Nitrogen Compounds (OCR A Level Chemistry A): Exam Questions

Name the compound drawn below and state the class of compound to which it belongs. 

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

Three nitrogen containing molecules NH₃, C₆H₅NH₂ and N-methylethylamine, CH₃CH₂NHCH₃, are drawn below:

i) State the IUPAC name of CH₃CH₂NHCH₃.

ii) Explain how these compounds can behave as a Brønsted-Lowry base. 

Phenylamine, C₆H₅NH₂ shown in part (c) can be produced from nitrobenzene, C₆H₅NO₂. 

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

Two amino acids, alanine and valine are drawn below.

i) Give the IUPAC name for valine.

ii) Draw the species formed when alanine is in a solution of high pH.

Name the type of reaction and the structural formula of alanine when it reacts with propanol, CH₃CH₂CH₂OH in the presence of concentrated sulfuric acid, H₂SO₄. 

The isoelectric point of alanine is at pH 6.0.

i) What is meant by the term isoelectric point

ii) Draw the structure of alanine at pH 6.0

Valine exists as a pair of stereoisomers.

Explain the meaning of the term stereoisomers and explain how the stereoisomers of valine can be distinguished from one another. 

The compound drawn 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.

i) Give the molecular formula of caffeine. 

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

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

There are three nitrogen atoms labelled in the caffeine molecule drawn in part (a)

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

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

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. Justify your answer.

Ethanoyl chloride, CH₃COCl and methylamine, CH₃NH₂ react to form an N-substituted amide. Name and draw the structure of the amide that is formed.

4-methylphenylamine is a useful compound in the manufacture of azo dyes. It can be manufactured from methylbenzene in two stages.

i) Draw the structure of the intermediate required to manufacture 4-methylphenylamine

ii) State the reagents and conditions required to manufacture the intermediate 

The final stage for the preparation of 4-methylphenylamine involves the intermediate being heated under reflux in the presence of concentrated hydrochloric acid and a tin catalyst. Explain why sodium hydroxide is also required in this step.

The reaction scheme below shows some reactions of Compound A to produce three different products. 

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

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

Give the IUPAC name of Compound B and state the conditions required for reaction 1. 

Draw an isomer of Compound B from part (a) that would display optical isomerism.

An alternative method of producing Compound B in 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.

Compound Q is an organic nitrogen compound containing C, H and N, that reacts with dilute sulfuric acid in a 1:1 ratio. 

Suggest a general formula for compound Q.

The elemental analysis by mass of compound Q is: C: 61.22% ; 10.20%, the rest being nitrogen. Determine the empirical and molecular formula of Q.

The ¹³C NMR spectrum of Q shows four peaks. Draw a structure for Q consistent with this information.

Write an equation for the reaction of Q with sulfuric acid.

Bromocyclopentane is an alkyl halide that is a precursor in the synthesis of ketamine. Ketamine is a drug used to induce anaesthesia and treat depression. The structure of ketamine is shown below.

Identify the functional groups in ketamine.

In the boxes draw the organic products for the reactions of bromocyclopentane.

Name all the organic products of the reactions in part b).

Name the inorganic product(s) of the reaction in b).

State the IUPAC name of the following molecule:

2,4,6-triaminotoluene is a useful precursor in the synthesis of aromatic compounds and has the structure shown below:

¹³C spectroscopy can be used to distinguish between isomers in complex organic molecules.

i) State how many positional isomers are possible in 2,4,6-triaminotoluene. 

[1]

ii) Explain how the ¹³C NMR spectrum would enable a student to distinguish between positional isomers of 2,4,6-triaminotoluene.

[2]

In the box, draw the starting material for the reaction shown below:

A derivative of 2,4,6-triaminotoluene called 2,4,6-tri(aminomethyl)toluene is shown below. Complete the structure of the reactant in the box.

A student was preparing 2,4,6-tri(aminomethyl)toluene using the reaction in part c). To check their success they made an IR spectrum of the starting material and the product, but unfortunately the student mixed the two unlabelled spectra. One the two spectra is shown below.

State which substance the spectrum belongs to and explain your reasoning.

Tryptophan is a naturally occurring α-amino acid. Its structure is shown below.

Draw a circle around the R group in this amino acid

Deduce the molecular formula for tryptophan and write a balanced equation for the reaction of tryptophan with dilute nitric acid.

Draw the structures for the organic product of the reaction of tryptophan and the following substances:

i) NaOH (aq)

[1]

ii) C₂H₅OH and concentrated sulfuric acid.

[2]

Two more naturally occurring amino acids are leucine and isoleucine shown below:

State how many optical isomers there are for leucine and isoleucine.

The amino acid alanine is shown below:

Alanine will react with excess chloromethane. Draw the structure of the product formed in this reaction. 

Alanine can also react with serine to produce two different dipeptides. The structure of serine is shown below.

Draw both dipeptide formed in this reaction.

Explain the conditions in which alanine exists as a solid and draw the structure of the amino acid in these conditions.