Leaving Certificate Chemistry Organic Chemistry The Alcohols Leaving Certificate Chemistry

The alcohols are a group of organic compounds in which one (or more) of the hydrogen atoms of an alkane have been replaced by an –OH hydroxyl group.

The First 4 Alcohols Structural Formulae Methanol: CH3OH -OH Group present 1 Carbon-Long H H C OH H

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

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

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

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

Physical Properties of the Alcohols

Would you expect alcohols to have higher boiling points than alkanes/ Why?

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

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.

H ∂— H C O H ∂+ H H O H C H H

Why is the difference in boiling points between methane and methanol 226.5 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

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?

Chemical Reactions of the Alcohols Combustion

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

Chemical Reactions of the Alcohols Elimination

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)

Elimination reactions of alcohols Draw the structural formulas and name the products of an elimination reaction to Propanol Butanol

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

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

Chemical Reactions of the Alcohols Oxidation

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

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

Oxidation of a primary alcohol Acidified Sodium Dichromate H H H Propanoic Acid C2H5COOH Propanol C3H7OH Propanal C2H5CHO Excess

Oxidation of a primary alcohol Butanol Butanal Butanoic Acid On reaction with acidified sodium dichromate In Excess

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

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

Oxidation of a secondary alcohol Acidified Sodium Dichromate H H H H Butanone Butan-2-ol Oxidation of a secondary alcohol produces a ketone

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

Chemical Reactions of the Alcohols The reaction of ethanol with sodium

Reaction of ethanol with sodium Na 2 Sodium Hydrogen H H Sodium Ethoxide Ethanol C2H5OH Na C2H5ONa ½ H2 Ethanol Sodium Hydrogen Sodium Ethoxide

Chemical Reactions of the Alcohols Reaction with an acid (formation of an ester)

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

Esterification Methyl Propanoate C2H5COOCH3 H2O Propanoic Acid C2H5COOH H H Methyl Group Methyl Propanoate C2H5COOCH3 H H O C H Methanol CH3OH H2O H

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