A group of organic compounds where the parent functional group is (-OH)
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What is Infrared Spectroscopy?
A technique used that utilises a substances behaviour on absorbing IR radiation, and then produces a spectrum that can identify certain functional groups
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What is Reflux?
Continuing to boil and condense a reaction mixture to ensure that the contents of the flask don't boil dry.
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Primary alcohol
Has the functional group attached to a carbon atom with no more than one alkyl group
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Secondary alcohol
Has the functional group attached to a carbon atom with two alkyl groups
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Tertiary alcohol
Has the functional group attached to a carbon atom with three alkyl groups
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Why are small alcohols soluble in water?
Dipole-dipole and hydrogen bond intermolecular forces pull the molecules apart from one another. They have OH groups which make them polar. The positive and negative dipoles align and cause the alcohol molecules to break apart from each other in the
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As the size of the alcohol increases, the solubility decreases. Explain why
The hydrocarbon chains are forcing their way between water molecules and so breaking hydrogen bonds between those water molecules. As size increases, the dipole-dipole forces increase and therefore more energy is required to break them.
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What is the first rule of naming an alcohol?
Find the longest continuous chain of carbon atoms - this provides the last part of the name
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What is the second rule of naming?
Identify any side groups or branches and name them. The parent alkane changes from "ane" to "yl"
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Formula for an alkyl group?
CnH2n+1
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What is the third rule of naming?
If necessary, identify the number of the C atom to which the side chain is attached
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What takes priority in the order of an alcohol name?
The alphabet
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Aliphatic molecules contain carbon atoms joined as..?
Straight chains, branched chains, non-aromatic rings such as cyclohexane
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What does homologous mean?
Members of a chemical family which differ by a -CH2- group. eg methanol to ethanol to propanol etc
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What is the part of the molecule where most chemical reactions take place?
The functional group
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What happens when alcohols are oxidised?
They are added to acidified dichromate. A colour change from orange/yellow to blue/green occurs.
alcohol = aldehyde. alcohol = carboxylic acid. Reflux is used in order to ensure that the alcohol is fully oxidised to the carboxylic acid.
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Oxidation of secondary alcohols
alcohol = ketone
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Properties and reactions of alcohols
Alcohols are colourless liquids with distinctive smells. Smaller alcohols are freely soluble in water due to creating hydrogen bonds. Larger alcohols are insoluble. Boiling points are high due to hydrogen bonding.
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Alcohol combustion reaction
Alcohols burn readily with a blue flame to form CO2 and H2O
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Dehydration/elimination to form an alkene
A water molecule is 'eliminated' from an alcohol molecule. The reaction is carried out by passing the alcohol over hot Al2O3 and refluxing the alcohol with conc H2SO4
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How to identify an alkene
Br2 water is used to detect alkenes in the lab, a colour change takes place which is orange/brown to colourless
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To work out the identity of an unknown compound we need to piece together information from several sources:
% composition shows the empirical formula, the mass spectrum shows the relative molecular mass. RMM and empirical formula shows the molecular formula.
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What are the masses of: CH3 and CH3CH2?
CH3 = 15, CH3CH2 = 29
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What does the infrared spectrum allow us to identify?
Some of the bonds and groups in the molecule
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What are haloalkanes?
alkane molecules which have had one or more H atoms replaced by a halogen atom. Can be formed from alcohols in a reaction known as a 'substitution reaction' - the OH of the alcohol is substituted for a halogen atom.
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Uses of infrared spectroscopy?
Used in breathalyzers which gives an indication of the amount of alcohol in breath. Monitor air pollution from car pollution, look for carbon monoxide and nitrogen oxide
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Conditions to produce a haloalkane?
Generated in 'situ': heat is needed and the haloalkane is distilled off as it forms
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Other cards in this set
Card 2
Front
What is Infrared Spectroscopy?
Back
A technique used that utilises a substances behaviour on absorbing IR radiation, and then produces a spectrum that can identify certain functional groups
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