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AN INTRODUCTION TO CARBOXYLIC ACIDS AND THEIR DERIVATIVES. 2008 SPECIFICATIONS. KNOCKHARDY PUBLISHING. KNOCKHARDY PUBLISHING. CARBOXYLIC ACIDS. INTRODUCTION

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slide1

AN INTRODUCTION TO

CARBOXYLIC ACIDS AND THEIR DERIVATIVES

2008 SPECIFICATIONS

KNOCKHARDY PUBLISHING

slide2

KNOCKHARDY PUBLISHING

CARBOXYLIC ACIDS

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 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 KNOCKHARDY SCIENCE WEBSITE at...

www.knockhardy.org.uk/sci.htm

Navigation is achieved by...

either clicking on the grey arrows at the foot of each page

or using the left and right arrow keys on the keyboard

slide3

CARBOXYLIC ACIDS

  • CONTENTS
  • Structure of carboxylic acids
  • Nomenclature
  • Physical properties of carboxylic acids
  • Preparation of carboxylic acids
  • Chemical properties of carboxylic acids
  • Esters
  • Triglycerides and fats
  • Biofuels
slide4

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
slide5

STRUCTURE OF CARBOXYLIC ACIDS

• contain the carboxyl functional group COOH

• the bonds are in a planar arrangement

slide6

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

slide7

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’

slide8

HOMOLOGOUS SERIES

Carboxylic acids form a homologous series

HCOOHCH3COOH C2H5COOH

slide9

HOMOLOGOUS SERIES

Carboxylic acids form a homologous series

HCOOHCH3COOH C2H5COOH

With more carbon atoms, there can be structural isomers

C3H7COOH (CH3)2CHCOOH

slide10

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

slide11

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

slide12

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

slide13

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

slide14

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

slide15

PHYSICAL PROPERTIES

BOILING POINT

Increases as size increases - due to increased van der Waals forces

101°C 118°C 141°C 164°C

slide16

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

slide17

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

slide18

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

slide19

HYDROGEN BONDING

PHYSICAL PROPERTIES

SOLUBILITY

• carboxylic acids are soluble in organic solvents

• they are also soluble in water due to hydrogen bonding

slide20

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

slide21

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

slide22

CHEMICAL PROPERTIES

ACIDITY

weak acids RCOOH + H2O(l) RCOO¯(aq) + H3O+(aq)

form salts RCOOH + NaOH(aq) ——> RCOO¯Na+(aq) + H2O(l)

2RCOOH + Mg(s) ——> (RCOO¯)2Mg2+(aq) + H2(g)

slide23

CHEMICAL PROPERTIES

ACIDITY

weak acids RCOOH + 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.

slide24

CHEMICAL PROPERTIES

ACIDITY

weak acids RCOOH + 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.

slide25

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

slide26

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

slide27

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

slide28

CHLORINATION OF CARBOXYLIC ACIDS

Chlorination involves replacing the OH with a Cl

Product acyl chloride

Reagent thionyl chloride SOCl2

Conditions DRY conditions

EquationCH3COOH + SOCl2 ——> CH3COCl + SO2 + HCl

Alternative

method CH3COOH + PCl5 ——> CH3COCl + POCl3 + HCl

phosphorus(V) chloride

slide29

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

slide30

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, acyl chlorides and acid anhydrides

Reactivity Unreactive compared with acids and acyl chlorides

METHYL ETHANOATE

ETHYL METHANOATE

slide31

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, acyl chlorides and acid anhydrides

Reactivity Unreactive compared with acids and acyl chlorides

Isomerism Esters are structural isomers of carboxylic acids

METHYL ETHANOATE

ETHYL METHANOATE

slide32

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

react with alcohols hydrolysed to acids

slide33

PREPARATION OF ESTERS - 1

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’

slide34

PREPARATION OF ESTERS - 2

Reagent(s) alcohol + acyl chloride

Conditions reflux under dry conditons

Equatione.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.

slide35

PREPARATION OF ESTERS - 3

Reagent(s) alcohol + acid anhydride

Conditions reflux under dry conditons

Equatione.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.

slide36

HYDROLYSIS OF ESTERS

Hydrolysis is the opposite of esterification

ESTER + WATER CARBOXYLIC ACID + ALCOHOL

HCOOH + C2H5OH

METHANOIC ETHANOL

ACID

ETHYL METHANOATE

slide37

HYDROLYSIS OF ESTERS

Hydrolysis is the opposite of esterification

ESTER + WATER CARBOXYLIC ACID + ALCOHOL

HCOOH + C2H5OH

METHANOIC ETHANOL

ACID

ETHYL METHANOATE

METHYL ETHANOATE

slide38

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

slide39

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

slide40

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

slide41

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

slide42

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

slide43

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

slide44

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

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 compounds

• the quality of a soap depends on the oils from which it is made

slide45

FATTY ACIDS

Carboxylic acids that are obtained from natural oils and fats; they can be…

Saturated CH3(CH2)16COOH octadecanoic acid

(stearic acid)

slide46

FATTY ACIDS

Carboxylic acids that are obtained from natural oils and fats; they can be…

Saturated CH3(CH2)16COOH octadecanoic acid

(stearic acid)

9

Unsaturated CH3(CH2)7CH=CH(CH2)7COOH octadec-9-enoic acid

(oleic acid)

cis (Z) isomer

trans (E) isomer

slide47

FATTY ACIDS

Carboxylic acids that are obtained from natural oils and fats; they can be…

Saturated CH3(CH2)16COOH octadecanoic acid

(stearic acid)

9

Unsaturated CH3(CH2)7CH=CH(CH2)7COOH octadec-9-enoic acid

(oleic acid)

cis (Z) isomer

trans (E) isomer

12 9

CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH

octadec-9,12-dienoic acid (linoleic acid)

slide48

FATTY ACIDS AND HEALTH

Saturated • solids at room temperature

• found in meat and dairy products

• are bad for health

• increase cholesterol levels - can lead to heart problems

slide49

FATTY ACIDS AND HEALTH

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 • contain just one C=C

• thought to be neutral to our health

• found in olives, olive oil, groundnut oil, nuts, avocados

slide50

FATTY ACIDS AND HEALTH

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 • contain just one C=C

• thought to be neutral to our health

• found in olives, olive oil, groundnut oil, nuts, avocados

Poly

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

slide51

FATTY ACIDS AND HEALTH

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 • contain just one C=C

• thought to be neutral to our health

• found in olives, olive oil, groundnut oil, nuts, avocados

Poly

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

slide52

OMEGA 3 and 6 FATTY ACIDS

Omega 3 - fatty acids lower the total amount of fat in the blood

and can lower blood pressure and decrease

the risk of cardiovascular disease

3

W (omega) end CH3CH2CH=CHCH2CH2CH2CH2CH=CH(CH2)7COOH

The omega numbering system starts from the opposite end to the carboxylic acid group

slide53

OMEGA 3 and 6 FATTY ACIDS

Omega 3 - fatty acids lower the total amount of fat in the blood

and can lower blood pressure and decrease

the risk of cardiovascular disease

3

W (omega) end CH3CH2CH=CHCH2CH2CH2CH2CH=CH(CH2)7COOH

Omega 6 - fatty acids reduce the risk of cardiovascular disease but

can contribute to allergies and inflammation

6

W (omega) end CH3CH2CH2CH2CH2CH=CHCH2CH=CH(CH2)7COOH

slide54

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

slide55

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

slide56

BIOFUELS

What are they?

Liquid fuels made from plant material and recycled elements of the food chain

Biodiesel

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 (CO2) burden and produces drastically reduced engine emissions. It is non-toxic and biodegradable.

vegetable oil

glycerol

biodiesel

slide57

BIOFUELS

Advantages • renewable - derived from sugar beet, rape seed

• dramatically reduces emissions

• carbon neutral

• biodegradable

• non-toxic

• fuel & exhaust emissions are less unpleasant

• can be used directly in unmodified diesel engine

• high flashpoint - safer to store & transport

• simple to make

• used neat or blended in any ratio with petroleum diesel

slide58

BIOFUELS

Advantages • renewable - derived from sugar beet, rape seed

• dramatically reduces emissions

• carbon neutral

• biodegradable

• non-toxic

• fuel & exhaust emissions are less unpleasant

• can be used directly in unmodified diesel engine

• high flashpoint - safer to store & transport

• simple to make

• used neat or blended in any ratio with petroleum diesel

Disadvantages • poor availability - very few outlets & manufacturers

• more expensive to produce

• poorly made biodiesel can cause engine problems

slide59

BIOFUELS

Advantages • renewable - derived from sugar beet, rape seed

• dramatically reduces emissions

• carbon neutral

• biodegradable

• non-toxic

• fuel & exhaust emissions are less unpleasant

• can be used directly in unmodified diesel engine

• high flashpoint - safer to store & transport

• simple to make

• used neat or blended in any ratio with petroleum diesel

Disadvantages • poor availability - very few outlets & manufacturers

• more expensive to produce

• poorly made biodiesel can cause engine problems

Future

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

slide60

AN INTRODUCTION TO

CARBOXYLIC ACIDS AND THEIR DERIVATIVES

THE END

© 2009 JONATHAN HOPTON & KNOCKHARDY PUBLISHING