7.9 Organic Mechanisms (A Level only)

The preparation of a common ‘over the counter drug’ is outlined in Figure 1. This reaction occurs in the presence of a few drops of concentrated sulfuric acid.

Figure 1

Give the IUPAC names of Compounds A and B

Using Figure 1 in part (a), suggest a mechanism for the formation of Compound C.

Suggest why ethanoic anhydride is used in the preparation of Compound C instead of ethanoyl chloride.

Draw the structure of the product from the reaction between Compound A and methanol in the presence of a few drops of concentrated sulfuric acid.

Figure 1 shows the formation of a ketone via electrophilic substitution. Outline the mechanism to show the formation of the catalyst and electrophile responsible for this reaction.

Figure 1

Outline the mechanism for the formation of the ketone, including the regeneration of the catalyst required.

Outline the mechanism for the conversion of Compound X to Compound Y if sodium tetrahydridoborate, NaBH₄, is used as the reducing agent.

           
Figure 1

Name the product of the reaction between Compound Z and lithium aluminium hydride LiAlH₄. 

The reversible reaction for the formation of an ester is shown in Figure 1.

Figure 1

An example of an ester is propyl ethanoate. State the type of mechanism that occurs when this ester is hydrolysed in alkaline conditions.

Using propyl ethanoate as an example, outline the mechanism for the hydrolysis reaction that takes place in alkaline conditions.

Please note you do not need to show the deprotonation step.

An ester can be formed from one molecule. Figure 1 shows the formation of a cyclic ester from 5-hydroxypentanoic acid. Step one of the mechanism is the protonation of the oxygen atom in the C=O and step two is the cyclisation of the molecule.

Suggest a mechanism to show these two steps.

Figure 1

The final step to this mechanism is deprotonation of the molecule. Using Figure 2, suggest a mechanism for the formation of intermediate C from B.

Figure 2

Name the amine which has the formula (CH₃CH₂)₂NH

Outline the mechanism to show the reaction between (CH₃CH₂)₂NH reacts with a small excess of chloromethane, CH₃C.

Draw and name the product of the reaction between a large excess of chloromethane and (CH₃CH₂)₂NH.

Write two equations to show the reaction of CH₃CH₂NH₂ and ethanoic anhydride. 

This question is about the reactions of carbonyl compounds.

Pentan-2-one is reduced using sodium borohydride, NaBH₄, followed by dilute hydrochloric acid in a two-step reaction.

Write an equation to show the reaction which takes place during the reduction of pentan-2-one and give the IUPAC name of the product formed.

[H] should be used to represent NABH₄ in the equation.

In the reaction between pentan-2-one and NaBH₄ a hydride ion is involved.

Give the formula of a hydride ion and suggest its role in the reaction.

Outline the mechanism between pentan-2-one and NaBH₄.

The product formed in part (c) is optically inactive. Explain why.

Acylation reactions are used in many industries including pharmaceuticals and textiles.            

Figure 1

Although acid anhydrides have a slower rate of reaction than acyl chlorides they generally make better acylation agents than acyl chlorides.

Give 3 reasons why.

Ethanoyl chloride and propylamine react together to produce a primary amide.

Butan-2-ol also undergoes a nucleophilic addition-elimination reaction with ethanoyl chloride.

Outline the mechanism for the reaction

Tetrabutylammonium chloride (Figure 1) is an example of a cationic surfactant with many uses, including a type of chromatography known as ion-pair chromatography.

Name this type of compound and give the skeletal formula of the compound shown in Figure 1.

Figure 1

Tetrabutylammonium chloride is made by a reaction involving a halogenoalkane.

State the reaction conditions and name the type of mechanism involved in this reaction.

Propylamine is a colourless liquid with a fishy ammonia-like odour. Its main use is in chemical manufacture.

Outline a mechanism for the reaction of ammonia with 1-chloropropane, to form propylamine, CH₃CH₂CH₂NH₂.

Ethylamine can react with bromoethane to produce a compound with a molecular formula of C₄H₁₁N.

Outline the mechanism for the reaction and name the organic product which is formed.

This question is about the reactions of aromatic compounds.

Explosives and dyes are produced by a reaction which involves nitrating a benzene ring.

Give the mechanism for the reaction between benzene and the nitronium ion to produce nitrobenzene.

Benzene is a useful in the production of pharmaceuticals, however due to the stability of the benzene ring it is fairly unreactive with electrophiles. Instead stronger electrophiles can be made by using a halogen carrier such as aluminium chloride, AlCl₃ with ethanoyl chloride.

Phenylamine reacts with bromoethane to produce a secondary amine, N-ethyl-N-phenylamine.

Outline the mechanism for the reaction and suggest how the conditions can be controlled to reduce further substitution on the amine.