it contains the -OH functional group known as the hydroxyl group
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compare the physical properties of alcohols and alkanes
alkanes are non-polar as the electronegativity of C-H are so similar whilst alcohols have a polar O-H because of the difference in electronegativities
alkanes have very weak londons force and so do alcohols but they also have a strong hydrogen bonds
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difference in volatility
Alcohols have a higher boiling point than alkanes and lower volatility
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compare the solubility in water
alcohols are more soluble in water as they have hydrogen bonding and alkanes are non-polar
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how can alcohols be classified
they can be classified as primary, secondary or tertiary depending on the number of hydrogen atoms and alkyl groups attached to the carbon atom that contains alcohol functional group
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what are the two simplest primary alcohols
methanol and ethanol
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what is the combustion of alcohols
the reaction is exothermic and it produces carbon dioxide and water
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what is the test for the oxidation of primary and secondary alcohols
use potassium dichromate with sulfuric acid and if the alcohol is oxidised the orange and will go green
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what is the oxidation of primary alcohols reactions
it can be oxidised to either aldehydes or carboxylic acids
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how you prepare aldehydes
primary alcohols with acidified potassium dichromate and you distil it with potassium dichromate not in excess
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how you prepare carboxylic acid
primary alcohols is heated strongly under reflux, with an excess of potassium dichromate and ensure that the alcohol is fully oxidised and heat under reflux
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what is the oxidation of secondary alcohols
they are oxidised to alcohols to ketones heat under reflux with oxidising mixture with potassium dichromate
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oxidation of tertiary alcohols
they do not undergo oxidation
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what is dehydration
is any reaction in which a water molecule is removed from the starting material.
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dehydration of alcohols
heated under reflux in the presence of an acid catalyst such as conc. sulfuric acid or conc phosphoric acid
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substitution reactions of alcohols
they react with hydrogen halides to form haloalkanes
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what is the reactivity of haloalkanes
halogens are more electronegative than carbon atom which is slightly positive and can attract species containing lone pair of electrons
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what is a nucleophile
they are species that donate a lone pair of electrons
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what are some examples of nucleophiles
hydroxide ions, water molecules or ammonia molecules
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what mechanism can they undergo
they undergo nucleophilic substitution
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which alcohols undergo nucleophilic substitution
primary haloalkanes
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hydrolysis mechanism
the nucleophile OH- approaches the carbon atom attached to the halogen
this direction of attack by OH- minimises repulsion between nucleophile and the slightly negative halogen
a lone pair of electons on the hydroxide ion is attracted and donate to the s
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hydrolysis mechanism (2)
a new bond form between oxygen atoms and of hydroxide and C atoms and the C-Halogen bond breaks with heterolytic fission and alcohol formed and halide formed
you can use NaOH which form alcohol and sodium halide
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hydrolysis and carbon-halogen bond strength
the rate of hydrolysis depends upon the strength of the C-halogen bon in the haloalkane
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trend in hydrolysis of haloalkanes
the rate of hydrolysis increases as the strength of the C-halogen bond decreases
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what practical can be carried out to measure the rate of hydrolysis
set up three test tubes and ethanol and two drops of haloalkane to each then put in water bath at 60 degrees and 1 cm3 of silver nitrate and start the clock and see how quickly ppt forms
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what are the results
the 1-cholorobutane reacts slowest and the C-Cl bond is strongest and 1-iodobutane reacts fastest and C-I bond is weakest
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the ozone layer
CFCs and the ozone layer pg 235
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Other cards in this set
Card 2
Front
compare the physical properties of alcohols and alkanes
Back
alkanes are non-polar as the electronegativity of C-H are so similar whilst alcohols have a polar O-H because of the difference in electronegativities
alkanes have very weak londons force and so do alcohols but they also have a strong hydrogen bonds
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