Organic Synthesis (AL) (CIE A Level Chemistry)

Ibuprofen and paracetamol are pain-relief drugs.

Fig. 1.1

Ibuprofen and paracetamol both contain the aryl (benzene) functional group.

Name the other functional groups present in each molecule.

ibuprofen .........................................................................

paracetamol ...................................................................

Ibuprofen contains a chiral centre and has two enantiomers.

   similarity.......................................

   difference.....................................

[1]

[1]

Paracetamol reacts separately with the two reagents shown in the table.

Complete Table 1.1 by:
• drawing the structures of the organic products formed,
• stating the types of reaction.

Table 1.1

One of the steps in the manufacture of ibuprofen is shown in Fig. 1.2.

[1]

[3]

[1]

Cuminyl alcohol can be synthesised from benzene by the following route shown in Fig. 2.1.

Fig. 2.1

Suggest reagents and conditions for steps 1–4.

Name the mechanism of step 2 and state the type of reaction in step 4.

Mechanism of step 2 ..........................................................................................................

Type of reaction in step 4 ....................................................................................................

Draw the reaction mechanism for step 2.

Deduce the number of peaks that would be present in the ¹³C NMR spectrum of cuminyl alcohol.

Outline how ethanal can be synthesised from ethane in three steps.

State the reaction conditions and reagents and name the type of reaction taking place.

The following reaction pathway in Fig. 3.1 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. 3.1

The ketone in part (a), must be converted to compound B to produce the ester.

Draw the skeletal formula of the ester formed from the reaction scheme.

Noradrenaline shown in Fig. 4.1 is a hormone and neurotransmitter, which is released during stress to stimulate the heart and increase blood pressure.

Fig. 4.1

State the names of three functional groups in the noradrenaline molecule.

Consider the following two step synthesis of noradrenaline from dihydroxybenzaldehyde in Fig. 4.2. 

Draw the structure of the intermediate Z in the box.

Suggest reagents for steps 1 and 2.

step 1 ..................................................................................................................................

step 2 ..................................................................................................................................

Dihydroxybenzaldehyde reacts with Br₂ (aq).

• Describe what you would see during this reaction
• Draw the structure of the product

Compound G is a naturally occurring aromatic compound that is present in raspberries.

Identify the functional groups present in compound G.

Complete Table 5.1 with information about the reactions of the three stated reagents with compound G.

Table 5.1

The dye H can be made from compound G by the route shown below in Fig. 5.1.

Fig. 5.1

[2]

[3]

Explain why dye H is very stable.

Benzocaine is an ester based compound that is used medicinally as a local anaesthetic in pain relievers and cough drops. One of the first industrial processes to manufacture benzocaine was the five-step reaction shown in Fig. 1.1.

Fig. 1.1

Give the systematic name of benzocaine.

Step 1 involves the reaction of benzene with bromomethane.

Concentrated sulphuric acid and concentrated nitric acid are used to form the ion required for step 2.

The following equilibrium is the first step in the formation of the ion:

H₂SO₄ + HNO₃ ⇋ HSO₄^– + H₂NO₃⁺

Suggest reagents and conditions for steps 3 - 5 of the synthesis.

   step 3 ................................................................................

   step 4 ................................................................................

   step 5 ................................................................................

Fig. 1.2 shows an alternative reaction scheme for the production of benzocaine.

Fig. 1.2

Propanone can be synthesised from 2-bromopropane according to the reaction scheme shown in Fig. 2.1.

Fig. 2.1

Step 1 is not completed in acidic conditions.

Suggest one reaction, including reagents and conditions, to replace steps 1 and 2.

Using structural formulae, write an equation for the reaction of compound B with an oxidising agent, [O], to form propanone.

Ethene is used in the radical-free synthesis of 1-aminopropane as shown.

ethene compound A  compound B  propylamine

Identify which step of the reaction scheme could use hydrogen cyanide. Explain your answer.

Draw the skeletal structure of compound A and state the reagents required for its formation.

The final step of the reaction scheme forms 1-aminopropane from compound B.

Name compound B and identify the type of reaction that compound B undergoes to form propylamine. Explain your answer.

Sudan II is an azo dye that was used as a colourant in chilli powder until it was banned due to its links to an increased risk of cancer.  It can be synthesised from 1,3-dimethylbenzene by the route shown in Fig. 4.1

Fig. 4.1

Draw the structures of the organic compounds A, B, C and D in the boxes.

Two other structural isomers of compound A could have been formed from the mononitration of 1,3-dimethylbenzene, as shown in Fig.4.2.

Fig. 4.2

Suggest, with the aid of suitable diagrams, why 1,3-dimethyl-2-nitrobenzene is likely to be the more abundant product.