5.3.1 - alcohols Flashcards
what type of molecules are alcohols
organic molecules
what functional group do alcohols contain
-OH functional group
how do you know if somethings an alcohol from its name
it will end in ‘-ol’
eg. methanOL, ethanOL
first few alcohols:
methanol
ethanol
propanol
butanol
in bonding in alcohols where is the -O-H normally attached
at the end (coming off a carbon)
what do you do when the -O-H is attached to the middle of the carbon chain (rather than the end)
add a number, to show which carbon it’s attached to
eg. propan-2-ol, propan-1-ol
what are the three main categories of formula used to represent alcohol
molecular formula
displayed formula
structural formula
what is molecular formula
each element written out once only
the simplest form
eg. C2H6O
what is displayed formula
every atom and every bond drawn out
what is the structural formula
written formula
shows all the elements and the order they come, but without the bonds
eg. CH3CH2OH
what are the two methods of making ethanol
- hydration of ethene
- fermentation of glucose
what conditions are needed for the hydration of ethene
in this method, ethene gas is mixed with steam under the following conditions:
- 300 degrees celsius
- 65 atm pressure
- phosphoric acid catalyst
what raw materials are used in the hydration of ethene
crude oil provides the ethene
what are the advantages of hydration of ethene
- makes pure ethanol
- can run continuously
what are the disadvantages of hydration of ethene
- conditions require lots of energy
- non-renewable raw material used
what conditions are needed for the fermentation of glucose
in this method, glucose is fermented microbiologically under the following conditions:
- yeast (provides enzymes)
- 30 degrees celsius (enzymes optimum temp)
- anaerobic (prevents oxidation)
what raw material is used in the fermentation of glucose
sugar cane provides the glucose
advantages of fermentation of glucose
- renewable raw material used
- conditions not energy-intensive
disadvantages of fermentation of glucose
- makes impure ethanol
- must be done in individual batches
what three ways can ethanol be oxidised
combustion
microbial oxidation
chemical oxidation
combustion (ethanol oxidation):
ethanol tends to combust completely because of the oxygen atom in the -OH group
this results in a non-luminous, BLUE flame
microbial oxidation (ethanol 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
we can represent the microbial use of oxygen in an equation using the ‘[O]’ symbol:
eg. C2H5OH + 2[O] -> CH3COOH + H2O
chemical oxidation (for ethanol oxidation):
to deliberately oxidise ethanol in the lab, heat it with a mixture of:
- potassium dichromate (VI)
- dilute sulphuric acid
this forms ethanoic acid and we use the ‘[O]’ symbol to write an equation for the reaction
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:
ORANGE -> GREEN
