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![PREPARATION OF CARBOXYLIC ACIDS
Oxidation of aldehydes RCHO + [O] ——> RCOOH
Hydrolysis of esters RCOOR + H2O RCOOH + ROH
Hydrolysis of acyl chlorides RCOCl + H2O ——> RCOOH + HCl
Hydrolysis of nitriles RCN + 2 H2O ——> RCOOH + NH3
Hydrolysis of amides RCONH2 + H2O ——> RCOOH + NH3](https://image.slidesharecdn.com/carboxylicacidsandacylcompounds-250805044102-a08c19e1/75/Carboxylic-acids-and-acyl-compounds-pptx-20-2048.jpg)
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Carboxylic acids and acyl compounds.pptx
- 1. AN INTRODUCTION TO CARBOXYLICACIDS AND THEIR DERIVATIVES
- 2. CONTENTS • Structure ofcarboxylic acids • Nomenclature • Physical properties of carboxylic acids • Preparation of carboxylic acids • Chemical properties of carboxylic acids • Acyl chlorides • Esters • Triglycerides and fats • Biofuels CARBOXYLIC ACIDS
- 3. Before you startit 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
- 4. STRUCTURE OF CARBOXYLICACIDS • contain the carboxyl functional group COOH • the bonds are in a planar arrangement
- 5. STRUCTURE OF CARBOXYLICACIDS • 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
- 6. STRUCTURE OF CARBOXYLICACIDS • 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’
- 7. HOMOLOGOUS SERIES HCOOH CH3COOHC2H5COOH Carboxylic acids form a homologous series
- 8. Carboxylic acids forma homologous series HOMOLOGOUS SERIES HCOOH CH3COOH C2H5COOH With more carbon atoms, there can be structural isomers C3H7COOH (CH3)2CHCOOH
- 9. INFRA-RED SPECTROSCOPY IDENTIFYING CARBOXYLICACIDS USING INFRA RED SPECTROSCOPY Differentiation Compound O-H C=O ALCOHOL YES NO CARBOXYLIC ACID YES YES ESTER NO YES ALCOHOL CARBOXYLIC ACID ESTER O-H absorption O-H + C=O absorption C=O absorption
- 10. Acids are namedaccording 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. CH3 - CH(CH3) - CH2 - CH2 - COOH is called 4-methylpentanoic acid NAMING CARBOXYLIC ACIDS
- 11. Acids are namedaccording 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 ACID ETHANOIC ACID PROPANOIC ACID
- 12. Acids are namedaccording 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 ACID 2-METHYLPROPANOIC ACID
- 13. NAMING CARBOXYLIC ACIDS Acidsare 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. Formula Systematic name (trivial name) origin of name HCOOH methanoic acid formic acid latin for ant CH3COOH ethanoic acid acetic acid latin for vinegar C6H5COOH benzenecarboxylic acid benzoic acid from benzene
- 14. 101°C 118°C 141°C164°C PHYSICAL PROPERTIES BOILING POINT Increases as size increases - higher induced dipole-dipole interactions
- 15. 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 - higher induced dipole-dipole interactions
- 16. PHYSICAL PROPERTIES BOILING POINT Increasesas size increases - higher induced dipole-dipole interactions Carboxylic acids have high boiling points for their relative mass The effect of hydrogen bonding on the boiling point of compounds of similar mass Compound Formula Mr b. pt. (°C) Comments ethanoic acid CH3COOH 60 118 + h-bonding propan-1-ol C3H7OH 60 97 + h-bonding propanal C2H5CHO 58 49 + permanent dipole-dipole butane C4H10 58 - 0.5 induced dipole-dipole
- 17. PHYSICAL PROPERTIES BOILING POINT Increasesas size increases - higher induced dipole-dipole interactions 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
- 18. PHYSICAL PROPERTIES SOLUBILITY • carboxylicacids are soluble in organic solvents • they are also soluble in water due to hydrogen bonding HYDROGEN BONDING
- 19. PHYSICAL PROPERTIES SOLUBILITY • carboxylicacids 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
- 20. PREPARATION OF CARBOXYLICACIDS Oxidation of aldehydes RCHO + [O] ——> RCOOH Hydrolysis of esters RCOOR + H2O RCOOH + ROH Hydrolysis of acyl chlorides RCOCl + H2O ——> RCOOH + HCl Hydrolysis of nitriles RCN + 2 H2O ——> RCOOH + NH3 Hydrolysis of amides RCONH2 + H2O ——> RCOOH + NH3
- 21. CHEMICAL PROPERTIES ACIDITY weak acidsRCOOH + H2O(l) RCOO¯(aq) + H3O+ (aq) form salts RCOOH + NaOH(aq) ——> RCOO¯Na+ (aq) + H2O(l) 2RCOOH + Mg(s) ——> (RCOO¯)2Mg2+ (aq) + H2(g)
- 22. CHEMICAL PROPERTIES ACIDITY weak acidsRCOOH + H2O(l) RCOO¯(aq) + H3O+ (aq) form salts RCOOH + NaOH(aq) ——> RCOO¯Na+ (aq) + H2O(l) 2RCOOH + Mg(s) ——> (RCOO¯)2Mg2+ (aq) + H2(g) The acid can be liberated from its salt by treatment with a stronger acid. e.g. RCOO¯ Na+ (aq) + HCl(aq) ——> RCOOH + NaCl(aq) Conversion of an acid to its water soluble salt followed by acidification of the salt to restore the acid is often used to separate acids from a mixture.
- 23. CHEMICAL PROPERTIES ACIDITY weak acidsRCOOH + H2O(l) RCOO¯(aq) + H3O+ (aq) form salts RCOOH + NaOH(aq) ——> RCOO¯Na+ (aq) + H2O(l) 2RCOOH + Mg(s) ——> (RCOO¯)2Mg2+ (aq) + H2(g) The acid can be liberated from its salt by treatment with a stronger acid. e.g. RCOO¯ Na+ (aq) + HCl(aq) ——> RCOOH + NaCl(aq) Conversion of an acid to its water soluble salt followed by acidification of the salt to restore the acid is often used to separate acids from a mixture. QUALITATIVE ANALYSIS Carboxylic acids are strong enough acids to liberate CO2 from carbonates Phenols are also acidic but not are not strong enough to liberate CO2.
- 24. ESTERIFICATION Reagent(s) alcohol +strong acid catalyst (e.g. conc. H2SO4 ) Conditions reflux Product ester Equation e.g. CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate
- 25. ESTERIFICATION Reagent(s) alcohol +strong acid catalyst (e.g. conc. H2SO4 ) Conditions reflux Product ester Equation e.g. CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate Notes Conc. H2SO4 is a dehydrating agent - it removes water causing the equilibrium to move to the right and thus increases the yield of the ester
- 26. ESTERIFICATION Reagent(s) alcohol +strong acid catalyst (e.g conc. H2SO4 ) Conditions reflux Product ester Equation e.g. CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate Notes Conc. H2SO4 is a dehydrating agent - it removes water causing the equilibrium to move to the right and thus increases the yield of the ester Naming esters Named from the original alcohol and carboxylic acid CH3OH + CH3COOH CH3COOCH3 + H2O from ethanoic acid CH3COOCH3 from methanol METHYL ETHANOATE
- 27. CHLORINATION OF CARBOXYLICACIDS Chlorination involves replacing the OH with a Cl Product acyl chloride Reagent thionyl chloride SOCl2 Conditions DRY conditions Equation CH3COOH + SOCl2 ——> CH3COCl + SO2 + HCl Alternative method CH3COOH + PCl5 ——> CH3COCl + POCl3 + HCl phosphorus(V) chloride
- 28. ACYL CHLORIDES Structure Replacethe OH of a carboxylic acid with a Cl atom Nomenclature Named from corresponding acid … remove -ic add -yl chloride CH3COCl ethanoyl (acetyl) chloride C6H5COCl benzene carbonyl (benzoyl) chloride ETHANOYL CHLORIDE
- 29. ACYL CHLORIDES -PROPERTIES Physical • polar, colourless liquids which fume in moist air d+ d- d-
- 30. ACYL CHLORIDES -PROPERTIES Physical • polar, colourless liquids which fume in moist air Chemical • attacked at the positive carbon centre by nucleophiles such as water, alcohols, ammonia and amines • undergo addition-elimination reactions • MUCH MORE REACTIVE THAN… CARBOXYLIC ACIDS AND ACID ANHYDRIDES d+ d- d-
- 31. ACYL CHLORIDES -REACTIONS WATER Product(s) carboxylic acid + HCl (fume in moist air / strong acidic solution formed) Conditions cold water Equation CH3COCl(l) + H2O(l) —> CH3COOH(aq) + HCl(aq) Mechanism addition-elimination
- 32. ACYL CHLORIDES -REACTIONS WATER Product(s) carboxylic acid + HCl (fume in moist air / strong acidic solution formed) Conditions cold water Equation CH3COCl(l) + H2O(l) —> CH3COOH(aq) + HCl(aq) Mechanism addition-elimination ALCOHOLS Product(s) ester + hydrogen chloride Conditions reflux in dry (anhydrous) conditions Equation CH3COCl(l) + CH3OH(l) —> CH3COOCH3(l) + HCl(g) Mechanism addition-elimination
- 33. ACYL CHLORIDES -REACTIONS AMMONIA Product(s) Amide + hydrogen chloride Conditions Low temperature and excess ammonia. Vigorous reaction. Equation CH3COCl(l) + NH3(aq) —> CH3CONH2(s) + HCl(g) or CH3COCl(l) + 2NH3(aq) —> CH3CONH2(s) + NH4Cl(s) Mechanism addition-elimination
- 34. ACYL CHLORIDES -REACTIONS AMMONIA Product(s) Amide + hydrogen chloride Conditions Low temperature and excess ammonia. Vigorous reaction. Equation CH3COCl(l) + NH3(aq) —> CH3CONH2(s) + HCl(g) or CH3COCl(l) + 2NH3(aq) —> CH3CONH2(s) + NH4Cl(s) Mechanism addition-elimination AMINES Product(s) N-substituted amide + hydrogen chloride Conditions anhydrous Equation CH3COCl(l) + C2H5NH2(aq) —> CH3CONHC2H5(s) + HCl(g) or CH3COCl(l) + 2C2H5NH2(aq) —> CH3CONHC2H5(l) + C2H5NH3Cl(s) Mechanism addition-elimination
- 35. ESTERS Structure Substitute anorganic group for the H in carboxylic acids Nomenclature first part from alcohol, second part from acid e.g. methyl ethanoate CH3COOCH3 ETHYL METHANOATE METHYL ETHANOATE
- 36. ESTERS Structure Substitute anorganic group for the H in carboxylic acids Nomenclature first part from alcohol, second part from acid e.g. methyl ethanoate CH3COOCH3 Preparation From carboxylic acids, acyl chlorides and acid anhydrides Reactivity Unreactive compared with acids and acyl chlorides ETHYL METHANOATE METHYL ETHANOATE
- 37. ESTERS Structure Substitute anorganic group for the H in carboxylic acids Nomenclature first part from alcohol, second part from acid e.g. methyl ethanoate CH3COOCH3 Preparation From carboxylic acids, acyl chlorides and acid anhydrides Reactivity Unreactive compared with acids and acyl chlorides Isomerism Esters are structural isomers of carboxylic acids ETHYL METHANOATE METHYL ETHANOATE
- 38. Classification CARBOXYLIC ACIDESTER Functional Group R-COOH R-COOR Name PROPANOIC ACID METHYL ETHANOATE Physical properties O-H bond gives rise No hydrogen bonding to hydrogen bonding; insoluble in water get higher boiling point and solubility in water Chemical properties acidic fairly unreactive react with alcohols hydrolysed to acids STRUCTURAL ISOMERISM – FUNCTIONAL GROUP
- 39. PREPARATION OF ESTERS- 1 Reagent(s) alcohol + carboxylic acid Conditions reflux with a strong acid catalyst (e.g. conc. H2SO4 ) Equation e.g. CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate Notes Conc. H2SO4 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’
- 40. PREPARATION OF ESTERS- 2 Reagent(s) alcohol + acyl chloride Conditions reflux under dry conditons Equation e.g. CH3OH(l) + CH3COCl(l) ——> CH3COOCH3(l) + HCl(g) methanol ethanoyl methyl chloride ethanoate Notes Acyl chlorides are very reactive but must be kept dry as they react with water.
- 41. PREPARATION OF ESTERS- 3 Reagent(s) alcohol + acid anhydride Conditions reflux under dry conditons Equation e.g. CH3OH(l) + (CH3CO)2O(l) ——> CH3COOCH3(l) + CH3COOH(l) methanol ethanoic methyl ethanoic anhydride ethanoate acid Notes Acid anhydrides are not as reactive as acyl chlorides so the the reaction is slower. The reaction is safer - it is less exothermic. Acid anhydrides are less toxic.
- 42. HYDROLYSIS OF ESTERS Hydrolysisis the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C2H5OH METHANOIC ETHANOL ACID ETHYL METHANOATE
- 43. HYDROLYSIS OF ESTERS Hydrolysisis the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C2H5OH METHANOIC ETHANOL ACID ETHYL METHANOATE METHYL ETHANOATE
- 44. HYDROLYSIS OF ESTERS Hydrolysisis the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C2H5OH METHANOIC ETHANOL ACID CH3COOH + CH3OH ETHANOIC METHANOL ACID ETHYL METHANOATE METHYL ETHANOATE
- 45. HYDROLYSIS OF ESTERS Hydrolysisis the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL The products of hydrolysis depend on the conditions used... acidic CH3COOCH3 + H2O CH3COOH + CH3OH alkaline CH3COOCH3 + NaOH ——> CH3COO¯ Na+ + CH3OH
- 46. HYDROLYSIS OF ESTERS Hydrolysisis the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL The products of hydrolysis depend on the conditions used... acidic CH3COOCH3 + H2O CH3COOH + CH3OH alkaline CH3COOCH3 + NaOH ——> CH3COO¯ Na+ + CH3OH
- 47. HYDROLYSIS OF ESTERS Hydrolysisis the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL The products of hydrolysis depend on the conditions used... acidic CH3COOCH3 + H2O CH3COOH + CH3OH alkaline CH3COOCH3 + NaOH ——> CH3COO¯ Na+ + CH3OH If the hydrolysis takes place under alkaline conditions, the organic product is a water soluble ionic salt
- 48. HYDROLYSIS OF ESTERS Hydrolysisis the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL The products of hydrolysis depend on the conditions used... acidic CH3COOCH3 + H2O CH3COOH + CH3OH alkaline CH3COOCH3 + NaOH ——> CH3COO¯ Na+ + CH3OH 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 CH3COO¯ Na+ + HCl ——> CH3COOH + NaCl
- 49. USES OF ESTERS Despitebeing fairly chemically unreactive, esters are useful as ... • flavourings apple 2-methylbutanoate pear 3-methylbutylethanoate banana 1-methylbutylethanoate pineapple butylbutanoate rum 2-methylpropylpropanoate • solvents nail varnish remover - ethyl ethanoate • plasticisers
- 50. THE END AN INTRODUCTIONTO CARBOXYLIC ACIDS AND THEIR DERIVATIVES