Alcohols Flashcards
what’s general formula for alcohols
CnH2n+1OH
what are the classifications of alcohols
primary
secondary
tertiary
what does the classification of alcohols relate to
the number of carbon atoms directly attached to the carbon atom carrying the OH group
name the 2 methods ethanol can be produced
1) fermentation of glucose
2) direct hydration of ethene
what does fermentation of glucose do
this process converts sugars such as glucose into ethanol and co2 using the enzymes in yeast cells
what 3 conditions are needed for the conversion of glucose into ethanol via fermentation
- yeast provides enzymes which is the catalyst
- 37° so enzymes do not denture
- absence of O2 (anaerobic respiration)
what are the advantages of fermentation of glucose into ethanol
1) low energy input
2) sugar cane is a renewable source
3) ethanol made this way is said to be a biofuel ( derived from plants and animals )
4) it is said to be CARBON NEUTRAL ( the CO2 released when burnt is equal to CO2 taken in photosynthesis)
give definition of carbon neutral
no net emissions of carbon dioxide to atmosphere
is fermentation of glucose actually carbon neutral and why
no
bc addition CO2 will be made during burning fossil fuels for transportation and harvesting sugar cane crops
give disadvantages of fermentation
1) low yield
2) product is impure (further distillation required)
3) slow rate of reaction
4) batch process
5) environmental issues with loss of habitats and deforestation for producing crops
6) the land could be used for food production
what are the 3 conditions for direct hydration of ethene
- steam
- heat
- concentrated H2SO4 catalyst
what are the advantages of direct hydration of ethene
1) high yield and purity
2) continuous process
3) fast rate of reaction
what are the disadvantages of direct hydration of ethene
1) high energy input
2) ethene is obtained from crude oil which is a non renewable source
what mechanism is direct hydration of ethene
electrophillic addition
what reaction to alcohols undergo to form alkenes
alcohols are dehydrated to form alkenes in elimination mechanism
what are the conditions to form alkenes from alcohols in elimination reaction
heat
concentrated sulphuric acid or phosphoric acid
what is the oxidising agent for alcohols
acidified potassium dichromate (VI)
what colour does acidified potassium dichromate (VI) change to when it acts as an oxidising agent
orange to green
what bond is formed when alcohols are oxidised
a carbonyl bond c=o
what are primary alcohols oxidised to and what conditions ?
aldehydes
distillation f
what are aldehydes oxidised to and under what conditions
carboxylic acids
reflux apparatus conditions
what are secondary alcohols oxidised to and under what conditions
ketones
under distillation apparatus
rank aldehydes, alcohol and carboxylic acids by boiling point and why
aldehydes
alcohol
carboxylic acids
least aldehyde) permanent dipole-dipole forces between molecules are
weaker than hydrogen bond
middle alcohol) hydrogen bonds between the molecules
highest carboxylic acids) hydrogen bonds between the molecules and is a
bigger molecule so more van der waals forces between molecules
what are the 2 oxidising agents to differentiate between aldehydes and ketones
tollens reagent (silver mirror )
fehlings solution (brick red ppt)
