Amines (AQA A Level Chemistry)

Name the compound drawn in Figure 1 and state the class of compound to which it belongs.

Figure 1

The compound in Figure 1 in part (a) can be formed during the reaction of ethylamine, CH₃CH₂NH₂, and chloroethane, CH₃CH₂Cl.

Name and outline the mechanism for this reaction.

Explain why an excess of ethylamine, CH₃CH₂NH₂, is required for the formation of the compound in Figure 1 in part (a).

Triethylamine, (CH₃CH₂)₃N and the compound in Figure 1 of part (a) are two different types of amines.

i) Explain how you could differentiate between these two compounds using an IR spectrum.

ii) Triethylamine, (CH₃CH₂)₃N can also undergo a reaction with chloroethane. Draw and give a use for the product of this reaction.

Three nitrogen containing molecules, ammonia, NH₃, phenylamine, C₆H₅NH₂ and N-methylethylamine, CH₃CH₂NHCH₃, are drawn below respectively in Figure 1.

Figure 1

 i) List the three amine molecules drawn in Figure 1 in order of increasing base strength.

ii) Explain your answer to part (i).

Phenylamine, C₆H₅NH₂ shown in Figure 1 in part (a) can be produced from nitrobenzene, C₆H₅NO₂.

Name the type of reaction and suggest suitable reagents and conditions for this conversion.  

Azo dyes are organic compounds, which are largely used in the treatment of textiles andleather products, as well as in food. Phenylamine, C₆H₅NH₂, can be used in the manufacture of azo dyes.

The manufacturing process is outlined below.

Step 1

Phenylamine is dissolved in HCl to produce a diazonium salt. A diazonium salt contains two nitrogen atoms joined together by a triple bond. The reaction for this process is as follows:

C₆H₅NH₂  +  HCl   +  HNO₂   →    C₆H₅N₂⁺Cl^-    +   2H₂O

Step 2

This solution is then slowly added to an alkaline solution of a phenol coupling agent to form the dye.

i) The diazonium salt, C₆H₅N₂⁺Cl^-_, is an unstable compound. Suggest a condition that could be added to ensure that the salt would not break down during the reaction.

ii) Draw the structure of the diazonium salt formed in Step 1, showing the displayed formula of the nitrogen containing group.

Phenol, C₆H₅OH, is an aromatic organic compound which is also crucial in the manufacture of azo dyes.

The final step of the azo dye production, involves pairing up the diazonium salt with a phenol compound as a coupling agent.

Suggest a structure for the azo dye if the coupling agent used is 2,6-dimethylphenol.

Amines will react with acid chlorides to produce a different nitrogen containing product. 

i) Name and outline the mechanism between ethanoyl chloride, CH₃COCl and methylamine, CH₃NH₂.

ii) Give the IUPAC name of the compound formed in the reaction.

Name and draw the structure of the two compounds formed in the reaction of methylamine, CH₃NH₂ and propanoic anhydride.

Methylamine, CH₃NH₂ also reacts with ethanoic anhydride, CH₃COOCOCH₃ in a less vigorous reaction. Suggest why using an acid anhydride such as ethanoic anhydride is more favourable than using ethanoyl chloride.

i) Two separate solutions of methylamine, CH₃NH₂ and dimethylamine, (CH₃)₂NH, were left unlabelled in a laboratory. Suggest how, other than smell, they could be distinguished from one another.

ii) Give an explanation to your answer to part (i).

Figure 1 shows a reaction scheme in which Compound A undergoes three different reactions to produce three different products. 

Figure 1

Explain how the reactions and the conditions of Reaction 2 and Reaction 3 are different from one another.

Compound B drawn in Figure 1 of part (a) is a primary amine. 

Give the IUPAC name of Compound B and outline a mechanism for Reaction 1, stating a condition which would reduce contamination of the primary amine.

Draw a branched chain optical isomer of Compound B from Figure 1 that would display optical isomerism.

An alternative method of producing Compound B in Figure 1 part (a) is from 1-bromopropane, CH₃CH₂CH₂Br in two steps.

i) State the reagents and conditions required for both steps of this reaction and give the name of the intermediate compound formed.

ii) Suggest one advantage and one disadvantage for this method.

The compound drawn in Figure 1 below is caffeine. Caffeine is a stimulant drug that speeds up the messages travelling between the brain and body. Ingesting too much caffeine may promote headaches and high blood pressure.

Figure 1

i) Give the molecular formula of caffeine.

ii) Calculate the percentage by mass of nitrogen in caffeine. Give your answer to 1 decimal

Deduce the total number of peaks in the ¹³C NMR spectrum of caffeine.

i) Which functional group is not present in a molecule of caffeine drawn in Figure 1 part (a)?

A         Alkene 

B         Ketone 

C         Amine 

D         Amide

ii) Give the name, including the classification, of the functional group that contains the Nitrogen atom labelled c.

Suggest why the nitrogen atoms labelled a and b are unlikely to be protonated. 

Compounds A, B, C and D shown in Figure 1 are all nitrogen compounds. State the IUPAC names for compounds A and B.

Figure 1

State which amine is more basic, compound C or D. Explain your answer.

Explain why 2-chloropyridine shown in Figure 2 is less basic than pyridine.

Figure 2

Outline the mechanism for the formation of compound B using the required acyl chloride. 

Phenylamine is a weak base and can be prepared from benzene in two steps. State the reagents and conditions required for the preparation of phenylamine from benzene.

Write an equation to show how the free amine is liberated from the salt formed in the second step using sodium hydroxide. 

Explain why phenylamine can not be prepared from chlorobenzene via reaction with ammonia under normal conditions.

Explain why phenylamine is insoluble in water.

2-bromopropane can undergo a two step process to form a primary amine containing four carbon atoms.

i) State the name of the primary amine produced after both steps.

ii) Give the reagents and conditions required to form the intermediate compound in step one.

In step two the amine is produced from the intermediate formed in step 1.

i) Draw the structure for the intermediate formed in step one.

ii) State the reagents and conditions required for step two.

iii) Write an equation for the reaction that occurs in step two. 

If excess 2-bromopropane is used in part (a), further substitution will occur. Outline the mechanism for the formation of the tertiary amine from a secondary amine for the reaction between excess 2-bromopropane and propylamine. 

A solid product is produced in the reaction in part (c). Draw the structure of the solid produced in this reaction.

Compound X is produced from cyclohexene. An amine which is a relatively weak base containing one nitrogen atom can be produced from Compound X in one step.

Outline a mechanism for the formation of Compound X from cyclohexene. You will need to give suitable reagents in your answer.

State the reagents and conditions for the conversion of Compound X into the amine molecule. 

Figure 1 shows three amine compounds, Compounds E, F and G.

Figure 1

List the amines in order of increasing basicity. Justify your answer.

Write an equation to show how propylamine will react when mixed with water.

Methyl orange is an azo dye which exists in two forms depending on the pH. 

Figure 1

Suggest a structure for the diazonium salt that is used to form methyl orange which has the formula C₆H₄(SO₃Na)NH₂.

Ethylamine will react with propanoic anhydride to produce two compounds, draw the compounds produced in this reaction. 

A reaction scheme for the production of a secondary amine, Compound Z, is given in the following sequence shown in Figure 2.

Figure 2

i) Give the reagents and conditions required for Step 1.

ii) Give the IUPAC name for compound Y.

The amine produced, compound Z, is a secondary amine.

i) Propylamine is reacted with chloromethane to produce compound Z. Draw a possible structure for compound Z.

ii) Give one advantage of forming an amine through this method.

iii) Compound Z is reacted with excess chloromethane. Draw the solid product formed from this reaction.