Features of Alkanes - PowerPoint PPT Presentation

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Features of Alkanes
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Features of Alkanes

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  1. Features of Alkanes

  2. Long chain Alkanes

  3. Increasing length

  4. What is a cyclo-alkane They are alkanes containing a ring of three or more carbons The have the molecular formula CnH2n

  5. Where do they come from?

  6. Other organic sources

  7. Physical properties

  8. Boiling points • Attractive forces between the molecules that hold them together are called Van der Waals forces • To vapourise the hydrocarbon these must be overcome by putting in energy • The longer the chain – the more energy required so the higher the boiling point

  9. Un-branched vs branched alkanes Explain what this graph shows

  10. Branched structures • The more branched the more compact • The more compact the less attraction points it has with other molecules • The less attraction the lower the boiling point. • Branched alkanes therefore have lower BPs than their un-branched isomers.

  11. Properties • Insoluble in water • Unreactive • Extremely weak acids • Highly combustible in oxygen • Release much energy in exothermic reactions.

  12. Heats of Combustion (-ΔH°) of several alkanes and branched alkane

  13. What two energy patterns do you observe in the previous slide? • 1 • 2

  14. Heat of combustion and stability

  15. Oxidation numbers of Carbon in alkanes