Edexcel IGCSE Chemistry – Organic Chemistry

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Organic Compound
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Compound containing carbon (but not metal carbonate, carbon dioxide or carbon monoxide)
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Homologous Series
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Family of compounds with same functional group, same general formula, similar chemical properties, adjacent members differ by CH2 and they show a gradiation in physical properties
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Hydrocarbon
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Compounds that are ONLY made of hydrogen and carbon. Two types – saturated and unsaturated
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Saturated Hydrocarbon
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Contains C-C single bond – alkanes – can’t change colour of bromine water
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Unsaturated Hydrocarbon
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Contains C=C double bond – alkenes – can change the colour of bromine water
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General Formula
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Confirms which compound is in which homologous series e.g. alkanes CnH2n+2, alkenes CnH2n
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Functional Group
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Atom or group of atoms that control the property of homologous series e.g. Alkane -single bond, Alkene -double bond, Alcohol -OH, Carboxylic Acid -COOH
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Isomerism
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Molecules with identical molecular formulae but with different structural formulae
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Alkanes
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General formula = CnH2n+2 eg methane CH4, Ethane C2H6
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Products of complete combustion of alkanes
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CH4 + O2 = CO2 + H2O
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Products of incomplete combustion of alkanes
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CH4 + O2 = CO + H2O or CH4 + O2 = C (s) + H2O
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Substitution Reaction
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Where hydrogen atoms of alkanes are replace by halogen atoms eg methane + bromine in UV Light = bromomethane
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General Formula of Alkenes
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CnH2n e.g. ethene, propene C3H6
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Addition Reaction
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With Hydrogen: In the presence of nickel catalyst alkenes react with hydrogen = alkanes. (hydrogenation) With Halogen: An alkene will make its double bond into a single bond to bond to two bromines. (halogenation).
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Test for alkenes (unsaturated hydrocarbon)
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Shake unknown hydrocarbon with bromine water – if compound is unsaturated then colour will change from orange to colourless.
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General Formula for Alkanes
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CnH2n+2
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General Formula for Alcohols
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CnH2n+1 OH
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General Formula for Carboxylic Acid
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CnH2n+1 COOH
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General Formula for Amines
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CnH2n+1 NH2
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Alkane with 1 Carbon atom
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Methane
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Alkane with 2 Carbon atoms
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Ethane
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Alkane with 3 Carbon atoms
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Propane
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Alkane with 4 Carbon atoms
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Butane
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Alkane with 5 Carbon atoms
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Pentane
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Alkene with 2 C
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Ethene
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Alkene with 3 C
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Propene
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Alkene with 4 C
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Butene
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Alkene with 5 C
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Pentene
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How to manufacture Ethanol by catalyst
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Pass Ethene & steam over phosphoric acid catalyst – 300 degrees C – pressure 60-70 atm
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How to manufacture Ethanol by fermentation
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Glucose solution mixed with yeast – mixture produced after a few days – dilute solution of ethanol 12%. – enzymes work at 37 degrees C – mixture filtered to remove solid impurities – fractionally distilled to further purify
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Formula for ethanol by catalyst
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Ethane + steam -> Ethanol CH2=CH2 (g) + H2O (g) -> CH3CH2OH
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Formula for ethanol by fermation (of sugars)
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Glucose solution -> ethanol + carbon dioxide C6H12O6 (aq) -> 2C2H5OH (aq) + 2CO2 (g)
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Facts about producing ethanol by fermentation of sugars
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Renewable resources Batch process – inefficient Slow – takes several days Produces impure ethanol (further processing) Uses gentle temps and ordinary pressure (low energy)
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Facts about producing ethanol by hydration of ethane
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Finite resources (crude oil) Continuous flow process (efficient) Rapid Produces purer ethanol High temp and pressures (high energy)
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Dehydration of ethanol to ethene
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Removes water from ethanol by passing ethanol vapour over hot aluminium oxide (catalyst). C2H5OH -> C2H4 + H2O (works for propanol -> propene too)

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