Organic Chemistry Notes
1. Isomerism
Isomers
- Compounds having the same molecular formula and same molecular mass, but different arrangements/structures. $$ \boxed{ \text{ Compounds having same moleculer formula but with diff structural formula. } } $$
Types of Isomerism
- Structural isomerism
- Positional isomerism
- Functional isomerism
Structural Isomerism
Example: - Molecular formula: C₄H₁₀ - Different carbon arrangements are possible.
Positional Isomerism
Example:
- Molecular formula: C₃H₈O
- CH₃–CH₂–CH₂–OH → propanol-1
- CH₃–CH(OH)–CH₃ → propanol-2
Functional Isomerism
Example:
- CH₃CH₂OH → ethanol / ethyl alcohol
- CH₃–O–CH₃ → ether
2. Stereoisomers
Stereoisomers are divided into:
- Geometrical isomers
- Optical isomers
Geometrical Isomerism
- Occurs in alkenes.
- Two forms:
- cis
- trans
Examples: - cis-but-2-ene - trans-but-2-ene
Optical Isomerism
- Lactic acid is given as an example of a chiral compound.
3. Valency and Carbon Chains
- Valency of carbon = 4
Examples: - CH₄ - C₂H₆ - C₃H₈ - C₄H₁₀ - C₅H₁₂ - C₆H₁₄ - C₇H₁₆ - C₈H₁₈
Types of Carbon Chains
- Straight chains (alkanes)
- Branched chains
4. Nomenclature of Organic Compounds
- Chemical/systematic names are preferred over common names.
- School name → systematic name
- IUPAC = International Union of Pure and Applied Chemistry.
Alkane General Formula
The first compound in the alkane series is:
Methane (CH₄)
5. Cyclic Compounds
Examples:
- Cyclopropane → 3-membered carbon ring
- Cyclopentane → 5-membered carbon ring
- Cyclohexane → 6-membered carbon ring
6. Carbocyclic Compounds
Carbocyclic compounds include:
(a) Aliphatic
- Open-chain compounds.
(b) Aromatic
Examples:
- Benzene (C₆H₆)
- Naphthalene
- Anthracene
7. Heterocyclic Compounds
If an atom such as oxygen, nitrogen, phosphorus, or sulphur is present in the ring, it is classified as a heterocyclic compound.
Examples:
- Pyridine
- Pyrrole
- Furan
- Thiophene
8. Classification of Organic Compounds
Organic compounds are classified based on:
- Carbon skeleton
- Functional group
- Homologous series
Based on Carbon Skeleton
- Open-chain / aliphatic
- Cyclic
- Carbocyclic
- Heterocyclic
- Aliphatic
- Aromatic
9. Functional Groups
| Functional Group | Representation | Name |
|---|---|---|
| Halide | –X |
Halide |
| Hydroxyl | –OH |
Hydroxyl |
| Aldehyde | –CHO |
Aldehyde |
| Carbonyl | >C=O |
Carbonyl |
| Carboxyl | –COOH |
Carboxylic acid |
| Amide | –CONH₂ |
Amide |
| Ester | –COOR |
Ester |
| Acid chloride | –COCl |
Acid chloride |
Bond Types
C–C→ single bondC=C→ double bondC≡C→ triple bond
Halides
R–X
where X may be:
- F
- Cl
- Br
- I
10. Importance of Organic Compounds
Food
Examples:
- Grains
- Rice
- Fruits
- Oil
- Milk
Clothes
Examples:
- Cotton
- Wool
- Silk
- Nylon
Fuel
Examples:
- Coal
- Petroleum products
Medicine
Examples:
- Penicillin
- Insulin
11. Organic vs Inorganic Compounds
| Organic Compounds | Inorganic Compounds |
|---|---|
| Mainly carbon-containing compounds | Compounds of metals/non-metals and their elements |
| Mostly contain C and H, and may also contain O, N, P, S etc. | Notes mention salts, metals and other compounds |
| Generally insoluble in water but soluble in organic solvents | Different solubility/physical behavior |
| Usually have odour | Many are odourless |
| Generally combustible | Mostly non-combustible |
12. Electronic Orbitals
- s → 1 orbital
- p → 3 orbitals
- d → 5 orbitals
- f → 7 orbitals
Also mentioned:
- Aufbau principle
13. Hydrocarbons
Hydrocarbons are compounds made mainly from:
- Carbon (C)
- Hydrogen (H)
Main Classes
- Alkanes → single bonds
- Alkenes → double bonds
- Alkynes → triple bonds
14. Alkane Homologous Series
| No. of Carbons | Prefix | Name | Formula |
|---|---|---|---|
| 1 | Meth- | Methane | CH₄ |
| 2 | Eth- | Ethane | C₂H₆ |
| 3 | Prop- | Propane | C₃H₈ |
| 4 | But- | Butane | C₄H₁₀ |
| 5 | Pent- | Pentane | C₅H₁₂ |
| 6 | Hex- | Hexane | C₆H₁₄ |
| 7 | Hept- | Heptane | C₇H₁₆ |
| 8 | Oct- | Octane | C₈H₁₈ |
| 9 | Non- | Nonane | C₉H₂₀ |
| 10 | Dec- | Decane | C₁₀H₂₂ |
General Formula
15. Naming Branched Alkanes
Basic Steps
- Find the longest carbon chain.
- Number the chain.
- Give substituents the appropriate numbers.
- Name the substituents.
- Combine the locants + substituent name + parent-chain name.
Examples from the Notes
- 4-methylhexane
- 3-methylhexane
- 2,3-dimethylbutane
- 3,4-dimethylheptane
- 3,4,5-trimethylheptane
- 3,4,5-trimethylhexane
16. Alkyl Groups
An alkyl group is formed by removing one hydrogen from an alkane.
| Alkane | Alkyl Group |
|---|---|
| Methane | Methyl → CH₃– |
| Ethane | Ethyl → C₂H₅– |
| Propane | Propyl → C₃H₇– |
| Pentane | Pentyl |
| Hexane | Hexyl |
General Idea
Alkane − H → Alkyl group
17. Homework: Isomers of C₄H₁₀O
The notebook asks for possible structural isomers of C₄H₁₀O.
Four alcohol structures listed:
1. Butan-1-ol
CH₃–CH₂–CH₂–CH₂–OH
- Butan-2-ol
CH₃–CH₂–CH(OH)–CH₃
- 2-Methylpropan-1-ol
(CH₃)₂CH–CH₂–OH
- 2-Methylpropan-2-ol
(CH₃)₃C–OH
The notebook labels these as 4 total alcohol isomers.
- Carbonyl Group
Aldehyde
Functional group:
–CHO
Ketone
Functional group:
C=O
with carbon groups attached on both sides.
Carboxylic Acid
Functional group:
–COOH
Amide
Functional group:
–CONH₂
Ester
Functional group:
–COOR
Acid Chloride
Functional group:
–COCl
- Homologous Series
Series General Formula Example
Alkane CₙH₂ₙ₊₂ CH₄, C₂H₆ Alkene CₙH₂ₙ C₄H₈ Alkyne CₙH₂ₙ₋₂ C₄H₆ Alcohol CₙH₂ₙ₊₂O Alcohols
Quick Revision Sheet
\(\text{Carbon valency} = 4\) \(\text{Alkane} \rightarrow \text{single bond}\)
\(\text{Alkene} \rightarrow \text{double bond}\)
\(\text{Alkyne} \rightarrow \text{triple bond}\)
\(\text{Alkane formula} \rightarrow CₙH₂ₙ₊₂\)
\(\text{Alkene formula} → CₙH₂ₙ\)
\(\text{Alkyne formula} → CₙH₂ₙ₋₂\)
–OH → Hydroxyl
–CHO → Aldehyde
C=O → Carbonyl
–COOH → Carboxylic acid
–CONH₂ → Amide
–COOR → Ester
–COCl → Acid chloride
–X → Halide
s orbital count = 1
p orbital count = 3
d orbital count = 5
f orbital count = 7
IUPAC = International Union of Pure and Applied Chemistry