A Level Chemistry - Organic Chemistry 1

Front 1

Formulae

Back 1

General formula - algebraic formula that describes any member of a family of compounds

Empirical formula - simplest whole number ratio of the atoms of each element in a compound

Molecular formula - number of atoms of each element in a compound

Structural formula - arrangement of the atoms

Skeletal formula - shows the bonds of the carbon skeleton only with functional groups

Displayed formula - shows arrangement of all the atoms and the bonds

Front 2

Homologous series

Back 2

Group of organic compounds with the same functional group and general formula

Front 3

Functional group

Back 3

Group of atoms in a molecule responsible for the characteristic reactions of that compound

Front 4

Reaction types

Back 4

Addition

Substitution

Elimination

Hydrolysis

Polymerisation

Oxidation

Reduction

Front 5

Structural isomers

Back 5

Same molecular formula, different structural formula

Chain isomers - different arrangements of the carbon skeleton, so have similar chemical properties but different physical properties

Positional isomers - functional groups arranged differently, so have different chemical properties and physical properties

Functional isomers - functional groups are different, so have different chemical properties and physical properties

Front 6

Alkanes

Back 6

General formula - C(n)H(2n+2)

Contain only carbon and hydrogen = hydrocarbon

All carbon-carbon bonds are single bonds = saturated

Front 7

Bond fission

Back 7

Bond fission is breaking a covalent bond.

Heterolytic fission - bond breaks unevenly and one of the atoms receives both electrons from the bonded pair, forming a cation and an anion.

Homolytic fission - bond breaks evenly and each atom receives one electron from the bonded pair, forming 2 electrically uncharged radicals

Hint 7

Radicals are species that have an unpaired electron, and are very reactive

Front 8

Radical substitution

Back 8

When halogens react with alkanes to form halogenoalkanes, a hydrogen atom is substituted for a halogen atom.

The reaction is initiated by UV light.

However, there may be further substitution reactions and the formation of a mixture of products

Hint 8

Reducing the chances of these by products forming by having excess methane, so there's greater chance of a Cl• reacting with CH4 molecule rather than CH3Cl molecule

Front 9

Initiation reactions

Back 9

Initiation reactions produce radicals.

Light provides enough energy to break the bond in halogen molecules - photodissociation - causing homolytic fission to occur, producing 2 radicals

Hint 9

Cl2 = 2Cl•

Front 10

Propagation reaction

Back 10

In propagation reactions, radicals are used up and created.

Hint 10

Cl• + CH4 = HCl + •CH3

•CH3 + Cl2 = CH3Cl + Cl•

Front 11

Termination reaction

Back 11

Radicals react together to form stable molecules

Hint 11

Cl• + •CH3 = CH3Cl

•CH3 + •CH3 = C2H6

Front 12

Crude oil

Back 12

Crude oil is a mixture of hydrocarbons - mostly alkanes.

It can be separated out by fractional distillation

Front 13

Fractional distillation

Back 13

● crude oil vaporized at 350°C

● crude oil vapours enter fractionating column and rise up through trays

● fractionating column gets cooler at the top

● different alkanes have different chain lengths and boiling points, so as crude oil vapours rise up column, different fractions condense at different temperatures and are removed at different levels of the column

● largest hydrocarbons with highest b.p. don't vaporize and found at bottom as residue

● smallest hydrocarbons with lowest b.p. don't condense and are removed from top as gases

Front 14

Cracking

Back 14

Longer chain alkanes are broken down into smaller chain hydrocarbons

Front 15

Thermal cracking

Back 15

Uses very high temperatures (1000°C) and pressure (70 atm) to crack long chain alkanes into lots of alkenes, which are used to make polymers

Front 16

Catalytic cracking

Back 16

Uses zeolite catalyst (hydrated aluminosilicate) at slight pressure and high temperature (450°C) crack long chain alkanes into mostly aromatic hydrocarbons and motor fuels.

Hint 16

Catalyst reduces costs by lowering temperature and pressure needed and speeding up the reaction

Front 17

Reforming

Back 17

Reforming is the processing of straight-chain hydrocarbons into branched-chain alkanes and cyclic hydrocarbons for efficient combustion.

Front 18

Combustion of alkanes

Back 18

Complete combustion - alkane + O2 = CO2 + H2O

Incomplete combustion - produces CO, C and H2O

Combustion only occurs between gases so liquid alkanes must be vaporized.

Combustion is an exothermic reaction.

Alkanes release a lot of energy when they burn, so are used as fuels.

Larger alkanes release more energy.

Front 19

Pollutants

Back 19

Pollutants, including carbon monoxide, oxides of nitrogen and sulfur, carbon particulates and unburned hydrocarbons, are formed during the combustion of alkane fuels.

Front 20

Carbon monoxide

Back 20

Carbon monoxide binds to haemoglobin in red blood cells, preventing the cells from carrying oxygen around the body, resulting in oxygen deprivation.

Front 21

Oxides of nitrogen and sulphur

Back 21

● Sulphur impurities in fossil fuels are burnt to produce sulphur dioxide gas.

● The high pressure and temperatures in car engines causes nitrogen and oxygen in the air to react, producing nitrous oxides.

When both gases enter the atmosphere, they're dissolved in moisture and converted into nitric acid and sulphuric acid. These fall as acid rain, destroying trees, corroding buildings and killing marine ecosystems.

Front 22

Catalytic converters

Back 22

Catalytic converters use platinum catalyst to remove pollutants from car exhausts by converting them into harmless gases, like water vapour and nitrogen, or even CO2

Front 23

Alternatives

Back 23

Fossil fuels are non renewable and are becoming more scarce.

Biofuels are fuels made from living matter

■ bioethanol - ethanol made by fermentation of sugars from crops like maize

■ biodiesel - refining renewable fats and oils like veg oil

■ biogas - breakdown of organic waste matter

They produce CO2 when burnt, but this is offset by the plants absorbing CO2 while growing, so are classed as carbon neutral, but only if grown at same rate as they're burnt.

Biodiesel and biogas can be made from waste that would've gone to landfill.

Reliable as they can be grown quickly and all year round.

Hint 23

Petrol car engines would need to be modified to use biofuels.

Land used to grow biofuels can't be used to grow food, aswell as water.

Deforestation for land to grow biofuels results in loss of habitats, and increased CO2 and CH4 emissions from burning and decaying wood.

CO2 produced while refining and transporting the fuels, and making fertilisers and powering agricultural machinery to grow and harvest crops.

High costs to refine biofuels.

Front 24

Sigma bond

Back 24

Single covalent bond formed by head on overlap of 2 atomic orbitals, with electron density concentrated between the 2 nuclei, along the axis of the bond

Free rotation is possible around the bond

Front 25

Pi bond

Back 25

Covalent bond formed by the sideways overlap of 2 p orbitals with electron density concentrated above and below the axis of the bond

Restricted rotation

Front 26

Nucleophile

Back 26

Electron rich and donates electrons

Front 27

Electrophile

Back 27

Electron poor and accepts electrons

Front 28

Rate of hydrolysis of halogenoalkanes

Back 28

■ Cl is most electronegative so C-Cl bond is shortest and has highest bond enthalpy, so reaction is slowest

■ I is least electronegative so C-I bond is longest and has lowest bond enthalpy, so reaction is fastest

■ 3° halogenoalkanes form the most stable carbocations so the halogen is more readily lost and the reaction is fastest

■ 1° halogenoalkanes form the least stable carbocations so the halogen is not readily lost and the reaction is slowest