AQA Chemistry (AS): Introduction to Organic Chemistry

Introduction to organic chemistry, including the homologous series, naming molecules, formulae of organic compounds, fractional distillation of crude oil and car chemistry.

Have tried to crop the info down as much as possible and includes all relevant facts.

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Formulae of Organic Compounds

Number of carbons (Prefix): 1 (Meth-), 2 (Eth-), 3 (Prop-), 4 (But-), 5 (Pent-), 6 (Hex-), 7 (Hept-), 8 (Oct-), 9 (Non-), 10 (Dec-)

This applies to organic compounds.

-ane if it is a single bond

-ene if it is a double bond

What is an isomer? - A compound with the same molecular formula but different structural formula.

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Making alkanes and describing a homologous series

[Was unable to put hydrogens around these, but in real diagrams hydrogen atoms are present]

C-C-C-C-C-C-C This is heptane, as there are 7 carbons. It is a straight chain molecule.

C-C-C-C-C-C-C if there is another carbon brancing off from one of these carbons, then it will be methylheptane. depending on which carbon it branches off from depends on the number which goes before it. For example if the branch is second carbon from the left then the name would be 2, methylpentane.Even with 8 carbons it is still "hept" because the longest chain has 7 carbons, and the name is based on the longest chain.

C-C-C-C-C-C-C if there are 2 branches of carbons then it will be "dimethyl" and if there are 3 branches then it will be "trimethyl" etc.

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Important facts about the homologous series

As more branches appear on the molecules, instead of having a straight chain, the boiling point decreases because the Van Der Waals forces decrease.

However, the higher the mass, the stronger the inter-molecular forces become therefore more energy is required each time to break those inter-molecular forces.

The homologous series- family of hydrocarbons, mass goes up by the same increment.

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There are 2 types of cracking:

Thermal - 450-800 degrees C, free radical mechanism, high percentage of alkenes

Catalytic- lower temp used, zeolite catalyst, carbocation mechanism, small branced alkanes and aromatic hydrocarbons (benzene compounds)

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Complete and Incomplete combustion

Complete Combustion Alkanes (hydrocarbons) MAKES (with excess O2) Water + Carbon dioxide

Incomplete Combustion -Limited supply of oxygen, carbon monoxide and water produced

Carbon is also made.

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Fractional distillation of crude oil

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Very helpful, thankyou :)

Majeed Abdul


you spelt branched rong

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