Topic 6 organic chemistry part 1

General formula - algebraic formula that can be applied to chemicals in the family Molecular formula - The actual number of atoms in a molecule or element so ethane is C2H6 Empirical formula - Simplest whole number ratio of atoms in a compound Structural formula - the arrangement of atoms in a molecule without showing bonds CH3CH3CH3… Skeletal formula - shows bonds of the carbon skeleton only Displayed formula - shows all the bonds in a molecule

Group of compounds that have the same functional group and general formula Successive members increase by CH2 every time

• Find the length of the stem by counting th largest continuous chain • The functional group on the molecule normally tells you the ending of the name (suffix) • Number the carbon chain so that the functional group sits on the lowest possible number carbon • Make a note of the carbon number the functional group is attached to, place this number before the suffix. • Any side chains and less important functional groups are written as prefixes in alphabetical order • If there is more than 1 identical functional group or side chain, but di or tri or tetra

Polymerization - joining smaller monomers together to form a very long chain Addition - joining molecules together to form a larger one Hydrolysis - splitting a molecule into 2 using OH- or H+ from a H2O molecule Substitution - Replacing one atom with another molecule Elimination - Some atoms break away from a larger molecule Reduction - when a species gains electrons in a reaction Oxidation - when a species loses electrons in a reaction

Shows the movement of electrons during a chemical reaction Use curly arrows to show the movement of a pair of electrons Always starts from an electron-dense area and ends where you are moving the electrons to or the formation of a new bond.

Free radical substitution - used when halogens react with alkanes to form halogenoalkanes Electrophilic addition - used in adding halogens and hydrogen halides to alkenes to make halageno alkanes Nucleophilic substitution - Used in primary halogenoalkanes and aqueous KOH to make alcohols. Amines are made by reacting with ammonia

Structural isomers have the same molecular formula but different structural formula Chain isomers - Same molecular formula but different arrangement of the carbon skeleton Positional isomer - Same molecular formula but different position of the fiunctional group on the carbon skeleton Functional group isomer - Same molecular formula but different functional group

Saturated hydrocarbons - CnH2n+2 Saturated which means carbon is bonded 4 times with the maximum number of hydrogens possible Cycloalkanes are slightly different they have a general formula of CnH2n with 2 hydrogens per carbon

It is the breaking of a covalent bond and the electron pair can be distributed in 2 ways Heterolytic fission is when electrons are distributed unequally to 2 different ions. The double-headed arrow shows the movement of a pair of electrons Homolytic fission is when electrons in the bond are being shared equally to form 2 charged radicals

• Initiation - Sunlight breaks the cl–cl bond in a process called photodissociation. The bond breaks equally producing 2 highly reactive radicals Cl – Cl —–> Cl. + Cl. • Propagation - The Cl radical reacts with a methane molecule to make a methyl radical The methyl radical reacts with a Cl2 molecule forming chloromethane and a Cl. radical This Cl. radical can react with more methane Cl. + Ch4 —-> Hcl + CH3. Ch3. + cl2 —-> Ch3Cl + Cl. Termination - 2 radicals react to make a stable non radical molecule Ch3. + Cl. —–> Ch3Cl

Producing just chloromethane is difficult as further reactions occur producing a mixture of products If there is a lot of chlorine in the reaction mixture, we get di tri and tetra haloalkane Cl. + Ch3Cl —-> .Ch2Cl + Hcl .Ch2Cl + Cl2 —-> .Ch2Cl2 + Cl. Dichloromethane is formed. This can also react further and make trichloromethane. Tri can react further to make tetra. Have to be separated depending on what we want. You can add excess methane to reduce the amount of multiple substitution

Crude oil is vaporised using a furnace to about 350 degrees The vaporised oil enters the column and ruses through the trays. The longest hydrocarbons don’t vaporise and stay at the bottom The column has a temp gradient, it is cooler at the top. As the vapour rises parts of the mixture condenses at different temperatures as there are different chain lengths and hence different BP’s Heavier fractions can be cracked to higher demand for lighter fractions

Heavier fractions can be cracked to higher demand for lighter fractions Thermal cracking: 100 degrees and 70atm Alkenes are used to make polymers such as plastic Products of thermal cracking are mainly alkenes Catalytic cracking: 450 degrees and slight pressure Zeolite catalyst used to lower temp Products are mainly aromatic hydrocarbons useful in fuels for vehicles

They can be reformed into cycloalkanes and aromatic molecules The problem is that straight-chain alkanes create knocking in a car engine. Knocking is when straight-chain alkanes explode upon compression. Adding branched and cyclic alkanes reduces knocking and increases engine efficiency Cyclic and branched alkanes can be made using straight-chain alkanes and a platinum catalyst in a process called reforming Hexane is reformed to cyclohexane and then benzene

They burn in oxygen completely to form CO2 and H2O. They’re very good fuels as most burn readily to produce large amounts of energy The larger the alkane the more energy they produce

When alkanes burn with limited oxygen they produce CO and C. Carbon monoxide is poisonous as it bonds with haemoglobin in the blood and prevents oxygen bonding. Carbon monoxide can be removed using a catalytic converter. Soot can cause breathing problems, make buildings dirty and clog up engines

Burning fossil fuels can release SO2 and oxides of nitrogen which contribute to acid rain. It can cause damage to plants, kill fish, and cause erosion of buildings. SO2 is acidic which can react with water in the atmosphere to form sulfuric acid which falls as acid rain Oxides of nitrogen are formed when nitrogen and oxygen from the air are heated in the engine and react

Found mainly in vehicles and help to reduce harmful pollutants entering the atmosphere Help reduce the amount of unburnt hydrocarbons and oxides of nitrogen from going into the atmosphere They convert harmful gases into less harmful products like water vapor, nitrogen and oxygen

Advantages: Renewable Produce CO2 when burnt but are classed as carbon neutral as the CO2 is absorbed by the plants when it’s growing Disadvantages: Expensive to convert existing petrol engines to take fuels with a higher concentration of ethanol Land that can be used to grow food is being used for oil - food shortages

The double bond contains a sigma bond and a pi bond In a sigma bond, that is when 2s orbitals overlap. Strong electrostatic attraction between the nuclei and shared pair of electrons due to the high electron density between nuclei. This makes the sigma bond have a high bond enthalpy In a pi bond, it is the parallel overlap of 2p orbitals. They are dumbbell-shaped, and when they merge they form 2 oblong shapes. One on the top and one on the bottom. Pi bonds are weaker as the electron density is spread out above and below the nuclei. The electrostatic attraction is weaker so Pi bonds have a lower bond enthalpy

The double bonds in alkenes have a high electron density, It’s the high electron density area that makes them reactive. 4 electrons are being shared in the double bond. Alkanes only have sigma bonds which makes them non-polar and so not very reactive compared to alkenes. Pi bonds stick out a little and the whole double bond has a high electron density which means they are open to attack from electrophiles. They also have low bond enthalpy which is another reason why alkenes are reactive

Unsaturated with CnH2n which means a least 1 double covalent bond Double bonds have a very high electron density which makes them reactive Cycloalkenes have 2 fewer hydrogens than their straight-chain version of the same molecule

Same structural formula but a different arrangement of atoms in space Atoms can’t rotate around the C=C bond and is rigid. E/Z isomerism happens when you have 2 different groups of atoms on the same carbon E = opposite side Z = same side

We use this when we have 4 different groups around the double bond 1) Label carbons with the double bond as 1 and 2 2) Calculate the atomic number of the first element directly bonded to the c=c bond. The atom with the highest atomic number is given a higher priority