Alcohols Flashcards
What is the general formula for alcohols?
CnH2n+1OH
Describe the process of fermentation
Extract sugar
Add yeast
Ferment
What are the conditions needed for fermentation?
30-40degrees
CO2 released
Batch process (start + stop)
What is the equation for fermentation?
Glucose —-> ethanol + carbon dioxide
What is the symbol equation for fermentation?
C6H12O6 (aq) —-> 2CH3CH2OH (aq) + 2CO2 (g)
What are the advantages of fermentation?
Sugar = renewable resource
Batch process = cheap
More carbon neutral
What are the disadvantages of fermentation?
Very slow
Impure = needs fractional distillation = takes time + money
High labour costs
Describe the process of hydration of ethene
Extract crude oil
Fractional distillation then cracking
Hydration
What are the conditions needed for the hydration of ethene?
Phosphoric acid catalyst
High temperatures + pressure
Continuous process
What is the equation for hydration of ethene?
Ethene + water —-> ethanol
What is the symbol equation for hydration of ethene?
C2H4 + H2O —-> CH3CH2OH
What are the advantages of hydration of ethene?
Fast
Pure
95% yield
Continuous = cheaper manpower
What are the disadvantages of hydration of ethene?
High tech equipment = expensive initially
High energy costs
Non-renewable
What are the differences between alcohols and alkanes that have the same no. of carbon atoms?
Less volatile
Higher melting point due to H bonding
Greater water solubility
Are methanol and ethanol soluble in water?
YES
Why is ethanol and methanol soluble in water?
H bonds form between the OH group of the alcohol and water molecule
What happens to solubility as chain length increases?
Solubility decreases since influence of OH group decreases
What does classifying alcohols depend on?
No. of H atoms and alkyl groups attached to the carbon atom that contains the alcohol functional group
What must a primary alcohol have?
At least 2 H atoms
1 carbon centre
What must a secondary alcohol have?
1 H atom
2 carbon centres
What must a tertiary alcohol have?
No H atoms
3 carbon centres
What happens to the significance of H bonding as chain length increases and what does this mean?
H- bonding significance decreases and London forces increase
This means gap between B.Pts of alcohols and alkanes narrow
What does an oxidising agent help something to do?
Gain oxygen or lose electrons
What happens to primary alcohols when they are oxidised?
They oxidise to form an aldehyde and water
What does the oxidising agent always take off the alcohol?
Takes a H off the alcohol group and a H off the carbon to produce water
What is the oxidising agent used in the oxidation of alcohols?
Sodium or potassium dichromate (VI)
What is the formula for sodium and potassium dichromate (VI)?
Na2Cr2O7
K2Cr2O7
What must the oxidising agent be in the oxidation of alcohols?
Acidified
What does an oxidising agent do?
Helps things to be oxidised so themselves can be reduced
What colour does the oxidising agent change from?
Orange to green
What happens in the oxidation of an aldehyde?
They oxidise to form a carboxylic acid
The oxygen goes on the H
What is further oxidation?
When an alcohol is oxidised twice to form a carboxylic acid
What is mild oxidation?
When an alcohol is oxidised once to form an aldehyde
What is reflux?
Continuous evaporation + condensation (reactants can’t escape the flask)
What happens in the oxidation of secondary alcohols?
They oxidise to form ketones
What can’t happen to ketones?
They can’t be oxidised further
What happens in the oxidation of secondary alcohols to ensure the reaction is complete?
Alcohol is heated under reflux with oxidising mixture
What happens to the dichromate (VI) ions in the oxidation of secondary alcohols?
Changes from orange to green
What happens in the oxidation of tertiary alcohols?
Nothing they can’t undergo oxidation reactions
What happens to the dichromate (VI) ions in the oxidation of tertiary alcohols?
They remain orange
