AS Level Chemistry AQA Unit 1 Section 4: Organic Chemistry

A breif overview on the topics in Unit 1 Section 4 of AQA's As Chemistry Course. Notes based on CGP Revision Guide.

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Formulas and structural Isomerism

Their of 5 different types of formula which you need to know:

General :An algerbraic formula that tells you how many of each atom is in any compound of  that type.

eg.  C(n) H(2n+2)

Empiricla formula: The simplest ration of atoms in a compound.

eg. C(2) H(5)

Molecular Formula: The actual number of atoms in a compound.

eg. C(4) H(10)

Structural Formula: Shows the astoms carbon by 

carbon with the attached hydrogen's and othe atoms (eg iodene, chlorine) and the functional group.

eg. CH(3)CH(2)CH(2)CH(3)

Displayed Formula: Shows the arrangement of the atoms and the bonds between them.

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Structural Isomers

Three Different Types:

Chain Isomers: Different arrangement of the carbons so that the longest chain is shorter with chains coming from it. 

Positional Isomers: Have the same carbon chain and the same atoms but the differance is that some atoms are attached to differnet carbons. 

Eg. A Chlorine atom moving from C(2) to C(3)

Functional Group Isomers

Have the same atoms arranged into different function groups. 

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Alkanes

Are saturated hydrocarbons with the general formula C(n)H(2n+2).

Every Carbon has its maximum n umber of 4 bonds and they cant make any more so an alkane is saturated. 

Cycloalkanes are a ring of carbons each with 4 bond.s 2 to other carbons and 2 to hydrogen's. These have the formula C(n)H(2n) as there are no "end" carbons as it is in a chain but it is still an alkane. 

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Crude Oil.

Crude oil is separated using fraction distillation. This heavier compounds will stall further down the column and the lighter ones will go to the top. This is because smaller hydrocarbons have a lower boiling point. The different sized compounds are piped out of the tower at the different levels based on their boiling points and then bottled and sold. 

It takes 350 degrees C to vapourise the crude oil.

The smallest hydrocarbons dont condense at all and are tapped off as a gas.

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Cracking.

Fairly simple concept- Longer less useful hydrocarbons are intensely heated up to 1000 degrees C so that one or more of the C-C bonds break and you are left with 2 or more shorter more useful and thus more valuable Hydrocarbons. 

Cracking can also be carried out by catalytic cracking which entails using zeolite catalyst at half the temperature of thermal cracking to achieve the same thing. 

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Fuels

Alkanes are used as fuels. If a fuel burns incompletely it will produce Carbon Monoxide. This is dangerous to health and the environment but will only happen if the oxygen supply is limited.

Complete combustion for alkanes:

C(3)H(8) +5O --> 3CO(2) + 4(2)O

This equation will stand for every alkane except the quantities of each atom and compound will change. 

Incomplete combustion of Alkanes:

CH(4) +1.5 O(2) --> CO + 2H(2)O

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Environmental Effects.

Greenhouse gasses stop some heat from the sun from escaping from our atmosphere. This keeps the earth warm causing global warming. These gasses include: Co2, CO, SO2 etc

CO2 is the main greenhouse gas. 

Burning fossil fuels produces this and is thus Bad. 

The increase in temperature of our plant has increased a the amount of CO2 we have been producing increases. 

Sulfur Dioxide produces acid rain which corrodes marble monuments etc. 

Methane is a greenhouse gas produced from rotting rubbish and cows etc. 

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Comments

JassiiOo

tHis is really helpful thnx (:

Alex James Thomas

JassiiOo wrote:

Gland to hear :)

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