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*Revision Materials* 1 Atomic Structure 2 Atoms, molecules and stoichiometry 3 Chemical Bonding 4 States of matter 5 Chemical energetics 6 Electrochemistry 7 Equilibria 8 Reaction kinetics 9 The Periodic Table, chemical periodicity 10 Group 2 11 Group 17 12 Nitrogen and sulfur 13 Organic 14 Hydrocarbons 15 Halogen compounds 16 Hydroxy compounds 17 Carbonyl compounds 18 Carboxylic acids and derivatives 19 Nitrogen compounds 20 Polymerisation 21 Organic synthesis 22 Analytical techniques 23 Chemical energetics 24 Electrochemistry 25 Equilibria 26 Reaction kinetics 27 Group 2 28 Chemistry of transition elements 29 Organic 30 Hydrocarbons 31 Halogen compounds 32 Hydroxy compounds 33 Carboxylic acids and derivatives 34 Nitrogen compounds 35 Polymerisation 36 Organic synthesis 37 Analytical techniques

36 Organic synthesis

36.1 Organic synthesis

Organic Synthesis

Specification Reference Organic Chemistry, Synthesis 36.1

Quick Notes

  • Functional groups dictate physical properties and reactivity.
  • Common groups: –OH (alcohol), –COOH (carboxylic acid), –NH2 (amine), –C≡N (nitrile), –COCl (acyl chloride).
  • Predict properties: e.g. alcohols hydrogen bond, amines act as bases, esters hydrolyse.
  • Think in reactivity pathways (oxidation, substitution, hydrolysis, etc.).
  • Multi-step synthesis focuses on converting one functional group into another.

Full Notes

Identifying Functional Groups

To predict the behaviour of an organic molecule, you must first identify its functional groups. These are specific atoms or groups of atoms that dictate how the molecule reacts.

(The required functional groups for CIE can be found here).

How to identify them: Look at the structure and think about which reactions you’ve studied (oxidation, hydrolysis, substitution, etc.) that are specific to each group.

Predicting Properties and Reactions

Once the functional groups are identified, you can make predictions about:

Photo of Matt
Matt’s exam tip

Think in terms of reactivity pathways. For example: An alcohol can be oxidised to an aldehyde to a carboxylic acid. A nitrile can be hydrolysed to a carboxylic acid. An acyl chloride can react with amines to form an amide.

Devising Synthetic Routes

Break complex synthesis into smaller steps, and select appropriate reactions to move between functional groups.

Photo of Matt
Matt’s exam tip

Synthesis questions can look overwhelming! Focus on one thing at a time and remember that no matter how complicated the molecules may look, the functional group conversions will only be ones you have seen and learnt about before. Focus on the functional groups in the molecules that are changing, rather than focusing on the whole molecules overall.

Example Synthesising Ethylamine (C2H5NH2) from Ethene (C2H4)

A typical exam question may get you to fill in missing steps for a synthesis. Such as making ethylamine from ethene.

CIE A-Level Chemistry multi-step synthesis prompt showing ethene converting through three steps to ethylamine, with missing reagents to be filled in.

A possible route may be.

  1. Hydration of Ethene to Ethanol
    Reagents: Steam, H3PO4 catalyst
    C2H4 + H2O → C2H5OH
  2. Conversion of Ethanol to Bromoethane
    Reagents: HBr
    C2H5OH + HBr → C2H5Br + H2O
  3. Nucleophilic Substitution with Ammonia
    Reagents: Excess NH3
    C2H5Br + NH3 → C2H5NH2 + HBr
CIE A-Level Chemistry completed route showing ethene hydrated to ethanol, converted to bromoethane, then to ethylamine using excess ammonia.

Analysing Synthetic Routes

You may be given a sequence and asked to:

Understanding by-products is important for evaluating:

Mastering organic synthesis is about recognising patterns and linking reactions. The more familiar you are with the reactions in the syllabus, the more confidently you’ll be able to plan or analyse a synthesis pathway. Practice plenty of past paper questions to help.

Summary