Alcohols Flashcards
what is an alcohol
an organic molecule containing an -OH functional group
molecular and display formula for ethanol
what would you name this molecule
propan-2-ol
structural formula of ethanol
what are the two methods of making ethanol and what is the main reason for choosing one
- hydration of ethene
- fermentation of glucose
which method gets used depends mostly on the availability of crude oil or sugar cane in different parts of the world
what is the raw material used in the hydration of ethene
crude oil (provides the ethene)
advantages of the hydration of ethene method for creating ethanol
- makes pure ethanol (and therefore produces no waste products)
- can run continuously
- fast rate of reaction
disadvantages of the hydration of ethene method for creating ethanol
- conditions require a lot of energy
- non-renewable raw material used
how to perform the hydration of ethene method for creating ethanol
Ethene is made when alkanes undergo cracking, then ethene gas is mixed with steam under the following conditions:
300*C
65 atm pressure
phosphoric acid catalyst
what raw material is used in the fermentation of glucose
sugar cane
disadvantages of the fermentation method for creating ethanol
- makes impure ethanol
- must be done in individual batches
- slow process (20-60hours)
- CO2 gas is released
advantages of the fermentation method for creating ethanol
- renewable raw material used
- conditions do not require a lot of energy
how is the fermentation method for creating ethanol carried out
glucose is fermented microbiologically under the conditions:
- yeast present (provides enzymes)
- 30*C (enzymes optimum temperature)
- anaerobic (prevents oxidation)
during the fermentation of glucose what would happen if there was no bung or air trap
the ethanol will be oxidised and form ethanoic acid
during the fermentation of glucose why do we use an air trap instead of a solid bung
it lets gas out but not in - avoids the co2 building up and causing an explosion
what do you have to do to the product of the fermentation of glucose
fractional distillation - to separate the ethanol and the water.
water has a higher boiling point than ethanol so as they both rise up the column it cools and condenses and fall back down while the ethanol reaches the top of the fractionating column and enters the condenser
what are the three ways that ethanol can be oxidised
- combustion
- microbial oxidation
- chemical oxidation
how does microbial oxidation work
microorganisms such as bacteria and fungi can use the oxygen in the air to oxidise ethanol into ethanoic acid
how does chemical oxidation occur and how can we observe it
When we want to deliberately oxidise ethanol in the lab, we heat it with a mixture of:
* Potassium dichromate
* Dilute sulfuric acid
the reaction is always accompanied by the same colour change because the orange dichromate ions are turned into green chromium ions.
