AN INTRODUCTION TOCARBOXYLIC ACIDS AND THEIR .ppt

1、AN INTRODUCTION TO CARBOXYLIC ACIDS AND THEIR DERIVATIVES,KNOCKHARDY PUBLISHING,2015 SPECIFICATIONS,INTRODUCTION This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications

2、 but is suitable for other examination boards. Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available. Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKH

3、ARDY SCIENCE WEBSITE at. www.knockhardy.org.uk/sci.htmNavigation is achieved by. either clicking on the grey arrows at the foot of each pageor using the left and right arrow keys on the keyboard,KNOCKHARDY PUBLISHING,CARBOXYLIC ACIDS,CONTENTSStructure of carboxylic acids NomenclaturePhysical propert

4、ies of carboxylic acidsPreparation of carboxylic acidsChemical properties of carboxylic acidsAcyl chloridesEstersTriglycerides and fatsBiofuels,CARBOXYLIC ACIDS,Before you start it would be helpful toRecall the definition of a covalent bondRecall the difference types of physical bondingBe able to ba

5、lance simple equationsBe able to write out structures for simple organic moleculesUnderstand the IUPAC nomenclature rules for simple organic compoundsRecall the chemical properties of alkanes and alkenes,CARBOXYLIC ACIDS,STRUCTURE OF CARBOXYLIC ACIDS, contain the carboxyl functional group COOH the b

6、onds 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 anda hydroxyl (O-H) group,STRUCTURE OF CARBOXYLIC ACIDS, contain the carboxyl functional group COOH the bonds are in a plana

7、r arrangement include a carbonyl (C=O) group anda hydroxyl (O-H) group are isomeric with esters :- RCOOR,HOMOLOGOUS SERIES,HCOOH CH3COOH C2H5COOH,Carboxylic acids form a homologous series,Carboxylic acids form a homologous series,HOMOLOGOUS SERIES,HCOOH CH3COOH C2H5COOH,With more carbon atoms, there

8、 can be structural isomers,C3H7COOH (CH3)2CHCOOH,INFRA-RED SPECTROSCOPY,IDENTIFYING CARBOXYLIC ACIDS USING INFRA RED SPECTROSCOPYDifferentiation Compound O-H C=OALCOHOL YES NOCARBOXYLIC ACID YES YESESTER NO YESALCOHOL CARBOXYLIC ACID ESTERO-H absorption O-H + C=O absorption C=O absorption,Acids are

9、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

10、 in COOH being 1e.g. CH3 - CH(CH3) - CH2 - CH2 - 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

11、 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,Acids are named according to standard IUPAC rules select the longest chain of C atoms containi

12、ng 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,NAMING

13、 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 fo

14、r ant CH3COOH ethanoic acid acetic acid latin for vinegar C6H5COOH benzenecarboxylic acid benzoic acid from benzene,101C 118C 141C 164C,PHYSICAL PROPERTIES,BOILING POINTIncreases as size increases - higher induced dipole-dipole interactions,Greater branching = lower inter-molecular forces = lower bo

15、iling point,Boiling point is higher for “straight” chain isomers.,101C 118C 141C 164C,164C 154C,PHYSICAL PROPERTIES,BOILING POINTIncreases as size increases - higher induced dipole-dipole interactions,PHYSICAL PROPERTIES,BOILING POINTIncreases as size increases - higher induced dipole-dipole interac

16、tionsCarboxylic acids have high boiling points for their relative massThe effect of hydrogen bonding on the boiling point of compounds of similar massCompound 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 + permane

17、nt dipole-dipole butane C4H10 58 - 0.5 induced dipole-dipole,PHYSICAL PROPERTIES,BOILING POINTIncreases as size increases - higher induced dipole-dipole interactionsCarboxylic acids have high boiling points for their relative mass arises from inter-molecular hydrogen bonding due to polar OH bondsAN

18、EXTREME CASE. DIMERISATION extra inter-molecular attraction = more energy to separate molecules,PHYSICAL PROPERTIES,SOLUBILITY carboxylic acids are soluble in organic solvents they are also soluble in water due to hydrogen bonding,PHYSICAL PROPERTIES,SOLUBILITY carboxylic acids are soluble in organi

19、c 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,PREPARATION OF CARBOXYLIC ACIDS,Oxidation of aldehydes RCHO + O RCOOH Hydrolysis o

20、f esters RCOOR + H2O RCOOH + ROHHydrolysis of acyl chlorides RCOCl + H2O RCOOH + HClHydrolysis of nitriles RCN + 2 H2O RCOOH + NH3Hydrolysis of amides RCONH2 + H2O RCOOH + NH3,CHEMICAL PROPERTIES,ACIDITYweak acids RCOOH + H2O(l) RCOO(aq) + H3O+(aq)form salts RCOOH + NaOH(aq) RCOONa+(aq) + H2O(l)2RCO

21、OH + Mg(s) (RCOO)2Mg2+(aq) + H2(g),CHEMICAL PROPERTIES,ACIDITYweak acids RCOOH + H2O(l) RCOO(aq) + H3O+(aq)form salts RCOOH + NaOH(aq) RCOONa+(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

22、 + 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.,CHEMICAL PROPERTIES,ACIDITYweak acids RCOOH + H2O(l) RCOO(aq) + H3O+(aq)form salts RCOOH + NaOH(aq) RCOONa+(aq) + H2O(l)2RCOOH + Mg(s)

23、(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.QUALIT

24、ATIVE 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.,ESTERIFICATION,Reagent(s) alcohol + strong acid catalyst (e.g. conc. H2SO4 ) Conditions reflux Product ester Equation e.g. CH3CH2OH(l) + CH3C

25、OOH(l) CH3COOC2H5(l) + H2O(l)ethanol ethanoic acid ethyl ethanoate,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 ethanoateNotes Conc. H2SO4 is a deh

26、ydrating agent - it removes watercausing the equilibrium to move to the right and thusincreases the yield of the ester,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 etha

27、noic acid ethyl ethanoateNotes Conc. H2SO4 is a dehydrating agent - it removes watercausing the equilibrium to move to the right and thusincreases the yield of the esterNaming esters Named from the original alcohol and carboxylic acidCH3OH + CH3COOH CH3COOCH3 + H2Ofrom ethanoic acid CH3COOCH3 from m

28、ethanolMETHYL ETHANOATE,CHLORINATION OF CARBOXYLIC ACIDS,Chlorination involves replacing the OH with a Cl Product acyl chlorideReagent thionyl chloride SOCl2Conditions DRY conditionsEquation CH3COOH + SOCl2 CH3COCl + SO2 + HClAlternative method CH3COOH + PCl5 CH3COCl + POCl3 + HClphosphorus(V) chlor

29、ide,ACYL CHLORIDES,Structure Replace the OH of a carboxylic acid with a Cl atomNomenclature Named from corresponding acid remove -ic add -yl chlorideCH3COCl ethanoyl (acetyl) chlorideC6H5COCl benzene carbonyl (benzoyl) chloride,ETHANOYL CHLORIDE,ACYL CHLORIDES - PROPERTIES,Physical polar, colourless

30、 liquids which fume in moist air,d+,d-,d-,ACYL CHLORIDES - PROPERTIES,Physical polar, colourless liquids which fume in moist airChemical attacked at the positive carbon centre by nucleophilessuch as water, alcohols, ammonia and amines undergo addition-elimination reactions MUCH MORE REACTIVE THANCAR

31、BOXYLIC ACIDS AND ACID ANHYDRIDES,d+,d-,d-,ACYL CHLORIDES - REACTIONS,WATERProduct(s) carboxylic acid + HCl (fume in moist air / strongacidic solution formed) Conditions cold water Equation CH3COCl(l) + H2O(l) CH3COOH(aq) + HCl(aq)Mechanism addition-elimination,ACYL CHLORIDES - REACTIONS,WATERProduc

32、t(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-eliminationALCOHOLSProduct(s) ester + hydrogen chlorideConditions reflux in dry (anhydrous) conditions Equation CH3COCl(l) + CH3OH(

33、l) CH3COOCH3(l) + HCl(g)Mechanism addition-elimination,ACYL CHLORIDES - REACTIONS,AMMONIAProduct(s) Amide + hydrogen chlorideConditions 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 add

34、ition-elimination,ACYL CHLORIDES - REACTIONS,AMMONIAProduct(s) Amide + hydrogen chlorideConditions 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-eliminationAMINESProduct(s) N-s

35、ubstituted amide + hydrogen chlorideConditions anhydrous Equation CH3COCl(l) + C2H5NH2(aq) CH3CONHC2H5(s) + HCl(g)or CH3COCl(l) + 2C2H5NH2(aq) CH3CONHC2H5(l) + C2H5NH3Cl(s)Mechanism addition-elimination,ESTERS,Structure Substitute an organic group for the H in carboxylic acidsNomenclature first part

36、 from alcohol, second part from acide.g. methyl ethanoate CH3COOCH3,ETHYL METHANOATE,METHYL ETHANOATE,ESTERS,Structure Substitute an organic group for the H in carboxylic acidsNomenclature first part from alcohol, second part from acide.g. methyl ethanoate CH3COOCH3Preparation From carboxylic acids,

37、 acyl chlorides and acid anhydridesReactivity Unreactive compared with acids and acyl chlorides,ETHYL METHANOATE,METHYL ETHANOATE,ESTERS,Structure Substitute an organic group for the H in carboxylic acidsNomenclature first part from alcohol, second part from acide.g. methyl ethanoate CH3COOCH3Prepar

38、ation From carboxylic acids, acyl chlorides and acid anhydridesReactivity Unreactive compared with acids and acyl chloridesIsomerism Esters are structural isomers of carboxylic acids,ETHYL METHANOATE,METHYL ETHANOATE,Classification CARBOXYLIC ACID ESTERFunctional Group R-COOH R-COORName PROPANOIC AC

39、ID METHYL ETHANOATEPhysical properties O-H bond gives rise No hydrogen bondingto hydrogen bonding; insoluble in waterget higher boiling pointand solubility in water Chemical properties acidic fairly unreactivereact with alcohols hydrolysed to acids,STRUCTURAL ISOMERISM FUNCTIONAL GROUP,PREPARATION O

40、F ESTERS - 1,Reagent(s) alcohol + carboxylic acidConditions 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 ethanoateNotes Conc. H2SO4 is a dehydrating agent - it removes watercausing the equilibrium to mo

41、ve to the right and thusincreases the yield of the esterFor more details see under Reactions of carboxylic acids,PREPARATION OF ESTERS - 2,Reagent(s) alcohol + acyl chlorideConditions reflux under dry conditonsEquation e.g. CH3OH(l) + CH3COCl(l) CH3COOCH3(l) + HCl(g)methanol ethanoyl methyl chloride

42、 ethanoateNotes Acyl chlorides are very reactivebut must be kept dry as they reactwith water.,PREPARATION OF ESTERS - 3,Reagent(s) alcohol + acid anhydrideConditions reflux under dry conditonsEquation e.g. CH3OH(l) + (CH3CO)2O(l) CH3COOCH3(l) + CH3COOH(l)methanol ethanoic methyl ethanoicanhydride et

43、hanoate acidNotes Acid anhydrides are not as reactive asacyl chlorides so the the reaction is slower.The reaction is safer - it is less exothermic.Acid anhydrides are less toxic.,HYDROLYSIS OF ESTERS,Hydrolysis is the opposite of esterificationESTER + WATER CARBOXYLIC ACID + ALCOHOL,HCOOH + C2H5OH M

44、ETHANOIC ETHANOLACID,ETHYL METHANOATE,HYDROLYSIS OF ESTERS,Hydrolysis is the opposite of esterificationESTER + WATER CARBOXYLIC ACID + ALCOHOL,HCOOH + C2H5OH METHANOIC ETHANOLACID,ETHYL METHANOATE,METHYL ETHANOATE,HYDROLYSIS OF ESTERS,Hydrolysis is the opposite of esterificationESTER + WATER CARBOXY

45、LIC ACID + ALCOHOL,HCOOH + C2H5OH METHANOIC ETHANOLACID,CH3COOH + CH3OH ETHANOIC METHANOLACID,ETHYL METHANOATE,METHYL ETHANOATE,HYDROLYSIS OF ESTERS,Hydrolysis is the opposite of esterificationESTER + WATER CARBOXYLIC ACID + ALCOHOLThe products of hydrolysis depend on the conditions used.acidic CH3C

46、OOCH3 + H2O CH3COOH + CH3OHalkaline CH3COOCH3 + NaOH CH3COO Na+ + CH3OH,HYDROLYSIS OF ESTERS,Hydrolysis is the opposite of esterificationESTER + WATER CARBOXYLIC ACID + ALCOHOLThe products of hydrolysis depend on the conditions used.acidic CH3COOCH3 + H2O CH3COOH + CH3OHalkaline CH3COOCH3 + NaOH CH3

47、COO Na+ + CH3OH,HYDROLYSIS OF ESTERS,Hydrolysis is the opposite of esterificationESTER + WATER CARBOXYLIC ACID + ALCOHOLThe products of hydrolysis depend on the conditions used.acidic CH3COOCH3 + H2O CH3COOH + CH3OHalkaline CH3COOCH3 + NaOH CH3COO Na+ + CH3OHIf the hydrolysis takes place under alkaline conditions,the organic product is a water soluble ionic salt,