Edexcel Jan 2015 (IAL) Paper 5 Q24

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SECTION C Answer ALL the questions. Write your answers in the spaces provided. 24 Organic Nitrogen Chemistry Organic compounds that contain nitrogen are vital to life, but are also important in everyday applications of chemistry. The simplest organic nitrogen compounds are amines, which may be regarded as derivatives of ammonia in which one or more of the hydrogen atoms of ammonia have been replaced by an alkyl group or an aryl group. Some simple amines are shown below. H3C NH2 H3C H3C NH methylamine dimethylamine H3C CH3 H3C trimethylamine NH2 phenylamine (aniline) Amines with one alkyl group are called primary, with two alkyl groups secondary and with three alkyl groups tertiary. Because of the presence of nitrogen, the physical and chemical properties of alkyl amines are similar to those of ammonia but the similarities are less marked with phenylamine. Amides are carboxylic acid derivatives which have a carbonyl group adjacent to an amine group. The simplest amide is ethanamide: H3C C NH2 ethanamide Because the two groups are adjacent, the chemical properties of amides are different from those of amines. Amino acids are compounds with an amine group and a carboxylic acid group. The presence of these two functional groups gives amino acids properties that are also different from those of amines. The great significance of the amino acids is their ability to form polymers called polypeptides, leading to the formation of proteins, the building blocks of life. To form polypeptides, amino acids are joined by the amide group, sometimes called the peptide link. *P45045A02328* 23 Turn over<br /> (a) Methylamine boils at 267 K and dissolves in water to form an alkaline solution. (i) Explain why methylamine has a higher boiling temperature than ammonia. A detailed description of the forces involved is not required. (2)*(ii) Explain why primary amines are soluble in water but their solubility decreases as molar mass increases. (3)(iii) Write an equation for the reaction of methylamine with water to produce an alkaline solution. State symbols are not required. (1) 24 *P45045A02428*<br /> (iv) Suggest why dimethylamine is more basic than methylamine and why both are much more basic than phenylamine. (3)(b) The interaction of the carbonyl group and the amine group in ethanamide may be shown by the following diagram. H3C C NH2 (i) Explain what each of the two arrows represents. (2) Arrow 1Arrow 2(ii) Draw a diagram showing the ethanamide molecule if the changes indicated by the arrows go to completion. (1) *P45045A02528* 25 Turn over<br /> (iii) Suggest why the carbonyl group in an amide does not react with 2,4-dinitrophenylhydrazine. (1)(c) The structures of the two simplest amino acids are shown below. H2N H2C OH glycine H2N HC H3C OH alanine (i) Draw the structures of the two compounds, called dipeptides, that can be formed when glycine and alanine combine. Any double bonds must be displayed. (2) 26 *P45045A02628*<br /> (ii) In practice, glycine and alanine do not combine readily. Suggest a reason for this. (1)*(iii) Describe in outline how a mixture of amino acids can be separated and identified using thin layer chromatography. You may assume that a suitable solvent is available. (3)(Total for Question 24 = 19 marks) TOTAL FOR SECTION C = 19 MARKS TOTAL FOR PAPER = 90 MARKS *P45045A02728* 27<br />

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