Alcohols Flashcards
What is the functional group of alcohols?
What is the suffix and prefix for naming alcohols?
-OH functional group (hydroxyl group) which is bonded to a carbon chain
-ol suffix and hydroxy- prefix
What can alcohols be classified as and what does that depend on?
They can be classified as primary, secondary or tertiary alcohols
This depends on the number of carbon atoms directly attached to the carbon atom attached to the OH group
How do you identify which is a primary, secondary or tertiary alcohol?
Primary - bonded to one other carbon
Secondary - bonded to 2 other carbons
Tertiary - bonded to 3 other carbons
When do alcohols undergo elimination reactions?
What is another name for the reaction and why?
When heated with concentrated sulfuric acid at 450K
Dehydration reaction because water is eliminated
Define dehydration
Dehydration is when water is lost from a compound
What is the difference between a dehydration reaction and a condensation reaction?
In both reactions water is formed however in dehydration the water comes from one molecule whereas in condensation the water comes from 2 molecules
What are 2 ways alcohol can be made in industry?
Direct hydration of Ethene with steam
Industrial Fermentation
What are 3 products that can be used for industrial fermentation?
Sugar cane
Molasses ( a product of refining sugar cane)
Starch (from potatoes or corn)
What is the product of industrial fermentation?
A mixture of water and about 15% ethanol by volume
Why is there a limited amount of alcohol produced with fermentation?
No more alcohol is produced because the yeast is denatured by the alcohol
What is the equation for the fermentation of glucose to form ethanol?
Include the 4 conditions
Glucose (aq) —> 2(ethanol) (aq) + 2(carbon dioxide) (g)
Aqueous solution of glucose
Yeast catalyst at 310K temp
1 atm pressure
Anaerobic conditions
How would you separate the mixture of water and ethanol formed during fermentation?
Fractional distillation
Explain why those conditions are used in fermentation? (3)
High temperatures would denature the enzymes in the yeast
Normal pressure are used as no gases involved in the reaction
If oxygen present this may oxidise the ethanol to ethanoic acid
What can ethanol be used as?
Fuel for cars (Brazil)
What 3 renewable sources can ethanol be made from?
Sugar cane
Corn
Maize
What is ethanol made from renewable sources called
Bio ethanol
What are biofuels
They are fuels made from living (raw materials)
Write a series of equations to support the statement that ethanol produces by fermentation is carbon neutral
Learn the 3 equations !!!!!!!
Slide 29
Why is the ethanol produced by fermentation carbon neutral
The amount of carbon dioxide released is equal to the amount of carbon dioxide absorbed when forming the glucose - this makes it carbon neutral
Define carbon neutral
A process in which net carbon dioxide emission is zero
Why are biofuels not carbon neutral
Give an example
They produce less carbon dioxide overall
Because fossil fuels are used in the production of biofuels
For example in making fertilisers for the growing plants and machinery used to harvest the crops
What is an ethical issue linked to making biofuels
Crops that could be used to feed people are used to provide raw materials for biofuels instead
This could cause food shortages or increases in the price of food
What are 3 economic factors related to the formation of ethanol
Human Resources - more people needed to produce biofuels than are needed to produce petrol and diesel
Increased income - for farmers
Lower fuel prices - biofuels limit the demand for fossil fuels, helping to reduce increases in fuel prices
What are primary alcohols oxidised to and how
Aldehydes by an oxidising agent
For example an aqueous solution of acidified potassium dichromate
What is the symbol for an oxidising agent called
An O in square brackets
What are the 3 definitions for oxidation
Gain of oxygen
Loss of hydrogen
Loss of electrons
How is further oxidation prevented when aldehydes are prepared by the reaction of a primary alcohol with an oxidising agent
The aldehyde is distilled off as soon as it is formed and collected
How can aldehydes be further oxidised to carboxylic acids? (Primary alcohols)
If excess oxidising agent is used and the reaction is done under reflux
How does reflux for carboxylic acids work
Once the aldehyde is formed it is condensed back into the reaction mixture and forced to react further
What are the 2 products of oxidation of primary alcohols
Aldehydes then carboxylic acids
What can secondary alcohols be oxidised to and how
They can oxidised to ketones by using an oxidising agent
(Acidified potassium dichromate)
Why can’t tertiary alcohols be oxidised
What is an exception
There are no hydrogen atoms attached to the carbon bonded to the OH group so no hydrogen can be removed
Under extreme conditions when carbon - carbon bonds are broken
Describe the reaction that gives the basis for testing for primary and secondary alcohols
The reaction of acidified potassium dichromate with alcohols
It is orange but when it reacts with a secondary and primary alcohol it is reduced to chromium (111) ions which are green
However since tertiary alcohols can’t be oxidised by potassium dichromate, it has no effect and does not change colour
What functional group do aldehydes, ketones and carboxylic acids all contain
The carbonyl functional group C = O
What is the suffix for aldehydes, ketones and carboxylic acids
Aldehydes -al
Ketones -one
Carboxylic acids -oic acid
How can aldehydes and ketones be distinguished and why
They can be distinguished using a
mild oxidising agent
The presence of the C-H bond in aldehydes allows aldehydes to be oxidised to carboxylic acids so aldehydes are mild reducing agents
What is Tollen’s Reagent?
It is ammonical silver nitrate
[Ag(NH3)2]NO3
Simplified to [Ag(NH3)2]+
How can Tollen’s Reagent be used to test for aldehydes / ketones?
A reaction is shown by a silver mirror (a silver metal) forming which only occurs when an aldehyde is present
There is no reaction with a ketone therefore no visible change
What is Fehling’s Solution
It is a blue solution containing copper 2+ ions in an alkaline solution (NaOH)
How can Fehling’s solution be used to test for aldehydes / ketones
A reaction is shown by the blue solution forming a brick red precipitate if an aldehyde is present
There is no reaction with ketones therefore no visible changes
