₆H₅NH₂ +2H₂O

Name and outline the mechanism, reagents and conditions, for the reaction of phenylamine to a N-phenylethanamide.

[Nucleophilic addition-elimination]

CH₃COCl