C9: Organic Chemistry - Crude Oils + Fuels

How does fractional distillation work

Heated and vaporised: Crude oil is heated until it evaporates into a gas.

Enters the column: The hydrocarbon vapors enter the bottom of the fractionating column.

Temperature gradient: The column is hot at the bottom and cooler at the top.

Vapors rise: The gas vapors rise up the column.

Condensation: The hydrocarbons condense back into liquids when they reach their boiling points.

Different boiling points: Long-chain hydrocarbons have high boiling points and condense near the bottom.

Short-chain hydrocarbons: Short-chain hydrocarbons have low boiling points and condense near the top.

Collection: The liquids are collected at different levels as separate fractions.

Smallest alkane name

Methane

what is the molecular formula for methane

CH4

What is the structural formula for methane

CH4

Second Smallest alkane name

Ethane

Molecular formula: ethane

C2H6

Structural formula: ethane

CH3CH3

Third smallest alkane

propane

Molecular Formula: propane

C3H8

Structural formula:propane

CH3CH2CH3

What is the largest alkane need to know

Butane

Molecular formula: butane

C4H10

Structural formula: butane

CH3CH2CH2CH3

Alkanes formula

CnH2n+2

Alkenes formula

CnH2n

Conditions for thermal/steam cracking

high temps and high pressures, 750deg.C

Conditions for catalytic cracking

low temps + low pressures, zeolite catalyst, 500 degC

What is catalytic cracking used more in?

In industry in production of petrol

Smallest alkene

ethene

Molecular formula: ethene

C2H4

Structural formula: ethene

CH2CH2

Second smallest alkene

propene

Molecular formula: propene

C3H6

Structural formula: propene

CH2CHCH3

3rd smallest alkene

butene

Molecular formula: butene

C4H8

Structural formula: butene

CH2CHCH2CH3

largest alkene

pentene

Molecular formula: pentene

C5H10

Structural formula: pentene

CH2CHCH2CH2CH3

Bromine alkene test

bromine turns orange to colourless if alkene present

Why does bromine change colour if alkene present

Alkenes are unsaturated --> can add bromine --> colourless

what are polymers

plastic made from alkenes

What happens in polymerisation

double bonds break and the carbons are added together. The end bonds have to be left OPEN