CONTENTS Structure of carboxylic acids Nomenclature Physical properties of carboxylic acids Preparation of carboxylic acids Chemical properties of carboxylic acids Reduction of Carboxylic acids Esters Acyl chlorides and its reactions Triglycerides and fats Biofuels Polyester 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

Boiling temperature comparision Alcohol  london forces and Hydrogen bonding Halagenoalkane  C-F bonds stronger than C-C Aldehyde / Keytone/ester  permanent diplole – permanent dipole forces Alkenes  only london forces Carboxylic Acid  london forces and Hydrogen bonding (more london forces than alcohol as more Electrons in carboxylic acid Boiling Temp. No. of carbon atoms

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

PREPARATION OF CARBOXYLIC ACIDS Oxidation of aldehydesRCHO + [O] ——> RCOOH Hydrolysis of estersRCOOR + H 2 O RCOOH + ROH Hydrolysis of acyl chloridesRCOCl + H 2 O ——> RCOOH + HCl

Acid Hydrolysis of nitriles PREPARATION OF CARBOXYLIC ACIDS HY HYDROLISING NITRILES RCN —————————> RCOOH + NH 4 Cl Heat with dilute HCl (aq) RCN —————————> RCOOH + NH 4 Cl Base Hydrolysis of nitriles Heat with dilute NaOH (aq)  If you wanted the free carboxylic acid in this case, you would have to acidify the final solution with a strong acid such as dilute hydrochloric acid or dilute sulphuric acid. The ethanoate ion in the sodium ethanoate will react with hydrogen ions as mentioned above.

PREPARATION OF ESTERS - 1 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’

PREPARATION OF ESTERS - 2 Reagent(s)alcohol + acyl chloride Conditionsreflux under dry conditons Equation e.g. CH 3 OH (l) + CH 3 COCl (l) ——> CH 3 COOCH 3 (l) + HCl (g) methanol ethanoyl methyl chloride ethanoate NotesAcyl chlorides are very reactive but must be kept dry as they react with water.

PREPARATION OF ESTERS - 3 Reagent(s)alcohol + acid anhydride Conditionsreflux under dry conditons Equation e.g. CH 3 OH (l) + (CH 3 CO) 2 O (l) ——> CH 3 COOCH 3 (l) + CH 3 COOH (l) methanol ethanoic methyl ethanoic anhydride ethanoate acid NotesAcid 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.

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) 2RCOOH + Mg (s) ——> (RCOO¯) 2 Mg 2+ (aq) + H 2 (g)

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) 2RCOOH + Mg (s) ——> (RCOO¯) 2 Mg 2+ (aq) + H 2 (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.

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) 2RCOOH + Mg (s) ——> (RCOO¯) 2 Mg 2+ (aq) + H 2 (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 CO 2 from carbonates Phenols are also acidic but not are not strong enough to liberate CO 2.

REDUCTION Dry ether

CHLORINATION OF CARBOXYLIC ACIDS Chlorinationinvolves replacing the OH with a Cl Productacyl chloride Reagentthionyl chloride SOCl 2 ConditionsDRY conditions Equation CH 3 COOH + PCl 5 ——> CH 3 COCl + POCl 3 + HCl phosphorus(V) chloride Alternative CH 3 COOH + SOCl 2 ——> CH 3 COCl + SO 2 + HCl method

ACYL CHLORIDES  More reactive than carboxylic acid so using acyl chloride to make esters are faster

OTHER REACTIONS OF ACYL CHLORIDE

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 H 2 SO 4 Heat under reflux

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, acyl chlorides and acid anhydrides 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, acyl chlorides and acid anhydrides ReactivityUnreactive compared with acids and acyl chlorides IsomerismEsters are structural isomers of carboxylic acids ETHYL METHANOATE METHYL ETHANOATE

PHYSICAL PROPERTIES OF ESTER  Common esters such as ethyl ethanoate are volatile liquids And only slightly soluable in water  The reason for the solubility is that although esters can't hydrogen bond with themselves, they can hydrogen bond with water molecules.  As chain lengths increase, the hydrocarbon parts of the ester molecules start to get in the way. esterformula solubility (g per 100 g of water) ethyl methanoateHCOOCH 2 CH ethyl ethanoateCH 3 COOCH 2 CH ethyl propanoateCH 3 CH 2 COOCH 2 C H Soluability of esters

PHYSICAL PROPERTIES OF ESTER Boiling points of esters moleculetypeboiling point (°C) CH 3 COOCH 2 CH 3 ester77.1 CH 3 CH 2 CH 2 COOHcarboxylic acid164  The small esters have boiling points which are similar to those of aldehydes and ketones with the same number of carbon atoms.  Like aldehydes and ketones, they are polar molecules and so have dipole-dipole interactions as well as van der Waals dispersion forces. However, they don't form hydrogen bonds, and so their boiling points aren't anything like as high as an acid with the same number of carbon atoms. For example:

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 react with alcohols hydrolysed to acids STRUCTURAL ISOMERISM – FUNCTIONAL GROUP

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 2 CH 3 + H 2 O CH 3 COOH + CH 3 CH 2 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 2 CH 3 + H 2 O CH 3 COOH + CH 3 CH 2 OH alkaline CH 3 COOCH 2 CH 3 + NaOH ——> CH 3 COO¯ Na + + CH 3 CH 2 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 2 CH 3 + NaOH ——> CH 3 COO¯ Na + + CH 3 CH 2 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

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

TRIGLYCERIDES AND FATS Triglycerides are the most common component of edible fats and oils are triesters of the alcohol glycerol, (propane-1,2,3-triol) and fatty acids glycerol a triglyceride

TRIGLYCERIDES AND FATS Triglycerides are the most common component of edible fats and oils are triesters of the alcohol glycerol, (propane-1,2,3-triol) and fatty acidsSaponification 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 compounds the quality of a soap depends on the oils from which it is made

FATTY ACIDS Carboxylic acids that are obtained from natural oils and fats; they can be… Saturated SaturatedCH 3 (CH 2 ) 16 COOH octadecanoic acid (stearic acid)

FATTY ACIDS Carboxylic acids that are obtained from natural oils and fats; they can be… Saturated SaturatedCH 3 (CH 2 ) 16 COOH octadecanoic acid (stearic acid) 9 Unsaturated UnsaturatedCH 3 (CH 2 ) 7 CH=CH(CH 2 ) 7 COOHoctadec-9-enoic acid (oleic acid) cis (Z) isomer trans (E) isomer

FATTY ACIDS Carboxylic acids that are obtained from natural oils and fats; they can be… Saturated SaturatedCH 3 (CH 2 ) 16 COOH octadecanoic acid (stearic acid) 9 Unsaturated UnsaturatedCH 3 (CH 2 ) 7 CH=CH(CH 2 ) 7 COOHoctadec-9-enoic acid (oleic acid) cis (Z) isomer trans (E) isomer 12 9 CH 3 (CH 2 ) 4 CH=CHCH 2 CH=CH(CH 2 ) 7 COOH octadec-9,12-dienoic acid (linoleic acid)

FATTY ACIDS AND HEALTH Saturated Saturated solids at room temperature found in meat and dairy products are bad for health increase cholesterol levels - can lead to heart problems

FATTY ACIDS AND HEALTH Saturated Saturated solids at room temperature found in meat and dairy products are bad for health increase cholesterol levels - can lead to heart problems Mono unsaturated unsaturated contain just one C=C thought to be neutral to our health found in olives, olive oil, groundnut oil, nuts, avocados

FATTY ACIDS AND HEALTH Saturated Saturated solids at room temperature found in meat and dairy products are bad for health increase cholesterol levels - can lead to heart problems Mono unsaturated unsaturated contain just one C=C thought to be neutral to our health found in olives, olive oil, groundnut oil, nuts, avocadosPoly unsaturated unsaturated are considered to be ‘good fats’ contain more than one C=C bond tend to be liquids at room temperature, eg olive oil. can be split into two main types... Omega 3 - fatty acids Omega 6 - fatty acids

FATTY ACIDS AND HEALTH Saturated Saturated solids at room temperature found in meat and dairy products are bad for health increase cholesterol levels - can lead to heart problems Mono unsaturated unsaturated contain just one C=C thought to be neutral to our health found in olives, olive oil, groundnut oil, nuts, avocadosPoly unsaturated unsaturated are considered to be ‘good fats’ contain more than one C=C bond tend to be liquids at room temperature, eg olive oil. can be split into two main types... Omega 3 - fatty acids Omega 6 - fatty acids

OMEGA 3 and 6 FATTY ACIDS Omega 3 - fatty acids Omega 3 - fatty acidslower the total amount of fat in the blood and can lower blood pressure and decrease the risk of cardiovascular disease 3  (omega) endCH 3 CH 2 CH=CHCH 2 CH 2 CH 2 CH 2 CH=CH(CH 2 ) 7 COOH The omega numbering system starts from the opposite end to the carboxylic acid group

OMEGA 3 and 6 FATTY ACIDS Omega 3 - fatty acids Omega 3 - fatty acidslower the total amount of fat in the blood and can lower blood pressure and decrease the risk of cardiovascular disease 3  (omega) endCH 3 CH 2 CH=CHCH 2 CH 2 CH 2 CH 2 CH=CH(CH 2 ) 7 COOH Omega 6 - fatty acids Omega 6 - fatty acidsreduce the risk of cardiovascular disease but can contribute to allergies and inflammation 6  (omega) endCH 3 CH 2 CH 2 CH 2 CH 2 CH=CHCH 2 CH=CH(CH 2 ) 7 COOH

CHOLESTEROL a fatty substance which is found in the blood it is mainly made in the body plays an essential role in how every cell in the body works eating too much saturated fat increases cholesterol levels too much cholesterol in the blood can increase the risk of heart problems

CHOLESTEROL a fatty substance which is found in the blood it is mainly made in the body plays an essential role in how every cell in the body works eating too much saturated fat increases cholesterol levels too much cholesterol in the blood can increase the risk of heart problems Ways to reduce cholesterol levels cut down on saturated fats and trans fats (trans fats are more stable and difficult to break down in the body) replace them with monounsaturated fats and polyunsaturated fats eat oily fish have a high fibre diet; porridge, beans, fruit and vegetables exercise regularly

BIOFUELS What are they? Liquid fuels made from plant material and recycled elements of the food chainBiodiesel An alternative fuel which can be made from waste vegetable oil or from oil produced from seeds. It can be used in any diesel engine, either neat or mixed with petroleum diesel. It is a green fuel, does not contribute to the carbon dioxide (CO 2 ) burden and produces drastically reduced engine emissions. It is non-toxic and biodegradable. vegetable oilglycerolbiodiesel

BIOFUELS Advantages  Reuses/reduces waste (vegetable) oil/ lessens need to dispose of (vegetable) oil  Could lessen use of (non-renewable/nonsustainable) crude oil/fossil fuels  vegetable oil/biodiesel/reactants renewable/ sustainable  Plants grown for vegetable oil could offset some CO2 emissions

BIOFUELS Disadvantages Disadvantages poor availability - very few outlets & manufacturers more expensive to produce poorly made biodiesel can cause engine problems Future problems problems there isn’t enough food waste to produce large amounts crops grown for biodiesel use land for food crops a suitable climate is needed to grow most crops some countries have limited water resources

POLYESTER Polyesters are polymers in which the monomers are liked together by ester groups

POLYESTER

POLYESTER Hydrolysis of polyester Polymer + Acid  Hydrolysis/ Break down to monomers Simple esters are easily hydrolysed by reaction with dilute acids or alkalis.