Edexcel International A Level Chemistry Introduction to Organic Chemistry Exam Questions

About Edexcel International A Level Chemistry Introduction to Organic Chemistry

Introduction to organic chemistry sets out the language you use for every organic topic in Edexcel International A Level Chemistry. In Unit 1 you learn how to name compounds using IUPAC rules, how to represent them with general, structural, displayed and skeletal formulae, and how members of a homologous series share a functional group and similar chemical properties. It also introduces structural isomerism and the main types of reaction and reagent. This topic leads directly into Alkanes and Alkenes. Examiners often test naming of branched compounds, drawing isomers for a given molecular formula, and the difference between a hazard and a risk in organic practical work.

What you need to know

• Homologous series A homologous series has the same general formula and functional group, with each member differing by CH2. Members show similar chemical properties and a gradual trend in physical properties such as boiling temperature.
• Types of formulae Know empirical, molecular, general, structural, displayed and skeletal formulae. In skeletal formulae each line end or vertex is a carbon atom and hydrogens on carbon are not drawn.
• IUPAC naming Find the longest carbon chain, number from the end that gives the lowest locants to substituents, and list substituents alphabetically with prefixes di, tri and so on.
• Structural isomerism Structural isomers have the same molecular formula but different structural formulae. They can be chain isomers, position isomers or functional group isomers.
• Types of reaction Classify reactions as addition, substitution, elimination, oxidation, reduction or polymerisation. Classify reagents as radicals, electrophiles or nucleophiles.
• Hazard and risk A hazard is something with the potential to cause harm, such as a flammable or toxic substance. A risk is the chance that harm will occur, which can be reduced by measures such as using a fume cupboard or a water bath instead of a naked flame.

Common mistakes in Introduction to Organic Chemistry

• Numbering a chain from the wrong end, giving names such as 3-methylbutane instead of 2-methylbutane. Choose the numbering that gives the lowest locants.
• Missing a longer carbon chain hidden in a bent or branched drawing. Always check every possible path through the carbon skeleton.
• Drawing the same molecule twice when asked for isomers, for example by flipping it. Name each structure to check they are different.
• Confusing hazard and risk. The hazard is the property of the substance; the risk depends on how it is handled.
• Leaving hydrogen atoms off displayed formulae. A displayed formula shows every atom and every bond.

Try three Introduction to Organic Chemistry exam-style questions