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Organic Chemistry 10 Chemistry Quiz Alkanes • General Formula • Description • Combustion • Reactivity • Chemical test • Uses • CnH2n+2 • Saturated • Burns in Oxygen to form CO2 + H20 (CO with low O2) • Low • None • Fuels The chlorination of methane • Halogenation is the replacement of one or more hydrogens in an organic compound by halogen atoms • When methane is reacted with chlorine the products of the reaction depend on whether there is an excess of methane or chlorine • If there is an excess of methane it form chloromethane and hydrogen chloride To do • Write down a word equation for the chlorination of methane • Can you write a chemical equation? • How about a full balanced chemical equation? Movie Halogenation methane chlorine chloromethane hydrogen chloride CH 4 Cl2 CH3Cl HCl CH 4 ( g ) Cl2 ( g ) CH3Cl ( g ) HCl ( g ) With an excess of chlorine a mixture of products is formed. Chlorine can obviously replace up to 4 of the hydrogen atoms. Why halogenation? • These products are generally used as intermediate compound for further synthesis Natural Gas and Oil Separating the fractions Fractional distillation • Preheated crude oil is pumped into the column (340 C) • The vapour in the crude oil rises due to differences in density with different fractions condensing in different regions • The liquid part of the crude oil sinks in the column • The low density fractions are thin and light coloured, the high density fractions are ‘viscous’ and dark How does it work? • Components separate due to different boiling points • Crude oil is a mixture of hydrocarbons • Molecules are chemically bonded with strong covalent bonds but contain different numbers of carbon atoms Go on… • The weak attractive forces between the molecules have to be broken if the hydrocarbon is to boil • The longer the hydrocarbon molecule is, the stronger the intermolecular forces are • The shorter chains are more volatile – they form a vapour Boiling Volatility • We can smell petrol (gasoline) much easier than we can smell engine oil • This is because petrol has 5-10 carbon atoms and engine oil has 14-20 carbons atoms Combustion combustion Viscosity Viscosity Homework • Go to: http://www.rscoilstrike.org/preloader.swf • Play the game • Take a screen shot (print screen) or use the snipping tool to take an A4 image • Print this out and stick it in • Winner (most money) gets a ‘get out of homework free’ card Incomplete Combustion Alkanes The end of year test • Can contain ANYTHING we have covered over the course of this year (see specific learning objectives) • May contain anything from the Organic Chemistry too Origami time Youtube Homologous series • A family of hydrocarbons is a homologous series • This means they have the same functional groups • You can have alcohols (ROH), alkanes (RH), Haloalkanes (RX) and MANY OTHERS Roger Frost Isomerism • Hydrocarbons are based upon the number of carbon atoms • The carbon atoms can be rearranged in different ways: these are called isomers Alkenes Alkenes • • • • • Formed from cracking One or more double carbon bond Hence unsaturated Reactivity due to double bond Tested with bromine water Alkenes Alkenes • General Formula • Description • Combustion • Reactivity • Chemical test • Uses • CnH2n • unsaturated • Burns in Oxygen to form CO2 + H20 (CO with low O 2) • High (double bond), undergo addition reactions • Turns bromine water from brown to colourless • Making polymers Isomers of Alkenes Questions • Q1 (a) Draw displayed formulae for hexene • (b) Describe a test to distinguish between hexane and hexene • Q2 Draw two isomers of pentene • Homework: revise Next lesson • Oil spill clean up