Organic Synthesis (Cambridge (CIE) A Level Chemistry): Exam Questions

But-2-ene can be converted into butan-2-ol by two different synthetic routes. One route can be carried out as a one-step process whilst the other requires two steps.

State reagents and provide an equation, using structural formulae, for the one-step process.

Draw a reaction scheme, including reagents and conditions for the two step process.

But-1-ene can be used to form butan-2-ol by both the one-step and two-step reaction schemes. Explain why using but-1-ene gives a lower yield of butan-2-ol.

Give the displayed formula of the organic compound(s) formed when but-2-ene is

• reacted with cold, dilute MnO₄^– ions,

• reacted with hot, concentrated MnO₄^– ions

A series of reactions based on butan-1-ol is shown is Fig. 2.1.

Fig. 2.1

Suggest a suitable reagent and conditions for reaction 1.

i) Write an equation for reaction 2, using [O] to represent the oxidising agent.

[1]

ii) Suggest a suitable reagent and conditions for reaction 2.

[2]

Give the structural formulae of U and V.

U ............................................

V ............................................

Suggest a suitable reagent and conditions for reaction 3.

Some reactions of compound A are shown in Fig. 3.1.

Fig. 3.1

Draw the skeletal structures of compounds B, C and D

State the colour change when compound D is formed.

Compound A reacts with iodine and sodium hydroxide ions to give two products. Draw the skeletal structures of these two products.

State the name of compound A.

The reaction scheme shows three steps to synthesise 2-hydroxy-2-methylpropanenitrile.

Name the type of mechanism that occurs in

• reaction 1

• reaction 3

State the reagents and conditions required for 

• reaction 1

• reaction 2

Draw the mechanism that occurs in reaction 3

Explain why 2-hydroxy-2-methylpropanenitrile does not exhibit optical isomerism.

The following reaction pathway in Fig. 5.1 is used to produce compounds A and B, which when reacted together, form a branched ester molecule, compound C. 

Suggest suitable reagents and conditions for the synthesis of compound A via step 1 and give the name for this type of reaction.

Fig. 5.1

In order for the ester to be produced, the ketone in part (a) must be converted to another compound, B.

i) Name and draw the structure of the molecule that is produced from step 2.

[2]

ii) Give the name of the type of reaction that is involved in step 2 and suggest suitable reagents and conditions for the process.

[2]

Outline how ethanol can be synthesised from ethane in two steps. State the reaction conditions and reagents and name the type of reaction taking place.

The four step synthesis to form propan-1-ol from a ketone is outlined below in Fig. 5.2.

Fig. 5.2

i) Give the names of four possible substances A to D

[1]  

ii) Give the reagents and conditions for step 4.

[2]

This question is about a reaction pathway to produce 1-bromo-1-methylcylcohexane.

1-bromo-1-methylcyclohexane can be produced by the following reaction steps, as shown in Fig. 1.1 below.

Fig. 1.1

Name and outline the mechanism for the reaction between compound E and hydrogen bromide, HBr. In your answer, draw the major product of the reaction.

Explain why a major product and minor product are produced in the reaction outlined in part (a)

Suggest a possible starting molecule for the reaction pathway in part (a) and give the reagents required for step 1 based on this starting molecule.

This question is about reaction profiles using chloroalkanes

For the reaction profile outlined in Fig. 2.1, state the mechanism or type of reaction for each step.

1-chlorobutane      Compound G      Compound H

 Fig. 2.1

Step 2 is carried out by heating under reflux.

Identify Compound H.

1-chlorobutane can be produced from an alkene.  Identify the alkene and give the reagent required.

Explain how the functional group of the final compound in the reaction scheme in part (a) would be different if 2-chlorobutane was used as the starting compound.

Compounds W, X and Y are all compounds containing carbon, hydrogen and oxygen only. Compounds X and Y are straight chain compounds, each containing five carbons. Compound W and a byproduct, compound Z, are formed from the reaction between compound X and Y. Compound X can be oxidised by the reaction with acidified potassium dichromate to give compound Y.

2.754 g of compound Y contains 0.027 moles.

Using the information given, state the name of compound Y.

Deduce the structural formula of compound W and explain how compound Z is formed in the reaction.

Compound X will oxidise to compound Y if allowed to fully oxidise. Explain how a student could stop the full oxidation of compound X. 

Deduce the formula of an isomer of compound X that will not react with acidified potassium dichromate, H⁺ / K₂Cr₂O₇.