SJA Alcohols and Carboxylic acids...Homologous series Examples of homologous groups include: Homologous series General formula Functional group Alkanes CnH2n + 2 Alkenes CnH2n C=C

Learning Outcomes :

Homologous Series

• Revision of homologous series including alkanes, alkenes, cycloalkanes, amines

• Reactions of alkenes including halogenoalkanes• Systematic naming of hydrocarbons, including branched

hydrocarbons.

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Compounds in the same homologous series:-• have a similar structure (functional group)• fit a general formula• have similar properties• undergo the same reactions

Homologous seriesExamples of homologous groups include:

Homologous series

General formula

Functional group

Alkanes CnH2n + 2

Alkenes CnH2n C=C

Alkynes CnH2n - 2 C=C

Alkanols CnH2n + 1 OH R – OH

Alkanoic acids CnH2n + 1 COOH R – COOH

Alkanals CnH2n + 1 CHO R – CHO

Alkanes

General formula CnH2n+2

Name No. C’s

MethEthPropButPentHexHeptOct

12345678

Alkanes

Full Structural formula

CH3CH2CH3

Shortened structuralformula

Molecular formula

C3H8

C C C

H

H

H

H

H

H

H

H

Alkanes

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Alkanes• Alkanes contain only single carbon to carbon

bonds they are described as saturated hydrocarbons.

• Alkanes are not very reactive (they do not react with acids, alkalis or bromine water).

• They do burn making them important fuels.

CH3CH3 + 3½ O2 è 2 CO2 + 3 H2O

∆H = - 1560 kJ mol -1

Structural IsomersIsomers are compounds with the same molecular formula but different structural formulae.

H

H

C

H

H

H

H

C

H

HC

H

H

C H

H

C

H

H

C

CH3

H

H

H

C

butane 2-methylpropane

Here, you can see that 2-methylpropane has a side chain.

Take care, the same molecule can be represented in different ways by:•Drawing the branch below instead of above the carbon chain.•Drawing the branch at the other end of the chain.•By drawing a bend in the longest chain.

Isomers or not isomers?

Isomers: Boiling points

Use your understanding of structure and bonding to explain why the boiling point is increasing?

Isomers: Boiling points

As the amount of branching increases, the tendency is for the boiling point to decrease.

The structure is more compact, smaller surface area, weaker London's dispersion forces.

Naming Compounds of Carbon

1. Identify the longest chain2. Identify the ‘branches’ and name them.3. Number the carbon atoms on the longest

chain, at the end giving the lowest numbersfor the branches.

4. Write the branches in alphabetical order.5. If there are more branches with the same

name use di, tri etc

Alkanes

Worked examples

Naming Organic Compounds, Alkanes

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H

H

C

CH3

H

C

H

H

C

H

HH

H

C

H

2-methylbutane

H

CH3

C

CH3

H

C

H

H

C

H

HH

H

C

H

2,2-dimethylbutane

H

H

C

CH2

H

C

H

H

C

H

H

C

H

H

C

CH2

CH3

C

H

H

CH3 CH2

CH3

H

H

C

H

CH3

C

H

H

7-ethyl-3-methyldecane

H

H

C

H

C

H

C

H

C

HCH3

H

H

C

H

H

CH3

CH3

Draw full structural formula for 2,3,3-trimethylpentane

C2H5

CH3CH3

CH3CHCHCHCH2CH3

3-ethyl-2,4-dimethylhexane

Problems for you to try:

1. Draw the shortened structural formulae ofa) 2,4-dimethylhexaneb) 4-ethyl-3-methyloctanec) 2,2,4,4-tetramethylpentane

2. Work out the systematic names of the following compounds.

a) b) c)

Cycloalkanes

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Cycloalkanes:

Name Cyclopropane Cyclobutane Cyclopentane Cyclohexane Cycloalkane

MolecularFormula C3H6 C4H8 C5H10 C6H12 CnH2n

StructuralFormula

(CH2)n

have a ring structure and are saturated (contain only single bonds).

Branched Cycloalkanes

methylcyclopentane

1,4-dimethylcyclohexane 1,2-dimethylcyclohexane

Alkenes

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AlkenesAlkenes are hydrocarbons with the general formula CnH2n Name No C’s

EthPropButPentHexHeptOct

2345678

Alkenes

Full Structural formula

CH3CHCH2

Shortened structuralformula

Molecular formula

C3H6

H

C

H

H CHH

C =H

Alkenes

Alkenes contain a carbon to carbon double bond they are described as unsaturated hydrocarbons.

Structural IsomersEthene has no isomers. Propene is isomeric with cyclopropene

Isomers of alkenes can arise for two reasons

• the position of the double bond in the chain can vary

• the chain can be straight or branched

Naming Compounds of Carbon

1. Identify the longest chain, that contains a double bond.

2. Identify the ‘branches’ and name them.3. Number the carbon atoms on the longest chain,

starting from the end nearest the double bond. 4. Pick the lowest number and give the position of the

double bond.4. Write the branches in alphabetical order.5. If there are more branches with the same name use

di, tri etc

Alkenes

Worked examples

Naming Organic Compounds, Alkenes

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but-1-ene

H

H

C

H

H

C

H

H

C

HH

C CC =

Naming Organic Compounds, Alkenes

Draw full structural formula for but-2-ene

H

H

C

H

HC

H

H

C

HH

C=

4-methylpent-2-ene

H

H

C

H

H

C

H

H

C

HCH3

C

H

C CC C= H

H

5,5-dimethylhept-2-ene

H

H

C

H

C2H5

C

H

H

C

H

CH3

CH3

C C

H

=

C2H5

C C CH3C C=

Problems for you to try:

1. Draw the shortened structural formulae ofa) oct-4-eneb) 3-ethylpent-1-enec) 4,4-dimethylhex-2-ene

2. Work out the systematicnames of the followingcompounds.

Reactions of AlkenesAddition reactions involving:

• Hydrogen (Hydrogenation)• Halogens• Hydrogen Halides• Water (Hydration)

Addition Reactions of AlkenesHydrogenation, the reaction of an alkene with hydrogen is an example of an addition reaction.

+ H-H

Propene Propane

C C C

H

H

H

H H

HH

HC C C

H

H

H

H H

H

Addition Reactions of AlkenesHalogenation, the reaction with halogens is another example of an addition reaction

1,2-dibromopropane

colourless

+ Br-Brorange/red

This can be used for a test for unsaturation

C C C

H

H

H

H H

Hcolourless

C C C

H

H

H

Br Br

HH

H

propene

Reaction with Hydrogen Halides

+ H-I

2 -iodopropane

1 -iodopropane

orNormally the H from thehalide attaches to the C

which already has themost hydrogen’s.

Reaction of Alkenes

C C C

H

H

H

H H

H

C C C

H

H

H HH

H

H I

C C C

H

H

H HH

H

HI

Alkenes with water• Concentrated sulphuric acid reacts with ethene• The reaction is an example of Hydration.• The overall effect of the acid is to combine water with

ethene. • At one time, this was the most important method for

manufacturing ethanol from ethene. Nowadays, direct catalytic hydration of ethene is used.

Draw the full structural formulae for the hydration of ethene above.

CH2 = CH2 + H2O CH3CH2 OHConc Phosphoric acid

Addition reactions

Naming Halogenoalkanes

Worked examples

H

Br

C

H

Br

C H

H

1,2-dibromoethane

H

Br

C

H

BrC HH

1,1-dibromoethane

H

H

C

H

CH3

C

H

Cl

H

C

H

H

CH3

C

H

C

H

3-chloro-2,2-dimethylpentane

Halogen Derivatives (Haloalkanes)Halogenalkanes and halogenalkenes

CHCl3CCl4

CH3CCl3

CCl2=CCl2

CH2=CHClCF2=CF2

CCl2F2

CCl2H2

ChloroformFreon

Correcting fluid

Gortex, Teflon

Solvent for grease

Vinyl chloride

Paint Stripper

Degreasing agent

Anesthetic

Chlorofluorocarbons: CFC’sAll CFC’s are very unreactive, are not flammable and not toxic. They are used as flame retardants.

CCl3F

CCl2F2

e.g. 1,1,1,2-tetrafluoroethane is used as a refrigerant.

Used as a blowing agent to make expanded foam

Recently hydrofluorocarbons have replaced some CFC’s.

The first refrigerant, and in aerosols.

Ozone destruction O3CFC’s are very stable, lasting for 100 years in the atmosphere. So over time, CFC’s can reach the stratosphere. Here, UV radiation attacks the CFC’s forming free radicals ( ) .

Free radicals react with O3, the reaction is complex, but one Cl free radical can catalyse the break down 1 million O3molecules. We will look at free radicals in more detail later in the unit!!!

ClO + O Cl + O2

CCl3F CCl2F + ClU.V.light

Cl + O3 ClO + O2

When UV light breaks bonds, free radicals are formed. Free radicals have unpaired electrons and, as a result, are highly reactive.

Amines

The structure of Amines is closely related to ammonia.

Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a carbon containing group

Amines

Amines contain the Amino Functional Group.

“R” Indicates any carbon groups.

Naming AminesAmines with small chains can be named with the carbon chains as

branches.

Larger chains use the prefix ‘amino’ and the name of the alkanefrom which they are derived.

CH3NH2Methylamine

CH3CH2NH2Ethylamine

CH3N

H

CH3 CH3N

CH3

CH3

TrimethylamineDimethylamine

CH3 CH CH2 CH2CH3

NH2

CH3 CH2 CH2 CH2 CH3Pentane 2-aminopentane

AminesAmines with low molecular mass are volatile gases and liquids. They resemble ammonia in having strong “fishy” smells.

ethylamine trimethyl amine

putrescine cadaverineH2N(CH2)4NH2 H2N(CH2)5NH2

3,4-diaminobutane 1,5-diaminopentane

Reactions of AminesAmines are bases. Like ammonia they react with acids to form salts.

NH3 + HCl → NH4+Cl-

ammonia hydrochloric ammonium chlorideacid

CH3NH2 + HCl → CH3NH3+Cl-

methylamine hydrochloric methylammonium chlorideacid

Aromatics

Aromatic Hydrocarbons

Benzene was originally thought to have the following structure. Kekulé suggested it contained alternating double and single bonds.

Benzene is the simplest member of the class ofaromatic hydrocarbons. C6H6

Aromatic compoundsAlthough this structure was a good attempt in its time, there are serious problems with it:

Benzene does not decolurise bromine water and does not undergo addition reactions.

X ray analysis confirms all thebonds are the same length.

Aromatic compoundsAlthough you will still come across the Kekulé structure for benzene, for most purposes we use the following structure.

The hexagon shows the ring of six carbon atoms, each of which has one hydrogen attached. The circle represents a cloud of six delocalised electrons.

Aromatic compoundsA benzene ring that has had a hydrogen removed is called a phenyl group

Aromatic compounds are important feedstocks and are used in dyes, herbicides, insecticides fungicides, medicines and plastics

Aromatic compounds

COOHCOOCH3

Aspirin2-ethanoyloxybenzenecarboxcyclic acid OH

NHCOCH3

Paracetamol4-hydroxyphenylethanamide

CfE Higher Chemistry Unit 2: Natures Chemistry

Alcohols

24/01/2018

Learning Outcomes :• Give systematic names, structural formulae and isomers for

branch chained alcohols.• The structure of diols, triols and the effect of hydrogen

bonding on properties of these molecules.• Classification of alcohols as primary, secondary and tertiary.

Alcohols

Alcohols• Homologous Series containing the hydroxyl (-OH) functional

group

• General formula: CnH2n+1OH

*Draw the full structural formula for:

Methanol, CH3OH

Ethanol C2H5OH

Propanol C3H7OH

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Isomers

Propanol has 2 isomers, propan-1-ol and propan-2-ol.Straight chain isomers of Alkanols:

propan-1-ol propan-2-ol

CC C

H

H

H

H

H

H

OH

H

CC C

H

H

H

H

OH

H

H

H

* Draw the full structural formula of propanol*

Practice Question

butan-1-ol

H

H

C

H

H

C

H

H

H

C

OH

H

H

C

Naming Alkanols

Practice Question

octan-2-ol

CH3(CH2)5CHOHCH3

Naming Alkanols

Practice Question

3-ethylhexan-2-ol

CH3CH2CH2CH(C2H5)CHOHCH3

Naming Alkanols

Practice Question

3-methylbutan-1-ol

H

H

CH

H

C

H

H

H

COH

HCH3

C

Naming Alkanols

Other AlcoholsCycloalcohols Cyclohexanol

Diols (dihydric) Ethan-1,2-diol(Anti freeze)

Triols (trihydric)e.g. propan-1,2,3-triol or glycerol is used in cosmetics, paints and nitroglycerine explosives.

*Draw the full structural formula for glycerol*

C

C

C

C

C

C

H

H

H OH

H

H

H

H HH

H

H

CC

OH

H

H H

H

OH

Ethanol C2H5OH

Functional group -OHHydrogen bonding allows ethanol to dissolve in water,( pH 7. b.p. 78 oC.)

This effect decreases in alcohols as the length of the hydrocarbon chain increases.

CC H

H

H

H OH

H

Hydroxyl group

Ethanol is a good solvent, it behaves both like water and other hydrocarbon solvents.

HHH

OR Oδ-δ+

δ+

δ-

δ+

Uses of Alcohols

Uses of EthanolSolvents: In varnishes (as it evaporates easily), dyes, perfumes and drugs

Cleaning products: Meths is ethanol with added methanol.

Drinks: Ethanol is a natural product of fermentation. Ethanol cannot be more than 15% of the fermentation mixture, as ethanol is a poison and will kill the yeast. In the UK 8 g of ethanol is 1 UNIT.

CH3CH2OH + 3 O2 è 2 CO 2 + 3 H2O ∆H = - 1367 kJ mol -1

Uses of ethanolFuel: Increasingly seen as an important fuel.

• Ethanol can be used as a fuel in cars.

• Produced by fermentation

• e.g. sugar cane. It has an

• octane rating of 111. In Brazil about 20% of their ‘petrol’ is ethanol

Uses of methanolMethanol again burns to form carbon dioxide and water.

Methanol can be used as petrol additive or as a fuel in its own right. Octane rating of 114, also ‘clean’ burning. Toxic and corrosive

Classification of Alcohols

In alcohols the Carbon attached to the –OH can be attached to 0, 1, 2 or 3 other Carbon atoms

• 0 or 1 makes it primary as the OH is on the end carbon

• 2 is secondary (the OH is in the middle of a chain)

• 3 is tertiary (in the middle of a chain, opposite a branch)

R1, R2 and R3 can represent Hydrogens or any sized length of carbon chain, like a branch .They are referred to as alkyl groups

R2

R1 C O H

R3

Classification of Alkanols

Classification of Alkanols

C C OH

H

H

H

H

H

C CC

OH

H

H

HH

H

H H C CC

OH

H

H

CH3H

H

H H

primary secondary tertiary

*Give the systematic name for each of the alcohols above*

Practice QuestionProblems for you to try:Classify the following as primary, secondary or tertiary alcohols:

A. CH3CH2CH2OH

B.

C.

D.OH

Learning Outcomes :

CARBOXYLIC ACIDS

• In this section you can learn about the characteristic chemical properties of the family of carboxylic acids, and find out how they are put to good use in everyday consumer products.

Carboxylic Acids

• Vinegar’s chemical name is ethanoic acid, sometimes called acetic acid.

• It is a member of a group of compounds called carboxylic acids, which contain the carboxyl functional group (-COOH).

• If it is a straight chain hydrocarbon containing the carboxyl functional group it is known as analkanoic or carboxylic acid.

Carboxylic (Alkanoic) Acids•They contain the CARBOXYL functional group –COOH

•They have the general formula

CnH2n+1COOH

•Because of the ability of lower molecular sized alkanoicacids to form hydrogen bonds, they are soluble in water.

• They have high b.p.’s for the same reason.

•They also have a sharp smell. Human sweat contains a mixture of these compounds.

Testing Carboxylic Acids

ACTIVITY: Testing carboxylic acids. Test a selection of carboxylic acids to for smell, pH and reactivity.

NOTES• Show what functional group a carboxylic acid contains and what

the members of the alkanoic acid homologous series look like by drawing the full structural formulae and chemical formulae for the first four members of the alkanoic acid homologous series.

• After completing the experiments make a note of your observations. In particular you should record any trends in smell, pH and reactivity as the length of the carbon chain increases.

Reactions of Carboxylic Acids• ACTIVITY: Neutralisation of carboxylic acids.

Neutralise ethanoic acid using sodium hydroxide, using pH paper to check it is no longer acidic. Evaporate off the water to leave the salt, sodium ethanoate.

• NOTES• Write a note on the formation of salts from

carboxylic acids.• Write a word equation and a chemical equation for

the formation of sodium ethanoate from the neutralisation of ethanoic acid and sodium hydroxide.

CH

H

C

H

HC O - H

H O

propanoic acid

Naming Organic Compounds, Alkanoic acids

CHCH3

CH

HC

H

HC O - H

CH3 O

3-methylpentanoic acid

Naming Organic Compounds, Alkanoic acids

CHCH3

CH

H

C

H

HC O - H

CH3 O

3,3-dimethylbutanoic acid

Naming Organic Compounds, Alkanoic acids

heptanoic acid

CH3(CH2)5COOH

Naming Organic Compounds, Alkanoic acids

Alkanoic Acids Properties: Acids have a pH below 7.

Alkanoic acids are weak acids, so can react with some metals and alkalis.

2 CH3COOH + Mg è (CH3COO)2Mg + H2

CH3COOH + NaOH è CH3COONa + H2O

Magnesium ethanoate

Sodium ethanoate

CH3COOH + K2CO3 è 2 CH3COOK + H2O + CO2Potassium ethanoate

Uses of Carboxylic Acids

Uses for Carboxylic acidsCarboxylic acids are used in:• some food items. Vinegar is dilute ethanoic acid. This is

used in preparations for pickles, salads, sauces, etc. • the manufacture of soaps. Sodium salts of fatty acids are

used in soap and detergent industries. • medicines. Ethanoic acid is used in making aspirin. • industrial solvents. • preparing perfumes and artificial essences used in food

manufacturing. • are produced in your sweat glands. Dogs can track

humans by detecting the characteristic blend of these acids in your sweat.

Food preservationVinegar has been used for millennia to preserve foods.

There are many other foods where a proportion of ethanoicacid is added not only to enhance flavour, but also to help prevent food spoilage.

Removing lime-scale• The ability of carboxylic acids to react with carbonates

to form salts is exploited in some lime-scale removers.

• Lime-scale forms when hard water (water containing soluble calcium and magnesium salts) is boiled or allowed to evaporate. Under these conditions the soluble salts are changed into insoluble ones.

• For example, a water supply containing calcium hydrogen carbonate will deposit calcium carbonate when boiled.

Ca(HCO3)2(aq) → CaCO3(s) + H2O(l) + CO2(g)