Edexcel International A Level Chemistry
Edexcel International A Level Chemistry General Principles of Organic Reactions Exam Questions
Free Edexcel International A Level Chemistry exam questions for General Principles of Organic Reactions, with a mark scheme for every pack. Covers organic reaction types, homolytic and heterolytic bond fission, radicals, nucleophiles and electrophiles, curly arrows and classifying organic compounds.
General Principles of Organic Reactions exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
StemUp mark scheme flashcards
A-Level Chemistry Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
From £10.99View flashcards
About Edexcel International A Level Chemistry General Principles of Organic Reactions
General principles in Unit 2 of Edexcel International A Level Chemistry pulls together the ideas that underpin organic mechanisms before you study Halogenoalkanes, Alcohols and Mass spectra and IR. You revisit how reactions are classified (addition, substitution, elimination, oxidation, reduction, hydrolysis, polymerisation) and how bonds break homolytically to give radicals or heterolytically to give ions. You also learn to identify nucleophiles and electrophiles and use curly arrows correctly. Examiners test these ideas inside mechanism questions, so precise use of the terms and correctly placed arrows can gain or lose several marks across a paper.
What you need to know
- Types of reaction Organic reactions are classified as addition, substitution, elimination, hydrolysis, oxidation, reduction and polymerisation. You should be able to identify the type from an equation.
- Bond fission Homolytic fission splits a bond so each atom takes one electron, forming radicals. Heterolytic fission gives both electrons to one atom, forming a positive and a negative ion.
- Reagent types A nucleophile is a lone pair donor that attacks an electron deficient carbon, for example OH-, CN- and NH3. An electrophile is an electron pair acceptor, for example H+ or the delta positive end of HBr.
- Curly arrows A curly arrow shows the movement of a pair of electrons. It must start from a lone pair or a bond and end at an atom or at a position where a new bond forms.
- Primary, secondary and tertiary Halogenoalkanes and alcohols are classified by the number of carbons attached to the carbon bearing the functional group. This affects their rates of reaction and oxidation products.
- Mechanism names Each mechanism name combines the reagent type and the reaction type, for example free radical substitution, electrophilic addition, nucleophilic substitution.
Common mistakes in General Principles of Organic Reactions
- Starting curly arrows from an atom symbol or a positive charge instead of a lone pair or bond.
- Describing a nucleophile as something attracted to a positive charge without mentioning the lone pair it donates.
- Confusing homolytic and heterolytic fission. Homolytic gives radicals, heterolytic gives ions.
- Misclassifying hydrolysis as simple substitution without recognising the role of water or hydroxide ions.
- Labelling a carbon as tertiary based on the number of hydrogens rather than the number of carbon atoms attached.
Try three General Principles of Organic Reactions exam-style questions
1. Define the terms nucleophile and electrophile. (2 marks)
Show the mark scheme answer
Nucleophile: a species that donates a lone pair of electrons (to form a covalent bond); electrophile: a species that accepts a pair of electrons.
2. Explain the difference between homolytic and heterolytic bond fission, giving the type of species formed in each. (2 marks)
Show the mark scheme answer
Homolytic fission: each atom takes one electron from the bond, forming radicals; heterolytic fission: one atom takes both electrons, forming a positive ion and a negative ion.
3. Classify each reaction: (a) C2H4 + Br2 gives C2H4Br2; (b) C2H5Br + OH- gives C2H5OH + Br-; (c) C2H5OH gives C2H4 + H2O. (3 marks)
Show the mark scheme answer
(a) addition (electrophilic); (b) substitution (nucleophilic) or hydrolysis; (c) elimination (dehydration).
General Principles of Organic Reactions FAQs
What does Edexcel International A Level Chemistry General principles cover?
In this unit it covers the classification of organic reactions and reagents, homolytic and heterolytic fission, radicals, nucleophiles and electrophiles, curly arrow conventions and primary, secondary and tertiary classification.
How do I revise General principles?
Make a glossary of the key terms with precise definitions, then practise labelling the reagent and reaction type in every mechanism you meet in Units 1 and 2.
Why does this topic matter for mechanisms?
Every mechanism mark scheme rewards correctly placed curly arrows, partial charges and the right intermediate, so mastering these principles makes every later organic mechanism easier.
