STRUCTURE OF CARBOXYLIC ACIDS contain the carboxyl functional group COOH the bonds are in a planar arrangement

STRUCTURE OF CARBOXYLIC ACIDS contain the carboxyl functional group COOH the bonds are in a planar arrangement include a carbonyl (C=O) group and a hydroxyl (O-H) group

HOMOLOGOUS SERIES HCOOH CH 3 COOH C 2 H 5 COOH Carboxylic acids form a homologous series

HOMOLOGOUS SERIES HCOOH CH 3 COOH C 2 H 5 COOH With more carbon atoms, there can be structural isomers C 3 H 7 COOH (CH 3 ) 2 CHCOOH

Acids are named according to standard IUPAC rules select the longest chain of C atoms containing the COOH group; remove the e and add oic acid after the basic name number the chain starting with the C in COOH being 1 as in alkanes, prefix with alkyl substituents side chain positions are numbered relative to Carbon atom number 1 e.g. CH 3 - CH(CH 3 ) - CH 2 - CH 2 - COOH is called 4-methylpentanoic acid NAMING CARBOXYLIC ACIDS

Acids are named according to standard IUPAC rules select the longest chain of C atoms containing the COOH group; remove the e and add oic acid after the basic name number the chain starting with the C in COOH being 1 as in alkanes, prefix with alkyl substituents side chain positions are numbered relative to Carbon atom number 1 NAMING CARBOXYLIC ACIDS BUTANOIC ACID2-METHYLPROPANOIC ACID

NAMING CARBOXYLIC ACIDS Acids are named according to standard IUPAC rules Many carboxylic acids are still known under their trivial names, some having been called after characteristic properties or their origin. FormulaSystematic name (trivial name)origin of name HCOOH methanoic acid formic acidlatin for ant CH 3 COOH ethanoic acid acetic acidlatin for vinegar C 6 H 5 COOH benzenecarboxylic acidbenzoic acidfrom benzene

CHEMICAL PROPERTIES Carboxylic acids are weak acids. They can donate protons, but they only partially dissociate into their ions. weak acidsCH 3 COOH (aq) CH 3 COO¯(aq) + H + (aq)

CHEMICAL PROPERTIES Carboxylic acids display typical reactions of an acid and form salts, called carboxylates: 1. acid + base  salt + water, eg. CH 3 COOH + NaOH (aq) ——> CH 3 COO¯Na + (aq) + H 2 O (l) ethanoic acid sodium ethanoate 2. acid + carbonate  salt + water + CO 2, eg. CH 3 COOH + NaCO 3 (aq) ——> CH 3 COO¯Na + (aq) + H 2 O (l) + CO 2 (g) ethanoic acid sodium ethanoate QUALITATIVE ANALYSIS Carboxylic acids are strong enough acids to release CO 2 from carbonates. Phenols are also acidic but not are not strong enough to release CO 2

ESTERIFICATION Reagent(s)alcohol + strong acid catalyst (e.g. conc. H 2 SO 4 ) Conditionsreflux Productester Equation e.g.CH 3 CH 2 OH (l) + CH 3 COOH (l) CH 3 COOC 2 H 5 (l) + H 2 O (l) ethanol ethanoic acid ethyl ethanoate

ESTERIFICATION Reagent(s)alcohol + strong acid catalyst (e.g. conc. H 2 SO 4 ) Conditionsreflux Productester Equation e.g.CH 3 CH 2 OH (l) + CH 3 COOH (l) CH 3 COOC 2 H 5 (l) + H 2 O (l) ethanol ethanoic acid ethyl ethanoate NotesConc. H 2 SO 4 is a dehydrating agent - it removes water causing the equilibrium to move to the right and thus increases the yield of the ester

ESTERIFICATION Reagent(s)alcohol + strong acid catalyst (e.g conc. H 2 SO 4 ) Conditionsreflux Productester Equation e.g.CH 3 CH 2 OH (l) + CH 3 COOH (l) CH 3 COOC 2 H 5 (l) + H 2 O (l) ethanol ethanoic acid ethyl ethanoate NotesConc. H 2 SO 4 is a dehydrating agent - it removes water causing the equilibrium to move to the right and thus increases the yield of the ester Naming estersNamed from the original alcohol and carboxylic acid CH 3 OH + CH 3 COOH  CH 3 COOCH 3 + H 2 O methanol ethanoic acid METHYL ETHANOATE

ESTERS Nomenclaturefirst part from alcohol, second part from acid e.g. methyl ethanoate CH 3 COOCH 3 ETHYL METHANOATE METHYL ETHANOATE

ESTERS StructureSubstitute an organic group for the H in carboxylic acids Nomenclaturefirst part from alcohol, second part from acid e.g. methyl ethanoate CH 3 COOCH 3 PreparationFrom carboxylic acids or acyl chlorides ReactivityUnreactive compared with acids and acyl chlorides ETHYL METHANOATE METHYL ETHANOATE

ESTERS StructureSubstitute an organic group for the H in carboxylic acids Nomenclaturefirst part from alcohol, second part from acid e.g. methyl ethanoate CH 3 COOCH 3 PreparationFrom carboxylic acids or acyl chlorides ReactivityUnreactive compared with acids and acyl chlorides IsomerismEsters are structural isomers of carboxylic acids ETHYL METHANOATE METHYL ETHANOATE

Classification CARBOXYLIC ACID ESTER Functional Group R-COOH R-COOR Name PROPANOIC ACID METHYL ETHANOATE Physical propertiesO-H bond gives rise No hydrogen bonding to hydrogen bonding; insoluble in water get higher boiling point and solubility in water Chemical propertiesacidic fairly unreactive reacts with alcohols hydrolysed to acids STRUCTURAL ISOMERISM – FUNCTIONAL GROUP

USES OF ESTERS Despite being fairly chemically unreactive, esters are useful as... flavouringsapple2-methylbutanoate pear3-methylbutylethanoate banana1-methylbutylethanoate pineapplebutylbutanoate rum2-methylpropylpropanoate solventsnail varnish remover - ethyl ethanoate plasticisers

HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C 2 H 5 OH METHANOIC ETHANOL ACID ETHYL METHANOATE

HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C 2 H 5 OH METHANOIC ETHANOL ACID ETHYL METHANOATE METHYL ETHANOATE

HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C 2 H 5 OH METHANOIC ETHANOL ACID CH 3 COOH + CH 3 OH ETHANOIC METHANOL ACID ETHYL METHANOATE METHYL ETHANOATE

HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL The products of hydrolysis depend on the conditions used... acidic CH 3 COOCH 3 + H 2 O CH 3 COOH + CH 3 OH alkaline CH 3 COOCH 3 + NaOH ——> CH 3 COO¯ Na + + CH 3 OH

HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL The products of hydrolysis depend on the conditions used... acidic CH 3 COOCH 3 + H 2 O CH 3 COOH + CH 3 OH alkaline CH 3 COOCH 3 + NaOH ——> CH 3 COO¯ Na + + CH 3 OH If the hydrolysis takes place under alkaline conditions, the organic product is a water soluble ionic salt

HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL The products of hydrolysis depend on the conditions used... acidic CH 3 COOCH 3 + H 2 O CH 3 COOH + CH 3 OH alkaline CH 3 COOCH 3 + NaOH ——> CH 3 COO¯ Na + + CH 3 OH If the hydrolysis takes place under alkaline conditions, the organic product is a water soluble ionic salt The carboxylic acid can be made by treating the salt with HCl CH 3 COO¯ Na + + HCl ——> CH 3 COOH + NaCl

NATURALLY OCCURING ESTERS - TRIGLYCERIDES triglycerides are the most common component of edible fats and oils they are esters of the alcohol glycerol (propane-1,2,3-triol) Saponification alkaline hydrolysis of triglycerol esters produces soaps a simple soap is the salt of a fatty acid as most oils contain a mixture of triglycerols, soaps are not pure the quality of a soap depends on the oils from which it is made CH 2 OH CHOH CH 2 OH

ACYL CHLORIDES NomenclatureNamed from the corresponding carboxylic acid remove -ic add -yl chloride CH 3 COCl ethanoyl chloride C 6 H 5 COCl benzene carbonyl (benzoyl) chloride Chemical Properties colourless liquids which fume in moist air attacked at the positive carbon centre by nucleophiles these include water, alcohols, ammonia and amines undergo addition-elimination reactions

ACYL CHLORIDES ReagentWater Product(s)carboxylic acid + HCl (fume in moist air / strong acidic solution formed) Conditionsroom temperature EquationCH 3 COCl(l) + H 2 O(l) ——> CH 3 COOH(aq) + HCl(aq) Mechanismaddition-elimination

ACYL CHLORIDES ReagentAlcohols Product(s)ester + hydrogen chloride Conditions reflux in dry (anhydrous) conditions EquationCH 3 COCl(l) + CH 3 OH(l) ——> CH 3 COOCH 3 (l) + HCl(g) Mechanismaddition-elimination Note esters can also be made from acids and alcohols via carboxylic acids slower, reversible, low yield via acyl chlorides faster, better yield, must be dry

ACYL CHLORIDES ReagentAmmonia Product(s)amide + hydrogen chloride Conditions Low temperature and excess ammonia; vigorous reaction. EquationCH 3 COCl(l) + NH 3 (aq) ——> CH 3 CONH 2 (s) + HCl(g) orCH 3 COCl(l) + 2NH 3 (aq) ——> CH 3 CONH 2 (s) + NH 4 Cl(s) Mechanismaddition-elimination

ACYL CHLORIDES ReagentAmines Product(s)N-substituted amide + hydrogen chloride Conditions anhydrous EquationCH 3 COCl + C 2 H 5 NH 2 ——> CH 3 CONHC 2 H 5 + HCl orCH 3 COCl + 2C 2 H 5 NH 2 ——> CH 3 CONHC 2 H 5 + C 2 H 5 NH 3 Cl Mechanismaddition-elimination - similar to that with ammonia.

REVISION CHECK What should you be able to do? Recall and explain the physical properties of carboxylic acids Recall the structures of carboxylic acids, esters and acyl chlorides Recall the acidic properties of carboxylic acids Recall and explain the esterification of carboxylic acids Write balanced equations representing any reactions in the section Recall and explain the structure and naming of esters Recall the methods for making esters Recall the conditions for, and products of, the hydrolysis of esters. CAN YOU DO ALL OF THESE? YES NO

You need to go over the relevant topic(s) again Click on the button to return to the menu

WELL DONE! Try some past paper questions

© JONATHAN HOPTON & KNOCKHARDY PUBLISHING THE THE END AN INTRODUCTION TO CARBOXYLIC ACIDS AND THEIR DERIVATIVES