iGCSE Organic Chemistry Review

functional group

A group of atoms that determine a coumpound’s chemical properties.

Homologous series

Molecules in a homologous series contain the same functional group, so they react in similar ways.

Alkene functional group

C=C double bond

Alchohols functional group

-OH

Carboxylic acids functional group

-COOH

Esters functional group

-COO

Isomers

Two molecules are isomers of one another if they have the same molecular formula but different structural/displayed formulae.

Conditions for cracking hydrocarbons

Powdered catalyst (silica or alumina), 600-700 C, vaporized hydrocarbon

Thermal decomposition

Breaking down a molecule into smaller molecules by heating it.

complete combustion equation (for hydrocarbons)

hydrocarbon + oxygen → carbon dioxide + water

incomplete combustion equation (for hydrocarbons)

hydrocarbon + oxygen → carbon monoxide + carbon + water

Substitution reaction requirement

UV light, occuring with alkanes

Addition reaction requirement

Alkene (C=C double bond)

Bromine water if alkene is added

Orange to colorless

Alcohol general formula

C_nH_2n+1OH

What happens to alcohol in complete combustion? + Complete combustion of ethanol

It is oxidized (C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O)

Equation for forming carboxylic acid from alcohol

Alcohol (potassium dichromate in dilute sulfuric acid + heat) → Carboxylic acid

Why is potassium dichromate in dilute sulfuric acid needed for converting an alcohol into an ethanoic acid?

It acts as the oxidizing agent

Microbial oxidation to form carboxylic acids from alcohols

Some microorganisms can use oxygen in the air to oxidize alcohols to produce carboxylic acids.

Two ways to produce ethanol

Fermentation of glucose, reacting ethene with water

Describe the production of ethanol by reacting ethene with water

React ethene with steam in the presence of a phosphoric acid catalyst at a temperature of about 300 ºC and a pressure of about 60–70 atm

Formula for producing ethanol from fermentation

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Conditions required for producing ethanol from fermentation

Yeast, 30 C, anaerobic conditions

Pro and con of producing ethanol using fermentation

Pro: Uses renewable resources unlike ethene which comes from crude oil

Con: Must be distilled to make it concentrated, and purified

Why are anaerobic conditions required for producing ethanol by fermentation?

Oxygen would convert ethanol into ethanoic acid.

acid + metal

salt + hydrogen

acid + metal oxide / acid + metal hydroxide

salt + water

acid + metal carbonate

salt + water + carbon dioxide

What is vinegar?

Aqueous solution of ethanoic acid

How is vinegar (aqeuous ethanoic acid made?)

By oxidizing ethanol (ethanol + oxygen → ethanoic acid + water)

Requirement for producing esters

Acid catalyst such as concentrated sulfuric acid

How to tell if an ester has formed?

A sweet/fruity smell is released

Describe the process of producing an ester (ethyl ethanoate) - 6 steps

1. Add a few drops of concentrated sulfuric acid to a boiling tube using a dropping pipette.

2. Add an equal volume of ethanoic acid and ethanol.

3. Place the boiling tube in a beaker of water placed on a tripod.

4. Heat using Bunsen burner until water starts to boil, then turn it off.

5. After 1 minute, remove the tube and allow it to cool.

6. Once it is cool, pour the mixture into a test tube of sodium carbonate and mix, a layer of ester should form on top of the solution.

Addition polymerization

When lots of unsaturated monomer molecules open their C=C double bonds and join together to form polymer chains.

2 reasons disposing polymers are difficult

1. They are inert so they take very long to biodegrade

2. When burned they produce toxic fumes

Color change when alcohol becomes carboxylic acid when potassium dichromate(VI) and sulfuric acid is added

orange to green