Organic compounds

1. Introduction to Organic Chemistry

• Organic chemistry is the study of carbon-containing compounds.
• Organic molecules contain carbon atoms bonded to other elements (H, O, N, halogens, etc.).
• Exceptions: $CO₂, CO,$ carbonates $(CO₃²⁻),$ and cyanides $(CN⁻)$ are inorganic compounds.

2. Chemical Bonding in Organic Compounds

• Carbon forms exactly four bonds.
• Oxygen forms two bonds.
• Hydrogen forms one bond.
• Halogens $(F, Cl, Br, I)$ form one bond.

3. Homologous Series

Definitions

• Homologous series: A group of organic compounds with the same general formula and functional group, differing by a $CH₂$ unit.
• Saturated compounds: Only single bonds between carbon atoms.
• Unsaturated compounds: Have double or triple bonds between carbon atoms.
• Functional group: A specific atom or bond that determines the properties and reactivity of an organic compound.

Classification of Organic Molecules

Homologous Series	General Formula	Functional Group	Suffix	Example
Alkanes	$CₙH₂ₙ₊₂$	-	$-ane$	Propane $(C₃H₈)$
Alkenes	$CₙH₂ₙ$	$C=C$	$-ene$	Propene $(C₃H₆)$
Alkynes	$CₙH₂ₙ₋₂$	$C≡C$	$-yne$	Propyne $(C₃H₄)$
Haloalkanes	$CₙH₂ₙ₊₁X$ $(X = F, Cl, Br, I)$	$-X (halogen)$	$-ane$	2-bromopropane $(C₃H₇Br)$
Alcohols	$CₙH₂ₙ₊₁OH$	$-OH$	$-ol$	Propan-2-ol $(C₃H₇OH)$
Aldehydes	$CₙH₂ₙO$	$-CHO$	$-al$	Propanal $(C₃H₆O)$
Ketones	$CₙH₂ₙO$	$C=O$ (within chain)	$-one$	Propanone $(C₃H₆O)$
Carboxylic Acids	$CₙH₂ₙO₂$	$-COOH$	$-oic$ $acid$	Propanoic acid $(C₃H₆O₂)$
Esters	$CₙH₂ₙO₂$	$-COO-$	$-oate$	Ethyl methanoate $(C₃H₆O₂)$

4. Isomers

Isomers: Compounds with the same molecular formula but different structural arrangements.

Types of Structural Isomers

1. Chain Isomers: Differ in carbon chain arrangement.

• E.g. $Butane$ vs. $2-methylpropane.$

2. Positional Isomers: Functional group appears in different positions.

• E.g. $Butan-1-ol$ vs. $Butan-2-ol.$

3. Functional Isomers: Same molecular formula but different functional groups.

• E.g. $Aldehydes$ vs. $Ketones$ (Propanal vs. Propanone).

5. IUPAC Naming Rules (Nomenclature)

1. Identify the Functional Group → Determines suffix.
2. Find the Longest Carbon Chain → Determines root name.
3. Number the Chain:

• Start from the end closest to the functional group or substituent.

4. Identify Substituents (Side Chains):

• List them alphabetically with appropriate prefixes (e.g. methyl, ethyl, bromo).
• If more than one, use di-, tri-, tetra- (e.g. 2,3-dimethylbutane).

5. Write the Name:

• Use hyphens between numbers and letters (e.g. 2-methylpentane).
• Use commas between numbers (e.g. 2,3-dimethylpentane).

6. Summary

• Organic chemistry focuses on carbon-based compounds.
• Homologous series have a general formula and functional group.
• Isomers have the same molecular formula but different structures.
• IUPAC naming follows set rules based on chain length, functional groups, and substituents.