Alcohols
-OH
Ethanol
Aldehydes
-CHO
Propanal
Ketones
COR’
Propanone
Carboxylic acid
-COOH
Ethanoic acid
Acid anhydrides
(CO)2O
Ethanoic anhydride
Esters
-COO-
Ethyl methanoate
Ethers
-O-
Methoxyethane
Primary. Alcohol
The carbon that the OH is bonds with 1 carbon
Secondary alcohol
The carbon that the OH is bonded to, bonds with two other carbons
Tertiary alcohol
The carbon that the OH is bonded to bonds with 3 other carbons
Primary alcohols are oxidised to
Aldehydes and then carboxylic acids
Secondary alcohols are oxidised
To keytones only
Tertiary alcohols aren’t
Oxidised
What oxidising agent is used to oxidise alcohols to carbonyl compounds and carboxylic acids
Acidified potassium dichromate(VI)
Primary alcohols form a carboxylic acid when under
Reflux
If you hate ethanol and potassium dichromate solution and sulphuric acid in a flask it produces
Ethanal which is an aldehyde
To just get an aldehyde you need to use
Distillation apparatus because the aldehyde boils at a lower temperature than the alcohol and evaporates
To produce a carboxylic acid the alcohol has to be vigourously
Oxidised so it is mixed with excess oxidising agent and heated under reflux
Heating under reflex means
Increasing the temperature of an organic reaction to boiling point without losing volatile solvents, reactants or products
The vaporise compounds are cooled so that they can condense and drip back into the reaction mixture
To form a ketone from a secondary alcohol you must
Heat under reflux With acidified dichromate
You can make ethene by
Eliminating water from ethanol in a dehydration reaction
Dehydrating alcohols to form alkenes
Ethanol vapour is passed over a hot catalyst of aluminium oxide
Or You could reflex ethanol with excess concentrated sulphuric acid at 170° C the gas is then collected over water
Concentrated sulphuric acid acts as a dehydrating agent in the elimination reaction it does this by
The hydroxyl group will bond to the H+ ions So the alcohol is protonated giving the oxygen atom a positive charge. The positively charged oxygen will pull electrons away from the neighbouring carbon creating an unstable carbocation intermediate this then loses H+ And the alkene is formed
To form an ester you
Heat carboxylic acid with an alcohol in the presence of an acid catalyst (an esterfication reaction)
Examples of acid catalyst
Concentrated sulphuric acid or hydrochloric acid
Carboxylic acid + alcohol ->
Ester + water
Acid anhydride + alcohol ->
Ester + carboxylic acid
Alcohols React with halide ions in a
Substitution reaction
The halide ions Replace the hydroxyl group in the alcohol to form a
Haloalkane
To make a haloalkane you must
Shake the alcohol with hydrochloric acid
Phenols have
Benzene rings with 0H groups attached
Phenols have a formula of
C6H5OH
How to test for phenols
Add neutral iron (III) Chloride solution and shake if you get a purple solution it is a phenol
Phenols dissolve in water to form
Phenoxide ion and a H+ ion
Phenols react with alkalis to produce a
Salt And water
Phenols don’t react with
Carbonate solutions as the carbonate is not a strong enough base to remove the hydrogen ion from the phenol
Phenols react with
Alkalis and carbonates Giving off CO2 gas
Phenols react with acid anhydrides to form
An Ester and a carboxylic acid
Phenols don’t react with
Carboxylic acid to form an ester
When refluxing you have
Around bottom flask with Anti- bumping granules in. A vertical Liebig condenser where water goes in and out. And you heat it using a water bath
The vertical Liebig condenser causes a solution
To continuously boil evaporate and then condense back into the flask giving it time to react
Distillation separates
Substances with different boiling points
For distillation you have
A reaction mixture in a flask with a thermometer in it and a condenser which has water going in and out in a horizontal way. The mixture is heated up and comes out of the condenser as a pure product into a flask
After distillation the product will still contain
Impurities
Volatile liquids can be purified by
Re-distillation
Separation techniques removes
Any water-soluble impurities from the product
To separate products
Remove products that are in soluble in water, then using a separating funnel add water and shake. The organic layer is less dense than the aqueous layer so should float on top and any impurities will have dissolved in the lower aqueous layer. Open the stopper on the funnel and remove the aqueous layer So the product is in the funnel
Remove water from the purified product by
Drying it using anhydrous salt as it is a drying agent, then filter the mixture to remove the solid drying agent
Anhydrous salt works bye
The drying agent binding to any water present to become hydrated
Filtration is used to
Isolate solid organic products
Filtration
Pour the mixture into a Büchner funnel with filter paper. Below the funnel there should be a sealed side arm flask attached to a vacuum line. The solid will collect in the filter paper
A sealed side arm flask attached to a vacuum line helps
Reduce the pressure inside the flask and will force the liquid through the funnel leaving the solid product on the filterpaper
Organic solids can be purified by
Recrystallisation
Recrystallisation is done by
Adding hot solvent to the impure solid until it dissolves, they should give a saturated solution of the impure product. Leave to cool and the crystals of the product will form, the impurities stay in the solution and to remove the crystals use filtration, wash them and then dry them
When recrystallising the solid must be very soluble
In The hot solvent, but nearly Insoluble when the solvent is cold
If your product is too soluble in the cold solvent most of it will stay in the solution even after cooling. when you filter it you’ll
Lose most of the product giving you a low yield
Melting point can be used to determine
Purity
To use a melting point apparatus to determine the melting point of organic solid you
Put a sample into the glass capillaries and place it inside the heating element. Increase the temperature until the sample turns from a solid to liquid. You can then look at the melting point of a substance in the data box and compare it to your measurements
Impurities in samples will lower
The melting point and hence increase the melting range
Thin-layer chromatography separates
Mixtures
Thin-layer chromatography stages
Stationary phase
Mobile phase
Solvent travels up the plate
A chromatogram shows where the chemicals are
In the stationary phase a
Thin layer of silica is fixed to a glass or metal plate. A line and pencil is drawn at the bottom of the plate and small drops of each mixture are placed on the baseline
In the mobile phase The plate is in a beaker with
Solvent below the baseline but touching the plate. The solvent moves up the plate. Then take it out of the solvent and mark the solvent front line
A chromatograms shows the
Positions of the chemicals which allows you to identify what the chemicals are
If chemicals in the mixture are coloured then there will be
Several coloured dots on the same line
Fluorescent dye and iodine vapour are used as
Locating agents to show where the chemicals are
Chromatography can be used to purify substances this is done by using a
Glass column packed with silica, you then pull your mixture into the column and run the solvent they were continually. The different chemicals in the mix to move down the column at different rates so they come out at different times
Rf value =
Distance travelled by spot/distance travelled by solvent
Chemical industries are more sustainable as they use
Renewable resources, they insure all chemicals and processes involved are safe, and they make sure that waste is minimised and products are biodegradable or recyclable