1 / 36

CONTENTS Structure of carboxylic acids Nomenclature

CARBOXYLIC ACIDS. 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…

patty
Télécharger la présentation

CONTENTS Structure of carboxylic acids Nomenclature

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. 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

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

  4. 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

  5. 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’

  6. HOMOLOGOUS SERIES Carboxylic acids form a homologous series HCOOHCH3COOH C2H5COOH

  7. HOMOLOGOUS SERIES Carboxylic acids form a homologous series HCOOHCH3COOH C2H5COOH With more carbon atoms, there can be structural isomers C3H7COOH (CH3)2CHCOOH

  8. INFRA-RED SPECTROSCOPY IDENTIFYING CARBOXYLIC ACIDS USING INFRA RED SPECTROSCOPY DifferentiationCompound O-H C=O ALCOHOLYESNO CARBOXYLIC ACIDYESYES ESTERNOYES ALCOHOL CARBOXYLIC ACID ESTER O-H absorption O-H + C=O absorption C=O absorption

  9. 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 e.g. CH3 - CH(CH3) - CH2 - CH2 - COOH is called 4-methylpentanoic acid

  10. 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 METHANOIC ACID ETHANOIC ACID PROPANOIC ACID

  11. 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 BUTANOIC ACID 2-METHYLPROPANOIC ACID

  12. 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. 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

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

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

  15. 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 Compound Formula Mr b. pt. (°C) Comments ethanoic acid CH3COOH 60 118 propan-1-ol C3H7OH 60 97 h-bonding propanal C2H5CHO 58 49 dipole-dipole butane C4H10 58 - 0.5 basic V der W

  16. HYDROGEN BONDING 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

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

  18. 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

  19. CHEMICAL PROPERTIES ACIDITY weak acids RCOOH + H2O(l) RCOO¯(aq) + H3O+(aq) form salts RCOOH + NaOH(aq) ——> RCOO¯Na+(aq) + H2O(l)

  20. CHEMICAL PROPERTIES ACIDITY weak acids RCOOH + H2O(l) RCOO¯(aq) + H3O+(aq) form salts RCOOH + NaOH(aq) ——> RCOO¯Na+(aq) + H2O(l) 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

  21. ESTERIFICATION Reagent(s) alcohol + strong acid catalyst (e.g. conc. H2SO4 ) Conditions reflux Product ester Equatione.g. CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate

  22. ESTERIFICATION Reagent(s) alcohol + strong acid catalyst (e.g. conc. H2SO4 ) Conditions reflux Product ester Equatione.g. CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate NotesConc.H2SO4 is a dehydrating agent - it removes water causing the equilibrium to move to the right and thus increases the yield of the ester

  23. 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 + CH3COOHCH3COOCH3+ H2O fromethanoic acidCH3COOCH3from methanol METHYLETHANOATE

  24. ESTERS Structure Substitute an organic group for the H in carboxylic acids Nomenclature first part from alcohol, second part from acid e.g. methyl ethanoate CH3COOCH3 METHYL ETHANOATE ETHYL METHANOATE

  25. ESTERS Structure Substitute an organic 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 or acyl chlorides Reactivity Unreactive compared with acids and acyl chlorides METHYL ETHANOATE ETHYL METHANOATE

  26. ESTERS Structure Substitute an organic 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 or acyl chlorides Reactivity Unreactive compared with acids and acyl chlorides Isomerism Esters are structural isomers of carboxylic acids METHYL ETHANOATE ETHYL METHANOATE

  27. STRUCTURAL ISOMERISM – FUNCTIONAL GROUP ClassificationCARBOXYLIC ACIDESTER Functional GroupR-COOHR-COOR NamePROPANOIC 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 properties acidic fairly unreactive reacts with alcohols hydrolysed to acids

  28. PREPARATION OF ESTERS Reagent(s) alcohol + carboxylic acid Conditions reflux with a strong acid catalyst (e.g. conc. H2SO4 ) Equatione.g. CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate NotesConc.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’

  29. HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C2H5OH METHANOIC ETHANOL ACID ETHYL METHANOATE

  30. HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C2H5OH METHANOIC ETHANOL ACID ETHYL METHANOATE METHYL ETHANOATE

  31. HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification ESTER + WATER CARBOXYLIC ACID + ALCOHOL HCOOH + C2H5OH METHANOIC ETHANOL ACID ETHYL METHANOATE CH3COOH + CH3OH ETHANOIC METHANOL ACID METHYL ETHANOATE

  32. HYDROLYSIS OF ESTERS Hydrolysis is 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

  33. HYDROLYSIS OF ESTERS Hydrolysis is 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

  34. HYDROLYSIS OF ESTERS Hydrolysis is 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

  35. CH2OH CHOH CH2OH 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

  36. USES OF ESTERS Despite being 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

More Related