CH4 - Alcohols & Phenols

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By what reaction are alcohols produced?
Nucleophilic substitution of halogenoalkanes.
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In what other way can alcohols be formed?
By the reduction of the carbonyl group.
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What are carbonyl compounds divided into?
Aldehydes and Ketones
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Where, in an aldehyde, is the carbonyl compound positioned on the carbon chain?
At the end (no numbers are needed when naming them).
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What compounds are formed from the reduction of aldehydes?
Primary alcohols
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What are the conditions for the reduction of an aldehyde?
NaBH4 (aq) or anhydrous LiAlH4(aq) / Warm
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Where, in a ketone, is the carbonyl compound positioned on the crarbon chain?
Mid chain - therefore a number is needed when naming them.
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What compound is formed by the reduction of ketones?
Secondary alcohols
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What are the conditions for the reduction of a ketone?
NaBH4 (aq) or anhydrous LiAlH4(aq) / Warm
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Example for reducing a ketone - Formation of pentan-2-ol from pentan-2-one
CH3COCH2CH2CH3 + 2H ----> CH3CH(OH)CH2CH2CH3
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Example for reducing an aldehyde - Formation of pentan-1-ol from pentanal
CH3CH2CH2CH2CH0 + 2H ----> CH3CH2CH2CH2CH2OH
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What is the overall equation for the halogenation of alcohols?
R-OH + HX ----> R-X + H2O
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What are the conditions for the halogenation of alcohols?
HX is generated 'in situ' by adding NaX/KX to a concentrated acid and warming.
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What two compounds can react with alcohols to form esters?
Acyl chlorides and carboxylic acids
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What are the conditions for esterification?
Concentrated H2SO4 acid (catalyst and refflux with the alcohol.
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What is the general equation for esterification?
RCOOH + R'OH ----> RCOOR' + H2O
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Describe an acyl chloride.
They are derivatives of carboxylic acids where the OH group has been replaced by a chlorine.
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What are the conditions for esterification with an acyl chloride?
Add the acyl chloride to the alcohol at room temperature.
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What is the general equation for the esterification of an acyl chloride?
R-COCl + R'OH ----> RCOOR' + HCl
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What do the names of esters incorporate?
Names of the parent alcohol and the parent carboxylic acid or acyl chloride.
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Give the name of the ester that would form with ethanol and propanoic acid.
Ethyl propanoate
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Give the name of the ester that would form with ethanol chloride and ethanol.
Ethyl ethanoate
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Give the name of the ester that would form with methanol and butanoic acid.
Methyl butanoate
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What does dehydration involve?
The elimination of a molecule of water to form an alkene
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What are the conditions for the dehydration of an alcohol?
Heat with concentrated H2SO4 or Heat with concentrated H3PO4 or Pass alcohol vapour over heated catalyst (e.g. aluminium oxide).
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In oxidation, what does the oxidation product depend upon?
Oxidation product depends on the type of alcohol (primary or secondary) and the conditions used.
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What are the conditions for oxidising a primary alcohol firstly to an aldehyde?
Warm / Acidified potassium dichromate solution / Distill off the aldehyde as it forms.
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What is the general equation for the oxidation of a primary alcohol to an aldehyde?
RCOH + [O] ----> RCHO
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What conditions are required to further oxidise the aldehyde to form a carboxylic acid?
Reflux & Excess acidified potassium dichromate solution (oxidising agent).
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What is the overall reaction to form a carboxylic acid from a primary alcohol?
RCH2OH + 2[O] ----> RCOOH + H2O
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What are secondary alcohols oxidised to?
Ketones
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What are the conditions for the oxidation of secondary alcohols?
RCH(OH)R' + [O] ----> RCOR' + H2O
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What type of alcohol cannot be oxidised by heating with acidified potassum dichromate?
Tertiary alcohols
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What are the three main uses of ethanol?
Alcoholic drinks / Industrial solvent / Fuel
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Whainto ethanol using yeastt are biofuels?
Renewable fuels from organic material (e.g. plants).
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What process allows ethanol to be used as an alternative to petrol?
Sugars from plant materials can be fermented into ethanol using yeast in the absence of oxygen at a temperture between 25 and 40 degrees.
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What is the equation for the fermentation of glucose?
C6H12O6 ----> C2H5OH + CO2
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What will eventually form if air is introduced to the process of fermenting plant sugars into ethanol?
Ethanoic acid (because it would become oxidised).
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What are the benefits of using biofuels?
Reduced amount of fossil fuels being burned / Can be considered as a renewable resource because they come from plant material / Considered as 'carbon neutral'.
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What is the equation for the complete combustion of ethanol?
C2H5OH + 3 O2 ----> 2 CO2 + 3 H2O
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Why are biofuels consideredd to be carbon neutral if the combustion of alcohols produces CO2?
There is no change in atmospheric CO2 levels because the CO2 produced during combustion was taken in during photosynthesis.
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What are some drawbacks of using biofuels? (Give 2)
They are not necessarily carbon neutral if you consider planting growing, harvestng etc. / Food shortages caused by farmland being used for fuel instead / destruction of natural habitiats.
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What are phenols?
Compounds that contain an OH group directly bonded to a benzene ring. (Simplest phenol is therefore 'phenol' itself).
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What are the other 2 names for phenol?
Carbolic acid or Hydroxybenzene
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How soluble is phenol in waterVDW?
Sparingly soluble
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Why is phenol only sparingly soluble in water?
The OH group bonds with the water molecules but the benzene ring is non-polar so the presence of the benzene ring reduces the solubility of phenol because it can only form weak VDW forces
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In aqueous solution aliphatic alcohols are neutral. What is the difference with phenol?
Phenol is weakly acidic
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When phenol is acting as an acid, how is the phenoxide ion stabilised?
By the incorporation of a lone pair of electrons of O- into the delocalised pi orbital of the benzene ring
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What salts form when phenol is used to neutralise bases?
Phenoxides
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Complete the equation - Acid + Alkali ----> ?
Salt + Water
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Complete the equation - Acid + Metal ----> ?
Salt + Hydrogen
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Why does phenol undergo electrophilic substitution far more readily than benzene?
O atom of the OH group has 2 lone pairs of electrons in p orbitals that are partially delocalised in the benzene ring. This increases electron density of the pi orbitals and makes the whole molecule more reactive to electrophiles.
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What is the 'activation of the benzene ring'?
When phenol undergoes electrophilic substitution reactions
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What forms when aqueous phenol is shaken with orange bromine water?
Bromine water decolourises and the white, cloudy precipitate of 2,4,6-tribromophenol forms
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How are aliphatic alcohols esterified?
By reaction with carboxylic acids with concentrated sulfuric acid as the catalyst
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How do you distinguish between alcohols and phenols?
Adding orange FeCl3 to a compound containing a phenolic group will result in an intense violet, blue or green compound.
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What colour is seen when phenol itself is added to orange FeCl3?
A violet colour is seen
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What happens if an alcohol is added to orange FeCl3?
No reaction
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Card 2

Front

In what other way can alcohols be formed?

Back

By the reduction of the carbonyl group.

Card 3

Front

What are carbonyl compounds divided into?

Back

Preview of the front of card 3

Card 4

Front

Where, in an aldehyde, is the carbonyl compound positioned on the carbon chain?

Back

Preview of the front of card 4

Card 5

Front

What compounds are formed from the reduction of aldehydes?

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