Features of Alkanes. Long chain Alkanes. Increasing length. What is a cyclo-alkane. They are alkanes containing a ring of three or more carbons The have the molecular formula C n H 2n. Where do they come from?. Other organic sources. Physical properties. Boiling points.
What is a cyclo-alkane They are alkanes containing a ring of three or more carbons The have the molecular formula CnH2n
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
Un-branched vs branched alkanes Explain what this graph shows
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.
Properties • Insoluble in water • Unreactive • Extremely weak acids • Highly combustible in oxygen • Release much energy in exothermic reactions.
What two energy patterns do you observe in the previous slide? • 1 • 2