Carbonyl Groups

AQA A Level Chemistry A2 Organic

oxidation

loss of electrons and hydrogen

reduction

gain of electrons and hydrogen

reaction between alkenes and hydrogen and nickel

reduction to alkanes

Tollen’s reagant

contains [Ag(NH3)2]+, mild oxidising agent

NaBH4

sodium tetrahydridoborate (III)

uses of NaBH4

reducing agent that contains hydride ions so used for aldehydes and ketones

properties of carbonyl compounds

solubility decreases as chain length increases, dipole-dipole forces create high boiling points, reactive due to large difference in electronegativity between C and O

uses of esters

flavourings, fragrances, solvents, plasticisers

plasticiser

an additive mixed into a polymer to increase its flexibility

biodiesel

liquid fuel made from plant material and recycled elements of the food chain

saponification

alkaline hydrolysis of triglycerol esters which produces salts

esterification

a condensation reaction between an alcohol and a carboxylic acid in the presence of a strong concentrated acid catalyst

ester hydrolysis with dilute acid

the ester is hydrolysed to form the carboxylic acid and alcohol or salts of the carboxylic acid by heating under a reflux and an equilibrium mixture is established as the reaction is reversible

ester hydrolysis with dilute alkali

an irreversible reaction that occurs by heating under reflux in which the ester is fully hydrolysed into the carboxylic acid which then reacts with excess alkali to form a carboxylate salt and alcohol

uses of glycerol

cosmetics, pill capsules in pharmaceuticals, plasticisers, solvents

why acid anyhydrides are better than acyl halides for making esters/amides

reactants and products are less toxic, cheaper, can be used in water but acyl halides can’t (less succeptible to hydrolysis), less rigorous than acyl halides

how to measure melting point of a substance

1. add sample of solid product to a capillary tube and place into heating element of melting point apparatus

2. slowly increase temperature until substance starts to melt

3. record temperature range from when solid just starts to melt to when it fully melts

4. compare melting point to data book values

differences between vegetable oils and animal fats

vegetable oils have unsaturated hydrocarbon chains so can’t pack as closely together so have weaker intermolecular forces whereas animal fats have saturated hydrocarbon chains

how biodiesel is made

oils and methanol are reacted using potassium hydroxide catalyst

reaction of acyl chloride with water

carboxylic acid and HCl gas formed, vigorous reaction

reaction of acyl chloride with ammonia

amide and HCl produced

reaction of acyl chloride with alcohol

ester and HCl are formed

reaction of acyl chloride and primary amine

N-substituted amide and HCl produced

acid anhydride reactions compared to acyl chlorides

less vigorous, carboxylic acid is formed instead of HCl

ingredients to make aspirin

ethanoic anhydride and salicylic acid

why use ethanoic anhydride instead of ethanoyl chloride to make aspirin?

cheaper, doesn’t produce HCl gas, doesn’t react vigorously with water, safer and less corrosive

how to use a separating funnel

1. allow solution to separate into 2 layers and drain off bottom layer or impurities

2. take impure product from funnel and add to a round-bottomed flask

3. add anhydrous calcium chloride to remove aqueous substances remaining

4. invert flask and leave for 20-30 mins

5. filter out solid drying agent via vacuum filtration