Amines

The reaction between methylamine (CH₃NH₂) and excess bromoethane (C₂H₅Br) produces a quaternary ammonium salt.

What is the formula for the cation in this salt?

Which compound can be used as a cationic surfactant?

This question is about amines.

CH₃CHBrCH₂CH₃ reacts with NH₃

Draw the skeletal formula of the major organic product formed when

• an excess of NH₃ is used

• an excess of CH₃CHBrCH₂CH₃ is used.

Product with excess NH₃

Product with excess CH₃CHBrCH₂CH₃

Figure 3 shows a two-step synthesis to make amine G.

Complete Figure 3 by drawing the mechanism for Step 1 and the displayed formula of amine G.

Figure 4 shows two amines, P and Q.

Explain why P is a stronger base than Q.

Figure 5 shows enthalpy of hydrogenation data for cyclohexene and benzene.

It also shows predicted data for the theoretical molecule cyclohexa-1,3,5-triene.

Compare benzene and the theoretical molecule cyclohexa-1,3,5-triene in terms of:

• stability

• shape

• carbon–carbon bond lengths.

For each of these properties, suggest reasons for any differences.

Use data from Figure 5 in your answer.

Two steps in the synthesis of an aromatic amine are shown.

State the two reagents needed for Step 1.

Give an equation to show the formation of the reactive intermediate from these two reagents.

Equation

State the reagent(s) needed for Step 2.

State a possible use for the amine formed in Step 2.

Acrylonitrile, H₂C=CHCN, can be used as a starting material for the synthesis of butane-1,4-diamine, as shown in this reaction scheme.

Use IUPAC rules to name isomer W.

Reaction 1 produces a mixture of W and two other isomers.

Draw the structures of the two other isomers.

Explain, by considering the mechanism of this reaction, why all three isomers are formed.

The reaction scheme is repeated here.

Identify the reagent that is warmed with isomer W in reaction 2.

State the other reaction condition needed.

State the reagent and reaction conditions needed for reaction 3.

Give an equation for reaction 3.

Reagent and conditions

Equation

An incomplete equation for the formation of nylon 4,6 from five molecules of butane-1,4-diamine and five molecules of hexanedioic acid is shown.

Deduce the values of x and y in this equation.

Figure 6 shows a section of the nylon 4,6 polymer molecule.

Figure 6

Draw, on Figure 6, another section of nylon 4,6 polymer showing two hydrogen bonds between the two sections.

Which compound is the strongest base?

This question is about the reaction scheme shown.

State the reagents needed for step 1 and the reagents needed for step 2.

Give the name of the mechanism for the reaction in step 3.

Name the reagent for step 4.

State a necessary condition for step 4.

Amine A is formed in step 2 and amine B is formed in step 5.

Explain why the yield of B in step 5 is less than the yield of A in step 2.

Explain why amine B is a stronger base than amine A.

A two-step preparation of propylamine is shown.

bromoethane → X → propylamine

What is X ?

Methylamine reacts with bromoethane by nucleophilic substitution to produce a mixture of products.

Which is not a possible product of this reaction?

This question is about 2-bromopropane.

Define the term electronegativity.

Explain the polarity of the C–Br bond in 2-bromopropane.

Electronegativity

Draw the skeletal formula of the main organic species formed in the reaction between a large excess of 2-bromopropane and ammonia.

Give a use for the organic product.

Skeletal formula

This question is about amines.

Give an equation for the preparation of 1,6-diaminohexane by the reaction of 1,6-dibromohexane with an excess of ammonia.

Complete the mechanism for the reaction of ammonia with 6-bromohexylamine to form 1,6-diaminohexane.

Suggest the structure of a cyclic secondary amine that can be formed as a by-product in this reaction.

Mechanism

Cyclic secondary amine

1,6-Diaminohexane can also be formed in a two-stage synthesis starting from 1,4-dibromobutane. Suggest the reagent and a condition for each stage in this alternative synthesis.

Stage 1 reagent and condition

Stage 2 reagent and condition

Explain why 3-aminopentane is a stronger base than ammonia.

Justify the statement that there are no chiral centres in 3-aminopentane.

Paracetamol is a medicine commonly used to relieve mild pain. Traditionally, paracetamol has been made industrially in a three-step synthesis from

Name the mechanism of the reaction in Step 1.

Complete the equation for the reaction in Step 2.

In theory, either ethanoyl chloride or ethanoic anhydride could be used in Step 3.

Complete the mechanism for the reaction of 4-aminophenol with ethanoyl chloride. RNH₂ is used to represent 4-aminophenol in this mechanism.

In practice, ethanoic anhydride is used in the industrial synthesis rather than ethanoyl chloride.

Give one reason why ethanoyl chloride is not used in the industrial synthesis.

In Step 3 other aromatic products are formed as well as paracetamol.

Draw the structure of one of these other aromatic products.

Chemists have recently developed a two-step process to produce paracetamol from phenol. In the first step, phenol is oxidised to hydroquinone.

In the second step, hydroquinone reacts with ammonium ethanoate to form paracetamol.

Complete the equation for this second step.

Calculate the mass, in kg, of hydroquinone (M_r = 110.0) needed to produce 250 kg of paracetamol.

Methylamine reacts with bromoethane by substitution to produce a mixture of products.

Which compound is not a possible product of this reaction?

Aqueous solutions of ammonia, ethylamine and phenylamine are prepared. Each solution has the same concentration.

Which is the correct order for the pH values of these solutions?

Which indicator should be used in a titration to find the concentration of a solution of methylamine using 0.010 mol dm^–3 hydrochloric acid?

Figure 1 shows some compounds made from a halogenoalkane.

Draw the displayed formula of compound J.

Name the mechanism for Reaction 2 and give an essential condition used to ensure that CH₃CH₂CH₂NH₂ is the major product.

Name of mechanism

Calculate the mass, in grams, of CH₃CH₂CH₂NH₂ produced from 25.2 g of CH₃CH₂CH₂Br in Reaction 2 assuming a 75.0% yield.

Give your answer to the appropriate number of significant figures.

When Reaction 2 is carried out under different conditions, a compound with molecular formula C₉H₂₁N is produced. Draw the skeletal formula of the compound. Identify the functional group in the compound including its classification.

Skeletal formula

Identify the reagent and conditions used in Reaction 3.

Name and outline a mechanism for Reaction 3.

Name of mechanism

Mechanism

Amines E, F and G are weak bases.

Explain the difference in base strength of the three amines and give the order of increasing base strength.

Amine F can be prepared in a three-step synthesis starting from methylbenzene.

Suggest the structures of the two intermediate compounds.

For each step, give reagents and conditions only. Equations and mechanisms are not required.