Planning Reaction Schemes | Edexcel International A Level Chemistry Revision Notes 2017

Reaction Schemes

A large number of organic products are made from a few starting compounds using appropriate reagents and conditions
Knowing how organic functional groups are related to each other is key to the synthesis of a given molecule
The main functional groups you need to know are
- Alkanes
- Alkenes
- Haloalkanes
- Nitriles
- Amines
- Alcohols
- Carbonyls (aldehydes & ketones)
- Hydroxynitriles
- Carboxylic acids
- Esters
- Acyl chlorides
- Primary and secondary amides

Aliphatic Reactions Table

Reactant	Product	Reagents	Reaction
Alkene	Haloalkane	X₂ / HX	Electrophilic addition
Alkene	Alcohol	Steam + H₂SO₄/ heat	Hydration
Alkene	Alkane	Hydrogen + Ni catalyst / 150 ^oC	Electrophilic addition / hydrogenation
Alcohol	Alkene	Al₂O₃ or conc. H₂SO₄/ heat	Elimination / dehydration
Alcohol	Haloalkane	NaX + H₂SO₄/ reflux	Nucleophilic substitution
Haloalkane	Alcohol	NaOH (aq) / reflux	Nucleophilic substitution
Alkane	Haloalkane	Halogen / UV light	Free radical substitution
Primary alcohol	Aldehyde	K₂Cr₂O₇ / H₂SO₄/ distil	Oxidation
Secondary alcohol	Ketone	K₂Cr₂O₇ / H₂SO₄/ Heat	Oxidation
Primary alcohol	Carboxylic acid	K₂Cr₂O₇ / H₂SO₄/ reflux	Oxidation
Aldehyde	Primary alcohol	NaBH₄ / H₂O	Reduction / nucleophilic addition
Ketone	Secondary alcohol	NaBH₄ / H₂O	Reduction / nucleophilic addition
Haloalkane	Nitrile	Aqueous ethanolic KCN / Heat	Nucleophilic substitution
Halogenoalkane	Amine	NH₃ / ethanol	Nucleophilic substitution
Nitrile	Carboxylic acid	H₂O / HCl	Hydrolysis
Aldehyde	Hydroxynitrile	NaCN / H⁺	Nuclophilic addition
Alcohol	Ester	Carboxylic acid / H₂SO₄	Esterification
Carboxylic acid	Ester	Alcohol / H₂SO₄	Esterification
Ester	Carboxylate salt and alcohol	NaOH (aq)	Alkaline hydrolysis
Ester	Carboxylic acid	Dilute acid	Acid hydrolysis
Carboxylic acid	Acyl chloride	SOCl₂	Chlorination
Acyl chloride	Carboxylic acid	H₂O	Hydrolysis
Acyl chloride	Primary amide	NH₃	Nucleophilic addition elimination
Acyl chloride	Secondary amide	Primary amine	Nucleophilic addition elimination

Aromatic Reactions Table

Reactant	Product	Reagents	Reaction
Benzene	Methylbenzene / toluene	CH₃Cl / AlCl₃	Alkylation / Electrophilic substitution
Benzene	Bromobenzene	Br₂ / FeBr₃	Bromination / Electrophilic substitution
Benzene	Chlorobenzene	Cl₂ / AlCl₃	Chlorination / Electrophilic substitution
Benzene	Nitrobenzene	HNO₃ / H₂SO₄	Nitration / Electrophilic substitution
Nitrobenzene	Aminobenzene / phenylamine / aniline	Sn / HCl	Reduction
Aminobenzene	2,4,6-tribromoaminobenzene / 2,4,6-tribromoaniline	Bromine	Electrophilic substitution
Benzene	Phenylethanone	CH₃COCl / AlCl₃	Acylation / Electrophilic substitution
Phenylethanone	1-phenylethanol	NaBH₄	Reduction

The given molecule is usually called the target molecule and chemists try to design a synthesis as efficiently as possible
Designing a reaction pathway starts by drawing the structures of the target molecule and the starting molecule
Determine if they have the same number of carbon atoms
- If you need to lengthen the carbon chain you will need to put on a nitrile group by nucleophilic substitution
Work out all the compounds that can be made from the starting molecule and all the molecules that can be made into the target molecule
- Match the groups they have in common and work out the reagents and conditions needed

Suggest how the following syntheses could be carried out:

a) Chloroethane to ethanoic acid

b) Ethene to 1-aminopropane

Answer 1

Organic synthesis WE Answer 1, downloadable AS & A Level Chemistry revision notes

Answer 2

Organic synthesis WE Answer 2, downloadable AS & A Level Chemistry revision notes

You could be required to design a synthesis with up to four steps

Part of this process can include identifying appropriate control measures to reduce risk, based on data about hazards