Topic 15: Alcohols Flashcards
Alcohols
-OH functional group
Fermentation
Makes ethanol from glucose
Hydration of ethene
Adding steam to an alkene to produce an alcohol
Fermentation equation
C6H12O6 —> 2C2H5OH + 2CO2
Fermentation conditions
Yeast, oxygen free environment, 30-40*C
Fermentation advantage
Sugar is renewable
Cheap equipment
Fermentation disadvantage
Batch process
Ethanol needs distilling to purify
High labour costs
Hydration of ethene equation
C2H4 + H20 <===> C2H5OH
Hydration of ethene conditions
CONC. H3PO4 or CONC. H2SO4
temp 300*C
pressure 70atm
Hydration of ethene advantages
Continuous
Purer product
Hydration of ethene disadvantages
Ethene is non renewable - from crude oil
High equipment cost
Low labour cost
Biofuel
Fuel from plants
Ethanol as biofuel
Photosynthesis takes in 6 CO2 when the glucose produced is fermented to ethanol and combust 6 CO2 produced so no net release of CO2 so carbon neutral
Photosynthesis reaction
6CO2 + 6H2O —> C6H12O6 + 6O2
Ethanol combustion reaction
2C2H5OH + 6O2 —> 4CO2 + 6H20
Ethanol as a fuel 100% carbon neutral
No
Transport produces CO2
Machines produce CO2
Primary alcohol oxidises into
Aldehyde and further to carboxylic acid
Tertiary alcohol oxidises into
Can’t be oxidised
Secondary alcohol oxidises into
Ketone
Oxidising agent for alcohols
Acidified potassium dichromate
K2Cr2O7
Test for aldehyde and ketone and alcohols
Aldehyde, primary and secondary alcohols turn orange to green when oxidised using acidified potassium dichromate. Ketones and tertiary alcohols wont.
Oxidation reaction of primary alcohol equation
C2H5OH + [O] —> CH3CHO + H2O
Oxidation reaction of primary alcohol further equation
CH3CHO + [O] —> CH3COOH
Producing only aldehyde from primary alcohol
Heat and distil - will evaporate and condense into new flask
Producing carboxylic acid from primary alcohol
Heat under reflux - will evaporate and condense back into original pear shaped flask then distil the carboxylic acid
Oxidation of secondary alcohol equation
CH3CHOHCH3 + [O] —> CH3COCH3 + H2O
Test for aldehyde
Add Tollens reagent to aldehyde silver mirror will form wont with ketone as can’t be further oxidised
Test for aldehyde (other)
Add Fehling’s solution orange ppt for aldehyde nothing for ketone stays blue
Dehydration of ethanol equation
Ethanol —> ethene + water
Dehydration of ethanol what happens?
Hydroxyl group is removed along with a hydrogen from the adjacent carbon NOT the one attached to the hydroxyl group
Dehydration of tertiary alcohol
Can’t happen, no H to remove from adjacent C
Conditions and type of reaction of dehydration of alcohol
conc. H2SO4 elimination reaction
Mechanism of dehydration of ethanol
Partial charges on hydroxyl group
Arrow from lone pair to H+
New molecule
Arrow from adjacent CH bond to CC bond
Arrow from CO bond to positive O attached to 2 H
Creates ethene and water
Hydration of ethene mechanism
Arrow from double bond of ethene to H+.
New molecule
Carbocation made
Arrow from lone pair on water molecule to carbon
New molecule
Positively charged water attached to molecule
Arrow from O-H bond to oxygen
Makes alcohol and H+
