Here are a selection of examples for you to look at

Example 1: Show how bromomethane, CH₃CH₂Br can be converted into ethylethanoate, CH₃COOCH₂CH₃

Method

Identify which molecules can be made from bromomethane, then what molecules will give ethyl ethanoate.

The product, an ester can be made from ethanoic acid and ethanol. Reacting the bromoethane with sodium hydroxide would produce ethanol in an electrophilic substitution reaction. The ethanol could then be oxidised to produce ethanoic acid, which can be undergo esterification with ethanol to produce the desired product ethyl ethanoate.

A likely reaction sequence is:

Example 2: Show how CH₃CH=CH₂ can be converted into (CH₃)₂CHCH₂NH₂

Method

There is a double bond in the starting molecule but not in the product so an electrophilic addition reaction must be the first step. The -CH₂NH₂ section suggests the reduction of a nitrile (-C≡N) group as the final step. The product also has one more carbon so a nitrile must have been produced using a cyanide ion in a nucleophilic substitution step. The cyanide group is most likely to have been introduced by a nucleophile substitution of a haloalkane. This suggests the addition of HBr to the propene must be the first step.

A suggested reaction sequence is therefore:

Example 3 – A challenging one: Outline a reaction sequence for the synthesis of CH₃COCH₂NHCOCH₃, starting from ethanal, using appropriate reagents

Method

The product contains a ketone group and an N-substituted amide. So, working backwards:

• 1-aminopropanone → target molecule

• 1-aminopropan-2-ol → 1-aminopropanone

• 2-hydroxypropanenitrile →1-aminopropan-2-ol

• ethanal →2-hydroxypropanenitrile

The complete reaction sequence is therefore: 

ethanal →2-hydroxypropanenitrile →1-aminopropan-2-ol 1-aminopropanone → target molecule