Leaving Certificate Chemistry Organic Chemistry 33 The Carboxylic Acids Leaving Certificate Chemistry

The First 4 Carboxylic Acids Structural Formulae Methanoic Acid: HCOOH O group present ― ― 1 Carbon-Long ― C ― OH O H C OH

The First 4 Carboxylic Acids Structural Formulae Ethanoic Acid: CH3COOH O ― ― 2 Carbons Long ― C ― OH group present H O H C C OH H

The First 4 Carboxylic Acids Structural Formulae Propanoic Acid: C2H5COOH O ― ― 3 Carbons Long ― C ― OH group present H H O H C C C OH Food Preservative (Inhibits the growth of bacteria and mold like E. Coli) H H

The First 4 Carboxylic Acids Structural Formulae Butanoic Acid: C3H7COOH O ― ― 4 Carbons Long ― C ― OH group present H H H O H C C C OH C H H H

O OH Benzoic Acid C

Physical Properties of the carboxylic acids Use electronegativity differences to predict what kinds of bonds are present in an carboxylic acid such as ethanoic acids Can you predict whether a carboxylic acid or its corresponding alkane /aldehyde / alcohol would have a higher boiling point? Can you explain why the boiling points of the carboxylic acids increase with the length of the chain? Would the lower or higher members of the carboxylic acids be more soluble in water? HINT – water is polar.

Formation of a carboxylic acid Oxidation of a primary alcohol

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 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

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

Reactions of Ethanoic Acid Mandatory Experiment Reactions of Ethanoic Acid

Tests on ethanoic acid Colourless Liquid Pungent odour

Reaction of an acid with a carbonate

Tests on ethanoic acid 2 2 2 Reaction with sodium carbonate CH3COOH + Na2CO3 2007: Q2 (f) (9) Ethanoic Acid Sodium Carbonate 2009: Q8 (d) (9) 2 2 CH3COONa + H2O H2O + CO2 CH3COONa + + Effervesence (fizzing) of carbon dioxide observed Sodium Ethanoate Water Carbon Dioxide Sodium Ethanoate Water

Reaction of an acid with magnesium

Tests on ethanoic acid 2 Reaction with magnesium CH3COOH + Mg Magnesium metal (CH3COO)2Mg + H2 Effervesence (fizzing)

Reaction of an acid and an alcohol (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

Mandatory experiment Preparation of Benzoic acud

Mandatory experiment Recrystallization of Benzoic acid