chemistry 2.2 Flashcards
What are the two chemical processes by which ethanol can be made?
Fermentation of sugars
Hydration of ethene
How is ethanol manufactured by the hydration of ethene ?
- Using steam in the presence of a phosphoric acid catalyst
- carried out at 300 degrees and 60 atm
- reversible so incomplete…95% conversion rate
How is fermentation used to make ethanol?
- Starch or sugar converted into ethanol and CO2
- catalyst in yeast called zymase
- done at 37degrees
- above 37 the enzyme is denatured
What limits the conversion of sugars to ethanol
Toxicity of alcohol as above 14% denatures enzyme
Done in the absence of air as anaerobic
Give some uses of ethanol other than alcohol
- perfume
- methylated spirits
- mixed with petroleum as fuel
- cleaning fluids
How are spirits made from ethanol?
- heated alcohol-water mixture to distill
- alcohol boils off faster than water and is moved to be condensed
- distillate higher alcohol content than liquid
What are methylated spirits used for and how are they made?
- fuel in spirit burners and camping stoves
- removing paint or ink stains
- made by adding methanol to ethanol and dye; makes it toxic and undrinkable
Defined volatility
The ease for a liquid to turn into a gas which increases with a smaller boiling point
Why do alcohols dissolve in water?
Because hydrogen bonds form between the polar OH groups of the alcohol and water molecules
Why does solubility decrease as the chain length increases
A larger part of the alchohol molecule is made up of a non polar hydrocarbon chain
Hydrocarbon chain does not form hbonds with water molecules
How would you classify a primary alcohol
How would you classify a secondary alcohol
How would you classify a tertiary alcohol
- OH group is attached to a carbon atom with no or one alkyl group
- OH group is attached to a carbon with 2 alkly groups
- OH group attached to a carbon bonded to 3 alkyl groups
What is a suitable oxidising agent and how can it be made
- a solution with acidified dichromate ions
- made by mixing potassium dichromate and sulfuric acid
What do primary alcohols oxidise to
gentle heating = aldehyde
stronger heating = carboxylic acid
Define reflux
continual boiling and condensing of a reaction mixture to make sure the flask does not boil dry while the reaction is taking place
What do secondary alchohols oxidise to form
ketones
What colour does acidified dichromate change to when successfully oxidised
orange to green
Define esterification
the reaction of an alchohol with a carboxylic acid to form and ester and water
How would you prepare an ester
- Put 1cm3 of an alchohol and 1cm3 of a carboxylic acid in a boiling tube and add a few drops of H2SO4
- put the boiling tube in water bath of 80 degrees for 5 minutes
- when done put the boiling tube in a cold water bath and the oil that floats on top is the ester
Define dehydration
an elimination reaction where a water molecule is removed from a saturated molecule to make a unsaturated molecule
What are some uses of halogenoalkanes
organic sythesis
used to prepare many useful materials
aerosol cans
Why do halogenoalkanes contain a polar carbon-halogen bond
- because they have different electronegativities
- the carbon atom is less electronegative than the halogen atom so the bonded pair is more attracted to the halogen atom
- this = polar bond
Define hydrolysis
the reaction of water or aqueous hydroxide to break a chemical compound into two new compounds
What do curly arrows respresent
the movement of an electron pair
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