Nitrogen Compounds (A Level Only) (CIE A Level Chemistry)

Three nitrogen containing molecules, ammonia, NH₃, phenylamine, C₆H₅NH₂ and N-methylethylamine, CH₃CH₂NHCH₃, are drawn below respectively in Fig. 1.1.

Fig. 1.1

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Phenylamine, C₆H₅NH₂ shown in Fig. 1.1 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 and leather 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:

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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.

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Methylamine can be prepared from chloromethane.

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Chloroethane can also react with methylamine.

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Two separate solutions of methylamine, CH₃NH₂ and dimethylamine, (CH₃)₂NH, were left unlabelled in a laboratory.

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Much research has been carried out in recent years investigating the exact structure of silk. The silk of a spider's web is at least five times as strong as steel, and twice as elastic as nylon. A silk fibre is composed of many identical protein chains, which are mainly made from the amino acids glycine, alanine and serine, shown in Fig. 3.1, with smaller amounts of four other amino acids.

Fig. 3.1

Amino acids can exist as zwitterions. Draw the zwitterion structure for glycine.

Amino acids can act as acids or bases. Write equations to show:

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The M_r of a silk protein molecule is about 600,000. Assuming it is made from equal amounts of the three amino acids in Fig. 3.1, calculate the average number of amino acid residues in the protein chain.
Show your working.

[M_r (glycine) = 75;   M_r (alanine) = 89;     M_r (serine) = 105]

number of residues .............................................

Phenylamine can be converted into the organic compounds A and B as shown in Fig. 4.1.

Fig. 4.1

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When phenylamine is treated with propanoyl chloride a white crystalline compound, C, C₉H₁₁NO, is formed.

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percentage = ........................ %

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Benzamide can be reduced to form benzylamine.

benzamide	benzylamine

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When benzamide is refluxed with acid, hydrolysis occurs.

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A mixture of amino acids may be separated using electrophoresis. A typical practical set-up is shown in the diagram.

When the power supply is switched on, some amino acids may not move, but remain stationary. Suggest an explanation for this observation.

The amino acid glycine has the formula H₂NCH₂CO₂H. Identify the species formed on the filter paper if glycine moves to the left (positive) end of the filter paper.

The result shown in Fig. 5.1 was obtained from another electrophoresis. 

Fig. 5.1

What can be deduced about the relative sizes of, and charges on, the amino acid species A, B and C?

A tripeptide was formed from three different amino acids, alanine, serine and valine. The structural formulae of the amino acids are shown in Table 5.1.

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