Chemistry Alcohols and Alkenes

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  • Created by: A.sx
  • Created on: 08-03-17 16:03
What is it meant by the term functional group?
A group of atoms responsible for the characteristic chemical reactions of a molecule.
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What is the general formula for aliphatic groups with one OH group only
CnH(2n+2)O
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What is the OH group named as?
It is named as a suffix
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Physical properties of alcohols: Boiling points/Volatility
Alcohols make hydrogen bonds with water molecules and with each other because they have H bonded to an electronegative O. Hydrogen bonds between alcohol molecules reduces their volatility (the ease of conversion from liquid to gas)
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Why does ethane have a lower boiling point than ethanol?
Ethanol has hydrogen bonding which is stronger and takes more energy to overcome induced dipole dipole forces in ethane.
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Why is there an increase in the boiling point of the alcohols as chain length increase?
As the carbon chain increases, there are more electrons and greater surface contact. Therefore stronger induced dipole-dipole forces so more energy is required to overcome these forces.
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Solubility in water
Alchols are water soluble because they form hydogen bonds with water
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Why does solubility decrease as the hydrogen carbon chain increases in size?
This is because the OH group has less influence and the solubility of the larger hydrocarbon chain becomes more dominant
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What does miscible mean (not a key definition)
Miscible refers to the ability of a liquid to completely dissolve in another liquid solution
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Classifying Alcohols- Primary Alcohols
The -OH group is attached to a C with at least two H atoms on it and one alkyl group
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Classifying Alcohols- Secondary Alcohols
The -OH group is attached to a carbon atom with only one H atom on it and two alkyl groups
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Classifying Alcohols- Tertiary Alcohols
The -OH group is to a carbon atom with no H atoms on it and three alkyl groups
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What is combstion?
It is when alcohols burn in excess oxygen to produce carbon dioxide and water
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What does dehydration mean? (Not a key definition)
Dehyrdration means to remove water from one molecule.
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What is a good dehydrating agent for alcohols
A good dehydrating agent is concentrated sulphuric acid or concentration Sulfuric acid
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What are the conditions of dehydrating an alcohol & what happens?
The conditions are: heat under reflux. Then an alkene is made. This reaction is described as an elimination reaction because H and OH are being taken out from two adjacent C atoms to make water.
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What agents can be used to oxidise primary and secondary alcohols?
Primary and secondary alcohols can be oxidised using oxidising agents: potassium dichromate, Kr2Cr2O7 in dilute sulfuric acid, H2SO4
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What can a primary alcohol be oxidised to first?
Primary alcohols are oxidised (loss of H) to aldehydes
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What does a primary alcohol oxidise to if the oxidising agent is used in excess?
In a primary alcohol if the oxidising agent is used in excess, further oxidation can occur to give a carboxylic acid
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What do you do when you add an oxidising agent to a primary alcohol?
You would distill this mixture so that the lower boiling point aldehyde (no H bonds made) distils out of the reaction mixture as it forms.
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In a primary alcohol, if acidified potassium dichromate was used as the oxidisng agent; what would the colour change be?
The colour change would be from orange to green in this reaction because dichromate is being reduced to chromium(III)
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In the oxidation of a primary alcohol; what do you do if the oxidising agent is used in excess?
If the oxidising agent is used in excess further oxidation can occur to give a carboxylic acid. You would reflux this so that any aldehyde initially made goes back into the flask to be further oxidised
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What are secondary alcohols oxidised to?
Secondary alcohols can be oxidised in a similar way to primary alcohols to form ketones via reflux.
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Does further oxidation occur in secondary alcohols?
No, because ketones cannot be oxidised as there is no H left on the C
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Can a teriary alcohol be oxidised?
No, tertiary alcohols cannot be oxidised
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Summarise how primary alcohols react with acidified potassium dichromate under reflux
Oxidation to the aldehyde (distillation) and then the carboxylic acid occurs (reflux)
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Summarise how secondary alcohols react with acidified potassium dichromate under reflux
Oxidation to the ketone occurs (reflux)
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Summarise how tetiary alcohols react with acidified potassium dichromate under reflux
No oxidation occurs
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What do alcohols form when they react with hydrogen halides?
Alcohols can form haloalkanes when they react with hydrogen halides.
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How is a hydrogen halide genereated in situ (in place)?
For example, an alcohol is heated, under reflux, in the presence of sodium chloride and sulfuric acid, hydrogen chloride forms in situ. The HCl made then reacts with the alcohol
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Other cards in this set

Card 2

Front

What is the general formula for aliphatic groups with one OH group only

Back

CnH(2n+2)O

Card 3

Front

What is the OH group named as?

Back

Preview of the front of card 3

Card 4

Front

Physical properties of alcohols: Boiling points/Volatility

Back

Preview of the front of card 4

Card 5

Front

Why does ethane have a lower boiling point than ethanol?

Back

Preview of the front of card 5
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