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Edexcel IAL Chemistry Topic 20 Organic Synthesis

Topic 20 questions combine analytical data with synthesis planning: calculate formulae, identify functional groups, choose reagents and justify purification or separation steps.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Deduce empirical, molecular and structural formulae from combustion and spectral data.
  • Complete synthesis routes with reagents, intermediates and functional-group changes.
  • Choose purification or separation methods such as distillation, reflux or chromatography.

Covered syllabus points

20.1—Deduce the empirical formulae, molecular formulae and structural formulae from data drawn from combustion analysis, element20.2—Methods of increasing the length of the carbon chain in a molecule by the use of magnesium to form Grignard reagents and20.3—Knowledge of organic chemistry contained given in this specification to solve problems such as: i predicting the properties20.4—CORE PRACTICAL 16 The preparation of aspirin20.5—The following techniques used in the preparation and purification of organic compounds: i refluxing ii purification by

Topic 20: Organic Synthesis question 1

[Maximum number: 4]

This question concerns six isomers each with the molecular formula C5H10O2\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}.

Isomer F is a neutral compound that smells of pears.

It can be formed by the reaction between compounds V and W in the presence of concentrated sulfuric acid.

Compound V has an absorption in its infrared spectrum at 1720 cm−11720 \mathrm{~cm}^{-1} and a broad absorption around 3050 cm−13050 \mathrm{~cm}^{-1}.

Compound W can be formed directly from propanal.

Identify, by name or formula, compounds V, W and F.

Justify your answer by using all the available information.

Topic 20: Organic Synthesis question 2

[Maximum number: 6]

Benzoic acid is a white crystalline solid with the structure shown.

Figure for Question Topic 20: Organic Synthesis question 2 — Edexcel A-Level Chemistry A2

It is found in many plants as it is an important building block for the biosynthesis of a variety of compounds, such as plant hormones and attractants for pollinators.

The role of benzoic acid in the chemical industry is also widespread and approximately 500000 tonnes are produced annually. It is used in the synthesis of many compounds, including medicines, dyes and insect repellents.

Such synthetic dyes are often classified as aryl azo dyes. These dyes have a range of vivid colours and a wide range of uses in many industries, including food and textiles. Their synthesis involves the formation of a diazonium ion. This ion then reacts with a phenol in a coupling reaction, to form the dye. The relative simplicity of the reactions involved and ready availability of starting materials make azo dyes cheap to produce.

Salts of benzoic acid, such as calcium benzoate and sodium benzoate, are used in the food industry as preservatives.

Devise a reaction scheme to produce benzoic acid from benzene, via bromobenzene and then a Grignard reagent.

Include the reagents and essential conditions for each step and give the name or structure of each of the intermediate compounds.

Details of practical procedures and reaction mechanisms are not required.

Topic 20: Organic Synthesis question 3

[Maximum number: 7]

This question is about benzene and some of its compounds.

Devise a synthesis to convert bromobenzene into benzamide.

Include reagents, conditions and the structures of the intermediate compounds.

Figure for Question Topic 20: Organic Synthesis question 3 — Edexcel A-Level Chemistry A2
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