Alcohols Flashcards
What is the functional group in alcohols?
Hydroxyl group
-OH
What is the general formula for alcohols?
CnH2n+1OH
What are the different types of alcohols?
Primary
Secondary
Tertiary
What is a primary alcohol?
An alcohol where the carbon attached to the hydroxyl group is attached to 1 other alkyl group
What is a secondary alcohol?
An alcohol where the carbon attached to the hydroxyl group is attached to 2 other alkyl groups
What is a tertiary alcohol?
An alcohol where the carbon attached to the hydroxyl group is attached to 3 other alkyl groups
What are the properties of alcohols?
Low volatility
High boiling points
Why do alcohols have high boiling points?
They have hydrogen bonding
How can alkenes be made using alcohols?
Alkenes can be mad by eliminating water in alcohols in a dehydration reaction
What is the general formula for dehydration of alcohols?
CnH2n+1OH → CnH2n + H2O
What does this reaction allow to happen?
It allows for alkenes to be produced from renewable resources.
Therefore, polymers can be made without the need for oil.
What is one of the main industrial uses for alkenes?
It is used as a starting material for polymers
What is the equation for the dehydration of ethanol?
C2H5OH → C2H4 + H2O
concentrated sulfuric acid and phosphoric acid are used as catalyts for this reaction
How can alcohols be produced from alkenes?
Alcohos can be produced by the hydration of alkenes in the presence of an acid catalyst.
How can ethanol be produced?
Ethanol can be produced by the hydration of ethene
What is the equation for the hydration of ethene
C2H4 + H2O → C2H5OH
What are the conditions for the hydration of ethene?
concentrated phosphoric acid
300 degrees
60 atm
What are the advantages of producing ethanol by hydration of ethene?
Faster reaction
Continuous process
Lower labour costs
Ethanol produced is 99.9% pure
What are the disadvantages of producing ethanol by hydration of ethene?
Non-renewable source of ethene
Expensive initial costs
Higher temperatures and pressures
How can ethanol be produced?
Ethanol can be produced by fermentation of glucose
What is the equation for fermentation of glucose?
C6H12O6(aq) → 2C2H5OH(aq) + 2CO2(g)
What are the conditions for fermentation of glucose?
zymase(yeast) anaerobic warm aqueous 30-40 degrees
What are the advantages of fermentation to produce ethanol?
Sugar is renewable
Cheap
Lower temperatures and pressures
What are the disadvantages of fermentation to produce ethanol?
Slow Batch process Ethanol produced is impure Purification by distillation needed Higher labour costs Land could be used to grow food crops
Ethanol produced using the fermentation method is considered a biofuel.
What is a biofuel?
A biofuel is a fuel that’s made from a biological material that’s recently died
Why can the fermentation method be considered carbon neutral?
The carbon dioxide produced is equal to the carbon dioxide absorbed during photosynthesis
What are the equations that show that there is no net contribution to CO2?
Photosynthesis: 6CO2+ 6H20 → C6H12O6 + 6O2
Fermentation : C6H12O6 → 2C2H5OH + 2CO2
Combstion: 2C2H5OH + 6O2→ 4CO2 + 6H2O
Why is ethanol production by fermentation of glucose, not carbon neutral?
The ethanol produced has to be fractionally distilled
Powering of machinery
Transportation of the ethanol
What affects how much an alcohol can be oxidised?
The structure of the alcohol
What is the oxidising agent used to oxidise alcohols?
Acidifed potassium dichromate(VI)
K2Cr2O7
What can be observed when the acidified potassium dichromate oxidises the alcohols?
The orange dichromate(VI) ion(Cr2O7^2-) is reduced to the green chromium ion(Cr^3+)
What are primary alcohols oxidised to?
Aldehydes and then carboxylic acids
What are secondary alcohols oxidised to?
Ketones
What are tertiary alcohols oxidised to?
They can’t be oxidised
What is an aldehyde?
It is a carbonyl group with a hydrogen and one alkyl group attached to the carbonyl carbon atom
What is a ketone?
It is a carbonyl group with two alkyl groups attached to the carbonyl carbon atom
What is the functional group of aldehydes and ketones?
C=O
What is the general formula of aldehydes and ketones?
CnH2nO
What is the suffix for aldehydes?
-al
What is the suffix for ketones?
-one
What is the functional group of carboxylic acids?
COOH
What is the general formula of carboxylic acids?
CnH2n+1COOH
What is the suffix for carboxylic acids?
-oic acid
What are the conditions for oxidising primary alcohols to aldehydes?
Excess alcohol
Warm gently
Distillation
What is the general formula for the partial oxidation of primary alcohols?
Primary alcohol + [O] → Aldehyde + water
What are the conditions for the oxidation of aldehydes to carboxylic acids?
Excess acidified potassium dichromate
Heat under reflux
What is the general formula for the oxidation of aldehydes to carboxylic acids?
Aldehyde + [O] → Carboxylic acid
What are the conditions for oxidising secondary alcohols into ketones?
Heat under reflux
Excess acidified potassium dichromate
What is the general formula for the oxidation of secondary alcohols?
Secondary alcohol + [O] → Ketone + water
How can we distinguish between ketones and aldehydes?
We can use:
Tollen’s reagent
Fehling’s/Benedicts’s solution
What is Tollen’s reagent
Ammoniacal silver nitrate
What is Fehling’s/Benedict’s solution?
Solutions of deep blue Cu2+ ions
What would happen if we used Tollen’s reagent to distinguish between ketones and aldehydes?
Aldehydes would form a silver mirror (the silver ions have been reduced to silver atoms)
Ketones would show no visible change
What would happen if we used Fehling’s/Benedict’s solution to distinguish between ketones and aldehydes?
Aldehydes would form a brick-red precipitate of Cu2O(copper ions have been reduced to copper(I) oxide
What would be the equation for the reaction between ethanal and Tollen’s reagent?
CH3CHO + 2Ag+ + H2O → CH3COOH + 2Ag + 2H+
What would be the equation for the reaction between ethanal and Fehling’s/Benedict’s solution?
CH3CHO + 2Cu^2+ + 2H2O → CH3COOH + Cu2O + 4H+
