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Leaving Certificate Chemistry
Organic Chemistry The Alcohols Leaving Certificate Chemistry
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The alcohols are a group of organic compounds in which one (or more) of the hydrogen atoms of an alkane have been replaced by an –OH hydroxyl group.
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The First 4 Alcohols Structural Formulae
Methanol: CH3OH -OH Group present 1 Carbon-Long H H C OH H
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The First 4 Alcohols Structural Formulae
Ethanol: C2H5OH Other Uses -OH Group Present 2 Carbon Longest Chain H H C6H12O6 2 C2H5OH + 2 CO2 H C C OH Glucose Ethanol H H Produced in industry by fermentation Fuel Solvent Thermometer
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The First 4 Alcohols Structural Formulae
Propanol: C3H7OH -OH Group Present 3 Carbon Longest Chain H H H H C C C H OH H H H
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The First 4 Alcohols Structural Formulae
Butanol: C4H9OH -OH Group Ptresent 4 Carbon Longest Chain H H H H H C C C C OH H H H H
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Primary & Secondary Alcohols
A primary alcohol is an alcohol in which the carbon atom that is bonded to the –OH (hydroxyl) group is itself also bonded to ONE other carbon atom A secondary alcohol is an alcohol in which the carbon atom that is bonded to the –OH (hydroxyl) group is itself also bonded to TWO other carbon atoms. H H H Propan-1-ol Propan-2-ol H C C C OH H H OH H H
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Physical Properties of the Alcohols
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Would you expect alcohols to have higher boiling points than alkanes/ Why?
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Comparing the boiling points of the alkanes and the alcohols
2006 Q. 10 (c) 450 Boiling point in Kelvins 400 350 119 K Liquid 300 Gas 250 226.5 K 200 Number of Carbons 150 100 50 1 2 3 4
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Why does each alcohol have a higher boiling point than its corresponding alkane?
Each alcohol has a higher relative molecular mass than its corresponding alkane 2006 Q. 10 (c) (7) Alcohols have strong intermolecular hydrogen bonding forces whereas alkanes are influenced by much weaker Van Der Waals forces.
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H ∂— H C O H ∂+ H H O H C H H
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Why is the difference in boiling points between methane and methanol K whilst the difference in boiling points between butane and butanol is only 119 K? Because the strength of the hydrogen bonding is much weaker in butanol than it is in methanol 2006 Q. 10 (c) (6) This helps to explain why butanol is virtually insoluble (slightly soluble) in water whereas methanol is very soluble in water
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Would you expect alcohols to be soluble in water/ Why?
Would you expect all members of the alcohol family to be equally soluble in water? Why? Would you expect alcohols to be soluble in water/ Why?
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Chemical Reactions of the Alcohols
Combustion
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Combustion CH3OH 1½ O2 CO2 2 H2O C2H5OH 3 O2 2 CO2 3 H2O
Carbon Dioxide Methanol Oxygen Water C2H5OH 3 O2 2 CO2 3 H2O Carbon Dioxide Ethanol Oxygen Water
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Chemical Reactions of the Alcohols
Elimination
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Dehydration (elimination)
C C H C C OH H H Aluminium Oxide [catalyst] Al2O3 Ethene H H Ethanol This is an elimination reaction Formation of a saturated compound Loss of a small molecule like water H2O Water 2007 Q. 8 (a) (6)
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Elimination reactions of alcohols
Draw the structural formulas and name the products of an elimination reaction to Propanol Butanol
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Dehydration (elimination)
Propanol H H H H C C C OH H H H Aluminium Oxide H H C C C C H2O Water H H H Propene
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Dehydration (elimination)
Butanol H H H H H C C C C OH H H H H Aluminium Oxide H H H C C H2O C C H Water H H H Butene H
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Chemical Reactions of the Alcohols
Oxidation
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Oxidation of a primary alcohol
Methanol CH3OH O H H Acidified Sodium Dichromate H C H H C OH Methanal HCHO H H O H C OH Excess Methanoic Acid HCOOH
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Oxidation of a primary alcohol
Ethanol C2H5OH H Acidified Sodium Dichromate H H H C C OH H H H H O H O H C C H Excess H C C OH Ethanoic Acid CH3COOH Ethanal CH3CHO H H
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Oxidation of a primary alcohol
Acidified Sodium Dichromate H H H Propanoic Acid C2H5COOH Propanol C3H7OH Propanal C2H5CHO Excess
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Oxidation of a primary alcohol
Butanol Butanal Butanoic Acid On reaction with acidified sodium dichromate In Excess
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The Alcohols The Aldehydes The Carboxylic Acids Ethanol C2H5OH
Acidified sodium dichromate Hydrogen, Nickel catalyst Oxidation Reduction The Aldehydes Ethanal CH3CHO Acidified sodium dichromate Reduction Hydrogen, Nickel catalyst Oxidation The Carboxylic Acids Ethanoic Acid CH3COOH
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Oxidation of a secondary alcohol
Acidified Sodium Dichromate H H H Propanone Propan-2-ol Nail Varnish Remover Oxidation of a secondary alcohol produces a ketone
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Oxidation of a secondary alcohol
Acidified Sodium Dichromate H H H H Butanone Butan-2-ol Oxidation of a secondary alcohol produces a ketone
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The Ketones The Alcohols The Aldehydes The Carboxylic Acids
Oxidation of a secondary alcohol The Ketones Acidified sodium dichromate The Alcohols H2, Ni Reduction Propanone from propan-2-ol Ethanol C2H5OH Acidified sodium dichromate Hydrogen, Nickel catalyst Oxidation Reduction The Aldehydes Ethanal CH3CHO Acidified sodium dichromate Reduction Hydrogen, Nickel catalyst Oxidation The Carboxylic Acids Ethanoic Acid CH3COOH
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Chemical Reactions of the Alcohols
The reaction of ethanol with sodium
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Reaction of ethanol with sodium
Na 2 Sodium Hydrogen H H Sodium Ethoxide Ethanol C2H5OH Na C2H5ONa H2 Ethanol Sodium Hydrogen Sodium Ethoxide
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Chemical Reactions of the Alcohols
Reaction with an acid (formation of an ester)
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Esterification Ethyl Ethanoate CH3COOC2H5 CH3COOH CH3COOC2H5 H2O
Ethanoic Acid CH3COOH H C C O H H Ethyl Ethanoate CH3COOC2H5 Ethyl Group H H H CH3COOH CH3COOC2H5 O C C H Ethanol C2H5OH H2SO4 H2O C2H5OH H H
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Esterification Methyl Propanoate C2H5COOCH3 H2O Propanoic Acid
C2H5COOH H H Methyl Group Methyl Propanoate C2H5COOCH3 H H O C H Methanol CH3OH H2O H
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The Alkanes - H2 The Chloroalkanes + H2 The Alkenes + HCl , + Cl2
Substitution using UV Light Ethane C2H6 - H2 The Chloroalkanes + H2 Chloroethane C2H5Cl The Alkenes + HCl , + Cl2 Ethene C2H4 + H2O The Alcohols Ethanol C2H5OH - H2O Aluminium Oxide Catalyst The Polymers Polythene & Polypropene
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