ASRJC H2 Chem 9. Alkanes

2024 JC1 H2 Hydrocarbons: Alkanes 2024/ASRJC/Chemistry 1 ANDERSON SERANGOON JUNIOR COLLEGE JC1 H2 CHEMISTRY HYDROCARBONS: ALKANES Lecture Outline Content 1 Introduction 2 Nomenclature 3 Physical properties 4 Isomerism in alkanes 5 Chemical reactivity of alkanes 6 Chemical reactions of alkanes 7 Chemical reactions of alkanes 8 Hydrocarbon as fuels 9 Car engines emissions and the environmental consequences 10 Conservation of finite resources Learning Outcomes Candidates should be able to: (a) explain the general unreactivity of alkanes, including towards polar reagents (b) describe the chemistry of alkanes as exemplified by the following reactions of ethane: (i) combustion (ii) free–radical substitution by chlorine and by bromine (c) describe the mechanism of free –radical substitution with particular reference to the initiation, propagation and termination reactions (d) recognise the environmental consequences of: (i) carbon monoxide, oxides of nitrogen and unburnt hydrocarbons arising from the internal combustion engine and their catalytic removal (ii) gases that contribute to enhanced greenhouse effect (e) recognise that petroleum, a chemical feedstock, is a finite resource and the importance of recycling References 1. Chemistry for Advanced Level, Peter Cann, 2002 2. Chemistry, The Molecular nature of Matter and Change, Silberberg, 2003 3. Chemistry (2nd edition). Chris Conoley and Phil Hill 4. Chemistry in Context. Hill & Holman 5. Understanding Chemistry for Advanced Level. Ted Lister, Janet Renshaw

2024 JC1 H2 Hydrocarbons: Alkanes 2024/ASRJC/Chemistry 2 1. Introduction Hydrocarbons  Hydrocarbons are compounds containing only hydrogen and carbon, and are obtained from crude oil, a fossil fuel.  It is a major energy source.  Alkanes constitute the major part of crude oil. Alkanes are transformed into feedstock for the chemical industry and fuels in internal combustion engines, jet engines and power stations (See Section 8). Huge fractions of energy we use come from combustion of alkanes. Hydrocarbons Alkanes Alkenes Arenes Alkynes (for your information only)

2024 JC1 H2 Hydrocarbons: Alkanes 2024/ASRJC/Chemistry 3 Alkanes  Alkanes are saturated hydrocarbons. All the carbon atoms are joined by single covalent bonds only.  Each C atom is sp3 hybridised, tetrahedrally surrounded by H and other C atoms.  Alkanes can exist as straight chains, branched chains, and rings.  Saturated hydrocarbons with one or more rings of carbon are known as cycloalkanes.  General formula: • for open–chain (i.e. straight–chain and branched–chain) alkanes: CnH2n+2, • for cycloalkanes: CnH2n ; where n equals the number of carbon atoms.  If a hydrogen atom is removed from an alkane, the partial structure that remains is called an alkyl group (usually denoted as R, R’ etc.). Examples of straight–chain and branched–ch