Course Topics
Introduction to Organic Compounds
Organic Compounds: Compounds of carbon and hydrogen (hydrocarbons) and their derivatives.
| Key Historical Facts | Details |
|---|---|
| Vital Force Theory | Rejected by Friedrick Wohler in 1828 |
| First Lab-Prepared Organic Compound | Urea (NH₂)₂CO from ammonium cyanate (NH₄CNO) |
| Inorganic Exceptions | CO, CO₂, carbonates, bicarbonates, carbides, cyanides |
Remember Wohler’s experiment: NH₄CNO → (NH₂)₂CO – this destroyed vital force theory!
Classification of Organic Compounds
The carbon skeleton is the basis of classification:
| Type | Description | Examples |
|---|---|---|
| Open Chain (Acyclic/Aliphatic) | Compounds with open chains of carbon atoms | CH₃-CH₂-CH₂-CH₃ (n-Butane) |
| Closed Chain (Cyclic) | Compounds with carbon atoms forming closed rings | Cyclohexane, Benzene |
| Homocyclic (Carbocyclic) | Cyclic compounds with only carbon atoms in ring | Cyclopropane, Benzene |
| Heterocyclic | Cyclic compounds with at least one non-carbon atom | Pyridine, Furan, Pyrrole |
- Contain at least one benzene ring (C₆ ring with alternating double bonds)
- May contain fused or isolated benzene rings
- Examples: Benzene (isolated), Naphthalene (fused), Anthracene (fused)
Classification: Open chain = Straight, Closed chain = Rings, Homocyclic = Only C, Heterocyclic = Other atoms!
Isomerism
Isomerism: Two or more compounds having same molecular formula but different structures.
| Number of Carbon Atoms | Number of Isomers (Alkanes) |
|---|---|
| 4 | 2 |
| 5 | 3 |
| 6 | 5 |
| 7 | 9 |
| 8 | 18 |
| 9 | 35 |
| 10 | 75 |
Types of Structural Isomerism:
- Chain/Skeletal Isomerism: Different carbon skeletons (e.g., n-butane & isobutane)
- Position Isomerism: Different positions of same functional group (e.g., 1-butanol & 2-butanol)
- Functional Group Isomerism: Different functional groups (e.g., ethanol & dimethyl ether, both C₂H₆O)
- Metamerism: Different alkyl groups on either side of same functional group (e.g., diethyl ether & methyl propyl ether)
- Tautomerism: Rapid interconversion between isomers (e.g., keto-enol tautomerism)
Isomers = Same formula, different structures. Chain = Different skeleton, Position = Same group different position!
Geometric (Cis-Trans) Isomerism
Geometric Isomerism: Compounds with same molecular and structural formula but different spatial arrangement of groups.
Conditions for Geometric Isomerism:
- There must be a double bond between two carbon atoms (restricted rotation)
- Two different groups attached to each carbon of the double bond
C = C
H H
C = C
H CH₃
- Cis isomer: Identical groups on same side of double bond
- Trans isomer: Identical groups on opposite sides of double bond
- Geometric isomers have different physical properties (melting point, boiling point, dipole moment)
Cis = Same side (like sisters), Trans = Opposite sides (like trains passing)!
Homologous Series
A homologous series is a family of organic compounds with:
| Characteristic | Description |
|---|---|
| Same Functional Group | All members have identical functional groups |
| Same General Formula | Members differ by CH₂ units: CₙH₂ₙ₊₂ (alkanes), CₙH₂ₙ (alkenes), etc. |
| Similar Chemical Properties | Undergo similar chemical reactions |
| Gradually Changing Physical Properties | Boiling points increase with molecular weight |
| Different Molecular Formula | Each member differs by CH₂ from the next |
- Alkanes: CₙH₂ₙ₊₂ (methane, ethane, propane…)
- Alkenes: CₙH₂ₙ (ethene, propene, butene…)
- Alkynes: CₙH₂ₙ₋₂ (ethyne, propyne, butyne…)
- Alcohols: CₙH₂ₙ₊₁OH (methanol, ethanol, propanol…)
Homologous series = Family of compounds where each member is CH₂ bigger than the previous one!
Functional Groups & Nomenclature
Functional Group: An atom or group of atoms that determines the chemical properties of organic compounds.
| Family | Functional Group | General Formula | Example |
|---|---|---|---|
| Alkane | None (only C-C, C-H bonds) | CₙH₂ₙ₊₂ | CH₄ (Methane) |
| Alkene | C=C | CₙH₂ₙ | CH₂=CH₂ (Ethene) |
| Alkyne | C≡C | CₙH₂ₙ₋₂ | HC≡CH (Ethyne) |
| Alcohol | -OH | CₙH₂ₙ₊₁OH | CH₃OH (Methanol) |
| Aldehyde | -CHO | CₙH₂ₙO | CH₃CHO (Ethanal) |
| Ketone | C=O | CₙH₂ₙO | CH₃COCH₃ (Propanone) |
| Carboxylic Acid | -COOH | CₙH₂ₙO₂ | CH₃COOH (Ethanoic acid) |
- Select longest continuous carbon chain containing functional group
- Number chain to give functional group/lowest substituent the smallest number
- Name substituents alphabetically with their positions
- Use prefixes di-, tri-, tetra- for identical substituents
- Combine: Position-number + substituent + root + suffix (functional group)
Nomenclature: 1. Find longest chain → 2. Number it → 3. Name substituents → 4. Combine!
IUPAC Nomenclature Examples
| Formula/Structure | IUPAC Name |
|---|---|
| CH₃-CH(CH₃)-CH₂-CH₂-CH₃ | 2-Methylpentane |
| CH₃-CH(CH₃)-CH(CH₃)-CH₂-CH₃ | 2,3-Dimethylpentane |
| CH₃-CH₂-CH(Br)-CH₂-CH(Cl)-CH₂-CH₃ | 3-Bromo-2-chlorohexane |
| CH₃-CH=CH-CH₂-CH₃ | Pent-2-ene (or 2-Pentene) |
| CH₂=CH-CH=CH₂ | Buta-1,3-diene |
| CH≡C-CH₂-CH₂-CH(CH₃)-CH₃ | 5-Methyl-1-hexyne |
- Prefix “cyclo” to corresponding alkane name
- Number substituents to get lowest possible numbers
- If only one substituent, no number needed
- Examples: Cyclopropane, Cyclobutane, Methylcyclohexane, 1,2-Dimethylcyclopentane
For alkenes/alkynes: Number from end nearest to multiple bond. For substituted compounds: Alphabetical order of substituents!
Alcohols and Ethers
Alcohols: Contain -OH group, named as alkanols (replace -e with -ol)
| Type | Structure | Example |
|---|---|---|
| Primary (1°) | -OH on carbon attached to 1 other carbon | CH₃CH₂OH (Ethanol) |
| Secondary (2°) | -OH on carbon attached to 2 other carbons | (CH₃)₂CHOH (2-Propanol) |
| Tertiary (3°) | -OH on carbon attached to 3 other carbons | (CH₃)₃COH (2-Methyl-2-propanol) |
Ethers: Contain C-O-C linkage, named as alkoxyalkanes
| Formula | Common Name | IUPAC Name |
|---|---|---|
| CH₃-O-CH₃ | Dimethyl ether | Methoxy methane |
| CH₃-O-C₂H₅ | Methyl ethyl ether | Methoxy ethane |
| C₆H₅-O-CH₃ | Methyl phenyl ether (Anisole) | Methoxy benzene |
Alcohols: Primary (1 carbon neighbor), Secondary (2 neighbors), Tertiary (3 neighbors). Ethers: Alkoxy alkane naming!
Carbonyl Compounds
Aldehydes: Contain -CHO group, named as alkanals (replace -e with -al)
Ketones: Contain C=O group (not at end), named as alkanones (replace -e with -one)
| Type | Naming Rule | Example | IUPAC Name |
|---|---|---|---|
| Aldehyde | Carbonyl carbon gets number 1 | CH₃CHO | Ethanal (Acetaldehyde) |
| Ketone | Number from end nearest to carbonyl | CH₃COCH₃ | Propanone (Acetone) |
| Carboxylic Acid | Replace -e with -oic acid | CH₃COOH | Ethanoic acid (Acetic acid) |
| Formula | Common Name | IUPAC Name |
|---|---|---|
| HCOOH | Formic acid | Methanoic acid |
| CH₃COOH | Acetic acid | Ethanoic acid |
| CH₃CH₂COOH | Propionic acid | Propanoic acid |
| C₆H₅COOH | Benzoic acid | Benzenecarboxylic acid |
Aldehydes = -al (terminal C=O), Ketones = -one (internal C=O), Acids = -oic acid (COOH)!
Applications & Importance
Practical Applications of Organic Chemistry:
- Pharmaceuticals: Most medicines are organic compounds (aspirin, penicillin, paracetamol)
- Polymers & Plastics: Polyethylene, PVC, nylon, polyester for packaging, textiles, construction
- Fuels: Gasoline, diesel, natural gas, biofuels
- Food & Agriculture: Carbohydrates, proteins, fats, vitamins, pesticides, fertilizers
- Cosmetics: Perfumes, soaps, shampoos, lotions
- Dyes & Pigments: Synthetic colors for textiles, paints, inks
- Solvents: Ethanol, acetone, chloroform for industrial processes
- Biochemistry: DNA, proteins, enzymes, hormones
From medicines to plastics to fuels – organic chemistry is everywhere in daily life! Carbon’s versatility makes life possible.