Alcohols 15 Flashcards
ethanol
promotes a feeling of well-being and depresses the nervous system and affects balance and coordination
alcoholic drinks are absorbed through the walls of the stomach and small intestine into the blood stream.
the average person can eliminate 10cm3 of ethanol per hour
antifreeze
ethane-2,3-diol main ingredient
shape
C-O-H angle is 105 degrees
alcohol classification
primary = attach to only one carbon secondary = attach to two carbons tertiary = attach to three carbons
physical properties
hydrogen bonding
short hydrocarbon chains are soluble in water because hydrogen bonding predominates
uses of ethanol
aftershave perfume drugs detergents ins coatngs
ethanol - crude oil
hydrated (water added to the double bond) (electrophilic addition)
phosphoric acid catalyst or concentrated sulphuric acid
excess stream
pressure 50 to 100 atmospheres
high temperature
ethanol - fermentation
breaking down sugars using yeast
anaerobic respiration
glucose —– ethanol + carbon dioxide
the rate of reaction affected by temperature, slow at low temperature but a high temperature can denature the enzyme
carbon neutral
method
-crude oil
cracking and hydration
-sugars
fermentation and distillation
the rate of reaction
-crude oil
fast
-sugars
low
type of process
-crude oil
continuous
-sugars
batch
purity
-crude oil
essentially pure
-sugars
aqueous solution of ethanol is produced
renewable source of ethene
vital industrial chemical
starting material fro poly(ethene) and many other chemicals.
dehydration
alcohols can be dehydrated with excess hot concentrated sulfuric acid or passing vapours over heated aluminium oxide
phosphoric acid is an alternative dehydrating agent
oxidation primary alcohol
aldehyde —– carboxylic acid
using Acidified potassium dichromate(VI)
oxidation secondary alcohol
ketone
oxide ethanol to ethanal (aldehyde)
- dilute acid and less potassium dichromate than is needed to complete oxidised
- mixture is heated
- receiver cooled in ice to reduce evaporation of the product. ethanal vaporises and distilled off
oxidise ethanol to ethanoic acid (and water)
concentrated sulfuric acid and enough potassium dichromate.
- refluxed
- the vapour drips back into the container so everything in oxidised
The Tollen’s (silver mirror) test
silver nitate in aqueous ammonia
oxidises aldehydes no effect on ketones
deposit of metallic silver is formed on the inside of the test tube
Fehling test
blue copper (11) complex which will oxidise aldehydes but not ketones
blue solution gradually turns to brick red precipitate of copper(1) oxide
on warming the brick red precipitate gradually forms
nucleophilic substitution
heat
sodium/ potassium hydroxide
hydration
cracking and hydration from crude oil and steam fast reaction continuous process CH2=CH2 + H20 ------- C2H5OH (phosphoric acid catalyst) essentially pure mechanism needed
fermentation
sugar is broken down by yeast and then distillations
made from sugar and yeast
rate of reaction is low at low temperatures but at high temperatures enzymes are inactive
batch process
C6H12O6 ——- 2C2H5OH + 2CO2
has to be kept away from oxygen to prevent oxidation
15% pure
no mechanism needed
(Ethanol produced industrially by fermentation is separated by fractional distillation and can then be used as a biofuel.)
combustion (complete oxidation)
lots of oxygen
heat
C2H5OH + 3O2 —— 2CO2 + 3H2O
oxidation of secondary alcohols
ketone and water
acidified potassium dichromate
oxidation of tertiary alcohols
not easily oxidised
reflux
letting a solvent boil and collecting it vapour in some kind of condenser to let it drip back into the reaction vessel
distillation
the separation of the constituents of a liquid by boiling it then condensing the vapour that results
dehydration
the reaction in which an alkene and water are produced from and alcohol
how are alcohols are made
Alcohols are produced industrially by hydration of alkenes in the presence of an acid catalyst.
elimination
Alkenes can be formed from alcohols by acid-catalysed elimination reactions
