5.4.1 - Alcohols Flashcards
What are alcohols !?
. Alcohols are organic molecules containing an -OH functional group
What does the start of the name of an alcohol tell us !?
How many carbon atoms it has
What does the end of the name of an alcohol tell us !?
The end of the name is -ol to show it’s an alcohol
The names and diagrams of the binding in the first few alcohols:
Monkeys
Eat
Peanut
Butter
What happens when the -OH group is attached to the middle of the carbon chain !?
It’s possible for the -OH group to be attached to the middle of the carbon chain instead of the end. When this can happen, we include a number in the name to indicate where it is attached
What is the molecular formula !?
Just each element, once only.
Doesn’t show the structure of the molecule at all
What is the displayed formula !?
Every atom and every bond, all drawn out
Perfectly shows the structure of the molecule, but it takes a while to draw
What is the structural formula !?
Somewhere between molecular and displayed
A balance between showing the structure of the molecule, but not taking too long to draw
How do we make ethanol !?
Around 300 million tonnes of ethanol are made a year almost all is made by either
- hydration if ethene
- fermentation of glucose
Hydration of ethene method:
In this method ethene (C2H4) gas is mixed with steam (H2O) under the following conditions
- 300•C
- 65 atm pressure
- phosphoric acid (H3PO4) catalyst
Raw material:
- crude oil provides the ethene
Advantages:
- makes pure ethanol
- can run continuously
Disadvantages:
- conditions require a lot of energy
- non-renewable resource used
What conditions are required for the hydration of ethene !?
. 300•C
. 65 atm pressure
. Phosphoric acid (H3PO4) catalyst
What raw material is required for the hydration of ethene !?
. Crude oil, provides the ethene
What are the advantages of the hydration of ethene method !?
. Makes pure ethanol
. Can run continuously
What are the disadvantages of the hydration of ethene method !?
. Conditions require lots of energy
. Non renewable raw material used
fermentation of glucose method:
In this method glucose (C6H12O6) is fermented microbiologically under the following conditions:
- yeast (provides enzymes)
- 30•C, enzyme optimum temperature
- anaerobic: prevents oxidation
Raw material:
- sugar cane provides the glucose
Advantages:
- renewable raw material used
- conditions are not energy-intensive
Disadvantages:
- makes impure ethanol
- must be done in individual batches
What conditions are required for the fermentation of glucose !?
. Yeast (provides enzymes)
. 30•C, enzyme’s optimum temperature
. Anaerobic: prevents oxidation
What raw material is used in the fermentation of glucose !?
. Sugar cane, provides the glucose
What are the advantages of the fermentation of glucose method !?
. Renewable raw material is used
. Conditions are not energy-intensive
What are the disadvantages of the fermentation of glucose method !?
. Makes impure ethanol
. Must be done in individual batches
How can ethanol be oxidised !?
Ethanol can be oxidised in three ways:
- combustion
- microbial oxidation
- chemical oxidation
Ethanol oxidation: COMBUSTION
Ethanol tends to combust completely because of the oxygen atoms in the -OH group
- this results in a non-luminous blue flame
Ethanol oxidation: MICROBIAL OXIDATION
. Many micro-organisms, such as bacteria and fungi, can use the oxygen in the air to oxidise ethanol into ethanoic acid
. This can only happen aerobically (if the microorganism is growing in the presence of air)
( we can represent the microbial use of oxygen in an equation using the ‘[O]’ symbol
Ethanol oxidation: CHEMICAL OXIDATION
. When we want to deliberately oxidise ethanol in the lab, we heat it with a mixture of
- potassium dichromate(VI) (K2Cr2O7)
- dilute sulphuric acid (H2SO4)
As with microbial oxidation, this forms ethanoic acid and we use the symbol ’[O]’
As this occurs, the orange dichromate(VI) ions are turned into green chromium(III) ions. This means the reaction is always accompanied by the same colour change
