CONTENTS Structure of carboxylic acids Nomenclature Physical properties of carboxylic acids Preparation of carboxylic acids Chemical properties of carboxylic acids Esters CARBOXYLIC ACIDS

Before you start it would be helpful to… Recall the definition of a covalent bond Recall the difference types of physical bonding Be able to balance simple equations Be able to write out structures for simple organic molecules Understand the IUPAC nomenclature rules for simple organic compounds Recall the chemical properties of alkanes and alkenes CARBOXYLIC ACIDS

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

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 are isomeric with esters :- RCOOR’

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

INFRA-RED SPECTROSCOPY IDENTIFYING CARBOXYLIC ACIDS USING INFRA RED SPECTROSCOPY DifferentiationCompoundO-H C=O ALCOHOLYES NO CARBOXYLIC ACIDYES YES ESTER NO YES ALCOHOL CARBOXYLIC ACID ESTER O-H absorption O-H + C=O absorption C=O absorption

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 from the end nearer the COOH group as in alkanes, prefix with alkyl substituents side chain positions are based on the C in COOH being 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 from the end nearer the COOH group as in alkanes, prefix with alkyl substituents side chain positions are based on the C in COOH being 1 NAMING CARBOXYLIC ACIDS METHANOIC ACIDETHANOIC ACID PROPANOIC ACID

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 from the end nearer the COOH group as in alkanes, prefix with alkyl substituents side chain positions are based on the C in COOH being 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

101°C 118°C 141°C 164°C PHYSICAL PROPERTIES BOILING POINT Increases as size increases - due to increased van der Waals forces

Greater branching = lower inter-molecular forces = lower boiling point Boiling point is higher for “straight” chain isomers. 101°C 118°C 141°C 164°C 164°C 154°C PHYSICAL PROPERTIES BOILING POINT Increases as size increases - due to increased van der Waals forces

PHYSICAL PROPERTIES BOILING POINT Increases as size increases - due to increased van der Waals forces Carboxylic acids have high boiling points for their relative mass The effect of hydrogen bonding on the boiling point of compounds of similar mass CompoundFormulaM r b. pt. (°C)Comments ethanoic acidCH 3 COOH propan-1-olC 3 H 7 OH60 97 h-bonding propanalC 2 H 5 CHO58 49 dipole-dipole butaneC 4 H basic V der W

PHYSICAL PROPERTIES BOILING POINT Increases as size increases - due to increased van der Waals forces Carboxylic acids have high boiling points for their relative mass arises from inter-molecular hydrogen bonding due to polar O—H bonds AN EXTREME CASE... DIMERISATION extra inter-molecular attraction = more energy to separate molecules HYDROGEN BONDING

PHYSICAL PROPERTIES SOLUBILITY carboxylic acids are soluble in organic solvents they are also soluble in water due to hydrogen bonding HYDROGEN BONDING

PHYSICAL PROPERTIES SOLUBILITY carboxylic acids are soluble in organic solvents they are also soluble in water due to hydrogen bonding small ones dissolve readily in cold water as mass increases, the solubility decreases benzoic acid is fairly insoluble in cold but soluble in hot water HYDROGEN BONDING

CHEMICAL PROPERTIES ACIDITY weak acidsRCOOH + H 2 O (l) RCOO¯ (aq) + H 3 O + (aq) form saltsRCOOH + NaOH (aq) ——> RCOO¯Na + (aq) + H 2 O (l)

CHEMICAL PROPERTIES ACIDITY weak acidsRCOOH + H 2 O (l) RCOO¯ (aq) + H 3 O + (aq) form saltsRCOOH + NaOH (aq) ——> RCOO¯Na + (aq) + H 2 O (l) QUALITATIVE ANALYSIS Carboxylic acids are strong enough acids to liberate CO 2 from carbonates Phenols are also acidic but not are not strong enough to liberate 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 from ethanoic acid CH 3 COOCH 3 from methanol 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 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

PREPARATION OF ESTERS Reagent(s)alcohol + carboxylic acid Conditionsreflux with a strong acid catalyst (e.g. conc. H 2 SO 4 ) 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 For more details see under ‘Reactions of carboxylic acids’

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

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