Organic chemistry up to pg 63

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  • Created by: Hannah
  • Created on: 26-04-13 13:20
Define nomenclature
Naming of an organic compound
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What is a chain isomer?
The carbon skeleton can be arranged in a straight chain or branched chain
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What is a positional isomer
The skeleton and the functional group could be the same, with the group attached to a different carbon
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What is a functional group isomer?
The same atoms can be arragned into different functional groups
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What is a stereoisomer?
Same structural formula but a different arrangement in space
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Why do some alkenes have sterioisomers?
As they have lack of rotation around the double C=C bond
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What is an E-isomer? (or trans)
Where the two functional groups are on opposite sides of the C=C bond
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What is a Z-isomer? (cis)
When the same groups are on the same side of the C=C bond
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Why can't you use cis/trans system when there are more than 2 different groups?
As there are more than 2 it could be any of cis/trans. You have to use E/Z and decide which group has a higher priority
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What is the equation for %age yeild?
Actual yeild/theoretical yield x 100
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What is the equation for atom economy?
Mr or desired product/ Mr of all products x 100
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Why is it good to have a high atom economy?
Less waste prouced, it costs money to seperate desired products from waste products, materials cost a lot of money, so less waste produced less money wasted, low atom economy= less sustainable
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What are the atom economies for addition reactions?
Always 100% since no atoms are wasted
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What is the general formula for alkanes?
CnH2n+2
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Define sasturated hydrocarbon
A molecule made of carbon and hydrogen only which has no double bonds
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What shape are alkanes?
Tetrahedral
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What would have a larger boiling point a branched alkane or a straight chained alkane?
Straight chained alkane as they can 'pack' in more closely, therefore have stronger Van der Waals forces due to more surface contact
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What state are smaller alkanes at room temperature?
Gas- they've got low boiling points
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What state are larger alkanes at room temperature?
Liquids- they've got higher boiling points
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What state do alkanes have to be in before being combusted?
Gas (have to be vaporised)
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What type of alkanes vaporise quickly?
Smaller alkanes- they're more volatile- they burn easily too
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What does combustion (in enough oxygen) of alkanes produce?
CO2 + H2O
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What does combustion (in limited oxygen) of alkanes produce?
CO + H2O
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What types of alkanes release more energy per mole?
Larger alkanes
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Why is CO (carbon monoxide) bad?
CO is better at combining with haemoglobin than O2, so if you breathe in air with a larger conc. of CO then more CO will be taken around the blood, causing oxygen deprivation
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What is petroleum/ crude oil made of?
Different sized alkanes
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What is the process called when you seperate crude oil into fractions?
Fractional distillation
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What are the conditions for fractional distillation?
Crude oil has be vaporised at bout 350C
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How does fractional distillation happen?
Vaporised crude oil goes into fractioning column. Largest hydrocarbons don't vaporise as boiling point is too high, form residue. Each fraction condenses at different temps. Smallest don't condense
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What is a petrochemical?
Any compound made from crude oil and is not a fuel
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Give examples of some 'light fractions'
Petrol, naptha
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What is cracking?
Breaking long-chain alkanes into smaller hydrocarbons- involves breaking C-C bonds
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What is the main way of craking?
Catalytic cracking
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How does catalytic cracking happen?
Heavy fractions are passed over a catalyst at high temp. and moderate pressure. this breaks them into smaller molecules
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Why does using a catalyst cut costs?
Reaction can be done at lower temps. and pressure. Speeds up reaction
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Hydrocarbons with a ____________________ burn more smoothly
High octane rating
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How do manufactures convert straightchain alkanes into branched alkanes?
Isomerisation and reforming
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What happens in isomeriation of straightchain hydrocarbons to branched?
Heat the alkane, with a catalyst stuck on inert aluminium oxide, they break and join up as branched. A zeolite is used to seperate the isomers
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What happens in the reforming of straightchained alkanes to cyclic?
Catalyst of platinum and another metal, stick catalyst on inert aluminium oxide
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Why do we use fossil fuels?
Energy- they're exothermic,used for fuel, transport, generate electricity, make plastics
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What are some alternatives to fossil fuels?
bioethanol- can be used for fuels for cars, produced from plants(fermentation of sugar from maize etc). Biodiesel, ferining fats and oils
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What are some problems with making fuels from plants?
Develpoed countries will create a huge demand, farmland will be used to produce 'fuel' plants, developing countries may not have any food
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What is heterolytic fission?
Where two different subtances are formed, a positive cation and a negative anion
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What is fission?
The breaking of covalent bonds
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Homolytic fission?
Two electrically uncharged radicals. These are very reactive as there is unpaired electrons
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What is the breaking of the bonds in initation called?
photodissociation
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What is a disadvantage of free-radical substitution
You get a mixture of products, the reactions don't stop when you reach the desired product,reactions carry on, you have to have an excess of the reactant
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What molecule is used in free radical substitution?
Alkanes
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What is the general formula of alkenes?
CnH2n
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Why are alkenes unsaturated?
They have a double C=C bond, they can make more bonds in addition reactions
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What is a double bond made of?
Pi bond and sigma bond
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Describe sigma bond
Formed when 2 s orbitals overlap,they overlap on a straight line- gives highest electron density between the nuceli, it is a single covalent bond
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Describe Pi bond
When 2 p orbitals overlap, has 2 parts 'above' and 'below' the molecular axis, dumbbell shaped
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Why are alkenes more reactive than alkanes?
As there are 2 pairs of electrons in the C=C bond, high electron density. The Pi bond sticks out, so is more likely to be attacked by electrophiles
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Why can't double bonds rotate?
As the p orbitals have to overlap to form a Pi bond. C=C double bond and the atoms bonded to these carbons are planar (falt) and rigid (can't bend)
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The carbon skeleton can be arranged in a straight chain or branched chain

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What is a positional isomer

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Card 4

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What is a functional group isomer?

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Card 5

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What is a stereoisomer?

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