organix

Hydrocarbons - made only of hydrogen and carbon

Aliphatic - carbons atoms form a straight or branched chains

Alicylic - carbon atoms form a ring

aromatic - carbon atoms form a ring and have delocalised electron system

Homologous series

Compounds with same functional group and similar chemical and physical properties. They differ by number of repeating units they contain. Same general formula

Functional group

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

Homolytic fission

When bond breaks, each electron in bond goes to a different atom

Forms

• highly reactive free radicals

• Each with an unpaired electron represented by a dot

Heterolytic fission

When bond breaks both electrons go in the same atom

• forms a (+) cation and (-)anion

When are bonds formed

• On the collision of two free radicals with unpaired electrons

• on the collision of opposite charged ions

Isomers

Molecules that have same molecular formula but a different arrangement of atoms

Structural isomers

Same molecular formula different structural formula

1) chain

2) positional

3) functional

• aldehydes and ketones

• Carboxylic and esters

• Alkenes and cycloalkanes

Stereoisomerism

Same structural and molecular formula but different arrangement of atoms in space

E/Z isomerism

Arises in alkenes due to restricted oration around C=C bond.

Carbon must have 2 different substituent attached

Cahn Ingold prelog rules

• substituent assigned priorities based on atomic mass

• 2 high priorities on same side - Z

• High priorities on different side - E

Alkanes

• saturated hydrocarbons

• CnH2n+2

• Non polar - similar electronegativities between hydrogen and carbon.

• Don’t react with polar reagents don’t attract nucleophiles and electrophiles

Factors affecting boiling points of Alkanes

1) chain length (molecular size) - increases B.P

• there’s a greater surface area and number of electrons for strong VDW forces

2) Branching - lowers B.P

• smaller surface area for contact between molecules

• Weaker VDW

Crude oil

mixtures of hydrocarbons

Fossil fuel formed from breakdown of plant and animal remains that have been subject to high pressure over millions of years.

Fraction

Group of hydrocarbons with similar boiling points

Fractional distillation

1. Crude oil is heated

2. Vapour enters fractionating column

3. Column has temperature gradient ( hot at bottom , cooler at top)

4. As chain length increases BP increases due to VDW forces needing more energy to overcome forces

5. Components condense at different heights depending on BP

6. Shorter chains condense at top, longer at bottom

Cracking

Converts longer chain hydrocarbons to more economically valuable shorter chain hydrocarbons

1) thermal cracking

• high temp ( 1000) and pressure (70)

• C-C breaks homolytically

• Forms atleast one alkane and lot of Alkanes

2) catalytic cracking

• low pressure and temp (450)

• zeolite catalyst ( silicon and aluminium oxide)

• Forms motor fuels ( branched and cycloalkanes) aromatic compounds

Fractions and their uses in order

1. Refinery gas - bottled gas

2. Gasoline - fuel for cars

3. Kerosene - aircraft fuel

4. diesel - fuel for cars, Lorries, buses

5. Fuel oil - ships , power stations

6. Bitumen - roads , roofs

Combustion of alkanes

Incomplete = carbon monoxide , water , carbon , unburned hydrocarbons

alkane burns with a dirty yellow flame

complete - blue flame

Pollutants due to burning hydrocarbons

1. Carbon dioxide - green house gas

2. Water vapour - green house gas

3. Carbon monoxide - toxic , odourless gas. Absorbed by blood reduces ability to carry oxygen.

4. Carbon - particles causes difficulty breathing , cancer

5. Oxides of nitrogen - photochemical smog and acid rain

6. Sulphur dioxide - acid rain

Catalytic converter of nitrogen

1) removal of carbon monoxide and nitrogen monoxide

2NO +2CO = N2 + 2CO2

2) oxidation of unburnt hydrocarbons

Flue gas desulphurisation

Calcium oxide / calcium carbonate and oxyge reacts with sulfur dioxide

Oxides to make calcium sulphate/gypsum

Free Radical Substitution of Alkanes

Termination - 2 radicals make one molecule with no radicals.

fluorine - least reactive / strongest bond electronegativity decreases so polarity of bond decreases

Ozone formation