1. Organic Chemistry
By Ryan

2. Introduction to Organic Chemistry
Watch the following FUN VIDEO!

3. What is Organic Chemistry?
- Simply defined, organic chemistry is a branch of chemistry related to the study of organic compounds
- Organic compounds are usually carbon-containing compounds (Note: There may be exceptions to this definition where carbon-containing compounds such as carbonates are not classified as an organic compound)

4. Homologous Series
- Organic compounds can be divided into further subgroups. Each subgroup is known as a homologous series.
- A homologous series is a family of compounds with the same general formula and similar chemical properties.

5. Functional Groups
- Except for alkanes, the compounds in each homologous series contain a group of atoms known as a functional group.
- A functional group is a group of atoms that gives an organic compound its chemical properties and determines what kind of reactions organic compounds can undergo
- Organic compounds in different homologous series have different functional groups

6. Examples of homologous series
Note: n refers to the number of carbon atoms in the organic compound and R refers to a carbon side-chain
Homologous series
General formula
Functional group
Example
Alkanes
CnH2n+2
C-C
Methane
Alkenes
CnH2n
C=C
Ethane
Aldehyde
CnH2n+1CHO
CHO
Methanal
Alcohol
CnH2n+1OH OH
Methanol
Carboxylic acids
CnH2n+1COOH
COOH
Ethanoic acid
Ester
R-COO-R’’
COO
Methyl ethanoate

7. Prefixes
- Prefixes in the names of organic compounds show the number of carbon atoms in the organic compounds.
Number of carbon atoms
Prefix 1
Meth- 6
Hex- 2
Eth- 7
Hept- 3
Prop- 8
Oct- 4
But- 9
Non- 5
Pent- 10
Dec-

8. Examples Alkanes - General Formula CnH2n+2
Aldehydes - General Formula CnH2n+1CHO
Number of carbon atoms
Name/Molecular Formula 1
Methane (CH₄) 2
Ethane (C₂H₆) 3
Propane (C₃H₈) 4
Butane (C₄H₁₀)
Number of carbon atoms
Name/ Molecular Formula 5
Pentanal (C₅H₁₁CHO) 6
Hexanal (C₆H₁₃CHO) 7
Heptanal (C₇H₁₅CHO) 8
Octanal (C₈H₁₇CHO)

9. Structure of organic compounds
- An organic compound is said to be saturated if each carbon atom in the organic compound is bonded to the maximum number of other atoms (Each carbon atom can bond to a maximum of 4 other atoms as they are tetravalent)
- Examples of saturated organic compounds are the alkanes and the cycloalkanes.

10. Properties of Alkanes/Alkenes
- Alkanes are unreactive as they are saturated
- Alkenes are reactive as they are unsaturated (due to the presence of C=C bonds)
- Boiling points and melting points of alkanes/alkenes increase as the number of carbon atoms increases due to an increase in the van der Waal’s forces of attraction (Methane is a gas, but octadecane is a solid)
- Alkanes/Alkenes are insoluble in water but are soluble in organic solvents
- Alkanes/Alkenes are less volatile as the number of carbon atoms increases due to an increase in the van der Waal’s forces of attraction
- Alkane/Alkenes are denser as the number of carbon atoms increases

11. Reaction of alkanes (1) - Combustion
Alkanes/Alkenes burn in excess oxygen to form carbon dioxide and water. Incomplete combustion of alkanes/alkenes forms carbon monoxide and water.
Example
Methane + Oxygen Carbon Dioxide + Water
_ CH₄ + _ O₂ _ CO₂ + _ H₂O

12. Reaction of alkanes (2)
- Substitution reaction (Only occurs for alkanes)
A substitution reaction is a reaction in which an atom or group of atoms replace other atoms in a molecule
Example - Chlorination of alkanes under UV light (free radical substitution)
Methane + Chlorine Chloromethane + Hydrogen Chloride
Chloromethane + Chlorine Dichloromethane + Hydrogen Chloride
Note: Presence of UV light is a necessary condition for chlorination of alkanes

13. Reaction of alkenes (1) - Addition reactions (Alkenes only)
An addition reaction is a reaction in which two or more molecules combine to form a single product.
Example 1 - Hydrogenation of alkenes to produce alkanes with nickel as a catalyst
Example 2 - Bromination of alkenes to produce bromoalkanes
Example 3 - Hydration (reaction with steam) of alkenes to produce alcohols
Conditions needed for Example 3 : 300°C , atm pressure, with phosphoric (V) acid as the catalyst

14. Reaction of alkenes (2) - Polymerisation
Polymerisation is a process whereby many identical alkene molecules join together in an addition reaction to form a big molecule known as a polymer.
Example - Polymerisation of ethene to form poly(ethene)

15. Testing for Unsaturated Compounds
- Aqueous bromine can be used to test for unsaturated compounds
- When unsaturated compounds are added into bromine, the solution changes from reddish-brown in colour to colourless (decolourisation)
- This is because the unsaturated compounds undergo addition reactions with the aqueous bromine and are brominated

16. Isomers
- Isomers are different compounds with the same molecular formulae but different structural formulae and different boiling points.
- There are many types of isomerism: cis-trans isomerism, functional group isomerism, optical isomerism, positional isomerism and chain isomerism
- Example of isomers are the alkenes and cycloalkanes

17. Cracking of petroleum fuel
- Large alkane molecules in petroleum can be broken down into smaller molecules through cracking.
- Two types: Catalytic cracking (passed over catalyst) and steam cracking (mixed with steam)
- When an alkane is cracked, there are many different combination of products that can be formed.
- For example, cracking of decane can produce propene + heptane OR propene + heptene + hydrogen
- Cracking is mainly used to provide fuel for vehicles and produce hydrogen

18. Properties of Alcohols/Carboxylic Acids
- Alcohols/ Carboxylic acids have low boiling points and as the number of carbon atoms in the alcohols increase, the boiling points of the alcohols increase.
- Alcohols are soluble in water. As the number of carbon atoms in the alcohols increase, their solubility in water decreases.
- Carboxylic acids also have chemical properties similar to that of typical acids.

19. Reactions of alcohols - Combustion to produce carbon dioxide and water
- Oxidation to produce a carboxylic acid
Example : Oxidation of ethanol to ethanoic acid with acidified potassium manganate (VII) solution
- Esterification (Reaction with carboxylic acids to form esters)

20. Esters
- An ester is an organic compound formed due to the reaction between an alcohol and a carboxylic acid.
- Carboxylic acid + Alcohol ester + water
- Esters are sweet-smelling, good solvents for organic compounds and have low boiling points
- Esters have the general formula of R-COO-R’’ where R and R’’ are carbon side chains
Note: The sweet smell of fruits such as bananas can be attributed to esters!

21. Nomenclature for Esters
- Esters are named by placing the prefix of the alcohol reactant at the front and the prefix of the carboxylic acid reactant at the back
- Example: Methanol + Ethanoic acid Methyl ethanoate + Water

22. THE END THANK YOU AND HOPE YOU HAD FUN !!!