N5 Homologous Series Revision of homologous series including alkanes, alkenes, cycloalkanes, amines Reactions of alkenes including halogenoalkanes Systematic.

N5 Homologous Series Revision of homologous series including alkanes, alkenes, cycloalkanes, amines Reactions of alkenes including halogenoalkanes Systematic naming of hydrocarbons, including branched hydrocarbons.

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

Homologous series Homologous series General formula Functional group
Examples of homologous groups include: Homologous series General formula Functional group Alkanes CnH2n + 2 Alkenes CnH2n C=C Alkynes CnH2n - 2 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 Meth Eth Prop But Pent
Hex Hept Oct 1 2 3 4 5 6 7 8 General formula CnH2n+2

Shortened structural formula
Alkanes CH3CH2CH3 Full Structural formula Shortened structural formula C3H8 Molecular formula

N5 Alkanes

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. CH3CH ½ O2  2 CO H2O H = kJ mol -1

Structural Isomers Isomers are compounds with the same molecular formula but different structural formulae. H C CH3 butane methylpropane Here, you can see that 2-methylpropane has a side chain.

Isomers or not isomers? 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: 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
Alkanes Identify the longest chain Identify the ‘branches’ and name them. Number the carbon atoms on the longest chain, at the end giving the lowest numbers for the branches. 4. Write the branches in alphabetical order. 5. If there are more branches with the same name use di, tri etc

Naming Organic Compounds, Alkanes
Worked examples

H C CH3 2-methylbutane

H CH3 C 2,2-dimethylbutane

7-ethyl-3-methyldecane
CH2 CH3 7-ethyl-3-methyldecane

Draw full structural formula for 2,3,3-trimethylpentane
CH3 CH3 CH3

C2H5 CH3 CH3CHCHCHCH2CH3 3-ethyl-2,4-dimethylhexane

Problems for you to try:
1. Draw the shortened structural formulae of a) 2,4-dimethylhexane b) 4-ethyl-3-methyloctane c) 2,2,4,4-tetramethylpentane 2. Work out the systematic names of the following compounds. a) b) c)

N5 Cycloalkanes

Cycloalkanes: have a ring structure and are saturated (contain only single bonds). Name Cyclopropane Cyclobutane Cyclopentane Cyclohexane Cycloalkane Molecular Formula C3H6 C4H8 C5H10 C6H12 CnH2n Structural Formula (CH2)n

Branched Cycloalkanes
methylcyclopentane 1,2-dimethylcyclohexane 1,4-dimethylcyclohexane

N5 Alkenes

Alkenes Name No C’s Eth Prop But Pent Hex Hept Oct 2 3 4 5 6 7 8
Alkenes are hydrocarbons with the general formula CnH2n Name No C’s Eth Prop But Pent Hex Hept Oct 2 3 4 5 6 7 8

Shortened structural formula
Alkenes H C C = CH3CHCH2 Full Structural formula Shortened structural formula C3H6 Molecular formula

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

Structural Isomers Ethene 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
Alkenes Identify the longest chain, that contains a double bond. Identify the ‘branches’ and name them. Number the carbon atoms on the longest chain, starting from the end nearest the double bond. 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

Naming Organic Compounds, Alkenes
Worked examples

Naming Organic Compounds, Alkenes
H H C = H H C C C H H H H but-1-ene

Draw full structural formula for but-2-ene
H C = H H C C C H H H H H

H H C = H H H C C C C H H CH3 H H H 4-methylpent-2-ene

H C2H5 C CH3 = C2H5 H H C C C C = C CH3 H CH3 H H H 5,5-dimethylhept-2-ene

Draw the shortened structural formulae of a) oct-4-ene b) 3-ethylpent-1-ene c) 4,4-dimethylhex-2-ene 2. Work out the systematic names of the following compounds.

Reactions of Alkenes Addition reactions involving:
Hydrogen (Hydrogenation) Halogens Hydrogen Halides Water (Hydration)

Addition Reactions of Alkenes
Hydrogenation, the reaction of an alkene with hydrogen is an example of an addition reaction. H-H + Propene Propane

Addition Reactions of Alkenes
Halogenation, the reaction with halogens is another example of an addition reaction + Br-Br orange/red colourless colourless 1,2-dibromopropane propene This can be used for a test for unsaturation

halide attaches to the C
Reaction of Alkenes Reaction with Hydrogen Halides H-I + 2 -iodopropane Normally the H from the halide attaches to the C which already has the most hydrogen’s. or 1 -iodopropane

Draw the full structural formulae for the hydration of ethene above.
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. Conc Phosphoric acid CH2 = CH H2O CH3CH2 OH

Addition reactions

Naming Halogenoalkanes
Worked examples 41

H Br C 1,2-dibromoethane 42

H Br C 1,1-dibromoethane 43

3-chloro-2,2-dimethylpentane
Cl 3-chloro-2,2-dimethylpentane 44

Halogen Derivatives (Haloalkanes)
Halogenalkanes and halogenalkenes CHCl3 Chloroform Freon Correcting fluid Gortex, Teflon Solvent for grease Vinyl chloride Paint Stripper Degreasing agent Anesthetic CCl2=CCl2 CCl2F2 CCl4 CH3CCl3 CCl2H2 CF2=CF2 CH2=CHCl 45

Chlorofluorocarbons: CFC’s
All CFC’s are very unreactive, are not flammable and not toxic. They are used as flame retardants. CCl2F2 The first refrigerant, and in aerosols. CCl3F Used as a blowing agent to make expanded foam Recently hydrofluorocarbons have replaced some CFC’s. e.g. 1,1,1,2-tetrafluoroethane is used as a refrigerant. 46

Ozone destruction O3 ClO + O Cl + O2 CCl3F CCl2F + Cl Cl + O3 ClO + O2
CFC’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 ( ) . When UV light breaks bonds, free radicals are formed. Free radicals have unpaired electrons and, as a result, are highly reactive. ClO + O Cl + O2 CCl3F CCl2F + Cl U.V.light Cl + O3 ClO + O2 Free radicals react with O3, the reaction is complex, but one Cl free radical can catalyse the break down 1 million O3 molecules. We will look at free radicals in more detail later in the unit!!! 47

Amines 48

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 contain the Amino Functional Group. “R” Indicates any carbon groups. 49

Naming Amines CH3NH2 CH3CH2NH2
Amines with small chains can be named with the carbon chains as branches. CH3NH2 Methylamine CH3CH2NH2 Ethylamine Dimethylamine Trimethylamine Larger chains use the prefix ‘amino’ and the name of the alkane from which they are derived. Pentane 2-aminopentane 50

ethylamine trimethyl amine
Amines Amines with low molecular mass are volatile gases and liquids. They resemble ammonia in having strong “fishy” smells. ethylamine trimethyl amine putrescine cadaverine H2N(CH2)4NH H2N(CH2)5NH2 3,4-diaminobutane ,5-diaminopentane 51

Reactions of Amines Amines are bases. Like ammonia they react with acids to form salts. NH HCl → NH4+Cl- ammonia hydrochloric ammonium chloride acid CH3NH HCl → CH3NH3+Cl- methylamine hydrochloric methylammonium chloride 52

Aromatics

Aromatic Hydrocarbons
Benzene is the simplest member of the class of aromatic hydrocarbons. C6H6 Benzene was originally thought to have the following structure. Kekulé suggested it contained alternating double and single bonds. 54

Aromatic compounds Although 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 the bonds are the same length. 55

Aromatic compounds Although 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. 56

Aromatic compounds A 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 57

Aromatic compounds Aspirin 2-ethanoyloxybenzenecarboxcyclic acid
COOH COOCH3 Aspirin 2-ethanoyloxybenzenecarboxcyclic acid OH NHCOCH3 Paracetamol 4-hydroxyphenylethanamide 58

Alcohols 11/11/2018

Alcohols 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.

N5 Alcohols *Draw the full structural formula for: Methanol, CH3OH
Homologous Series containing the hydroxyl (-OH) functional group General formula: CnH2n+1OH *Draw the full structural formula for: Methanol, CH3OH Ethanol C2H5OH Propanol C3H7OH

Isomers * Draw the full structural formula of propanol*
Straight chain isomers of Alkanols: Propanol has 2 isomers, propan-1-ol and propan-2-ol. C H OH C H OH propan-1-ol propan-2-ol

Naming Alkanols H H H H H C C C C H H H H OH butan-1-ol

Naming Alkanols CH3(CH2)5CHOHCH3 octan-2-ol

Naming Alkanols CH3CH2CH2CH(C2H5)CHOHCH3 3-ethylhexan-2-ol

Naming Alkanols H H H H H C C C C H H CH3 H OH 3-methylbutan-1-ol

*Draw the full structural formula for glycerol*
Other Alcohols Cycloalcohols Cyclohexanol Diols (dihydric) C OH H 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*

Ethanol C2H5OH Functional group -OH
Hydroxyl group H O R - + Functional group -OH Hydrogen 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. Ethanol is a good solvent, it behaves both like water and other hydrocarbon solvents.

Uses of Alcohols

Uses of Ethanol Solvents: 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.

Uses of ethanol Fuel: Increasingly seen as an important fuel.
CH3CH2OH O2  2 CO H2O H = kJ mol -1 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 methanol Methanol 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

Classification of Alkanols
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) R2 R C O H R3 R1, R2 and R3 can represent Hydrogens or any sized length of carbon chain, like a branch .They are referred to as alkyl groups

Classification of Alkanols
primary secondary tertiary *Give the systematic name for each of the alcohols above*

Classify the following as primary, secondary or tertiary alcohols: CH3CH2CH2OH

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 an alkanoic 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 alkanoic acids 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.

propanoic acid Naming Organic Compounds, Alkanoic acids H H H C C C
O - H H H O propanoic acid

Naming Organic Compounds, Alkanoic acids
CH3 H H H C C C C O - H H CH3 H O 3-methylpentanoic acid

H CH3 H H C C C C O - H H CH3 H O 3,3-dimethylbutanoic acid

CH3(CH2)5COOH heptanoic acid

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  (CH3COO)2Mg + H2 CH3COOH + NaOH  CH3COONa + H2O Magnesium ethanoate Sodium ethanoate CH3COOH + K2CO  2 CH3COOK + H2O + CO2 Potassium ethanoate

Uses of Carboxylic Acids

Uses for Carboxylic acids
Carboxylic 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 preservation Vinegar has been used for millennia to preserve foods. There are many other foods where a proportion of ethanoic acid is added not only to enhance flavour, but also to help prevent food spoilage.

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

N5 Homologous Series Revision of homologous series including alkanes, alkenes, cycloalkanes, amines Reactions of alkenes including halogenoalkanes Systematic.

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N5 Homologous Series Revision of homologous series including alkanes, alkenes, cycloalkanes, amines Reactions of alkenes including halogenoalkanes Systematic.

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