alcohols Flashcards
2 uses of ethanol
-alcoholic drinks
-a solvent
2 uses of methanol
-petrol addative to improve combustion
-chemical feedstock to make organic compounds
how is ethanol prepared?
hydration
ethene + steam
with H3PO4 catlyst high temp and pressure
compare the 2 industrial preparation of ethanol methods
hydration of ethene:
-pure 100% atom economy
-continuous process
-expensive
-non-renewable (source is catalytic cracking of crude oil)
fermentation of sugars:
-batch process
-less than 100% atom economy
-cheap
-renewable (source= sugar cane)
why do alcohols dissolve in water?
polar OH groups form hydrogen bonds with polar h20 molecules
how does chain length of alcohol effect solubility
-water solubility decreases as the chain length increases
-larger part of alcohol molecule is non-polar hydrocarbon chain
-hydrocarbon chain does not form hydrogen bonds with water
why do alcohols have higher boiling points than alkanes with similar Mr
-hydrogen bonds between alcohol molecules
-hydrogen bonds are stronger than london forces
-more energy is needed to break hydrogen b0nds between alcohol molecules
what are the reagents and conditions for elimination of H20 from an alcohol?
R= conc H3PO4 catalyst
C= heat under reflux
define dehydration
a reaction where a water molecule is removed from a saturated molecule to form an unsaturated molecule
what agent is used to oxidize primary and secondary alcohols?
acidified dichromate
whats the observation in oxidation of alcohols?
orange to green
how can an aldehyde be formed by a primary alcohol?
partial oxidation
why is the primary alcohol heated under distillation.?
so the aldehyde is separated from the oxidising agent to prevent further oxidation to the COOH-
how can a carboxyllic acid be made from a primary alcohol?
complete oxidation
accidified dichromate
heat under reflux
why is reflux useful?
-allows mixtures to be heated at high temps for as long as possible wihtout losing any product
so increases yeild
