Basic Organic Compounds (Hydrocarbons & Derivatives)
CSCA Basic Organic Compounds (Hydrocarbons & Derivatives) study guide organized around the publicly available CSCA syllabus. Practice Chemistry questions on aicsca.com.
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This study guide is organized around the publicly available CSCA syllabus for international undergraduate applicants.
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Related formulas, concepts, and glossary terms
Chemistry Formula & Concept Reference
- General Formula of Alkenes
- General Formula of Alkanes
- What is the general formula for alkenes?
- Esterification Reaction of Carboxylic Acids and Alcohols
- What is the functional group of alcohols? How is their general formula expressed?
- What is the general formula for alkynes?
- Combustion Reaction of Alcohols
- What is the general formula for benzene and its homologues?
Chemistry Exam Glossary
Tutorial Content
Basic Organic Compounds (Hydrocarbons & Derivatives)
1. Module Introduction
Organic chemistry is the study of carbon compounds. In the CSCA exam, the focus is on the core concept: **"Structure determines Properties."** We must learn to deduce the chemical properties of organic compounds based on their **Functional Groups**.
This module is divided into two parts:
1. **Hydrocarbons**: Contain only C and H (Alkanes, Alkenes, Alkynes, Benzene).
2. **Derivatives**: Contain C, H, O, etc. (Alcohols, Aldehydes, Acids, Esters).
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2. Hydrocarbons
2.1 Aliphatic Hydrocarbons: Alkanes, Alkenes, Alkynes
Properties depend on the type of carbon-carbon bond (Single, Double, Triple).
| Category | Structure | General Formula | Representative | Key Chemical Properties (Exam Focus) |
| :--- | :--- | :--- | :--- | :--- |
| **Alkanes** | $C-C$ (Single)<br>Saturated | $C_nH_{2n+2}$ | Methane ($CH_4$) | **Stable**. No reaction with acid, base, oxidizers.<br>**Substitution**: $CH_4 + Cl_2 \xrightarrow{light} CH_3Cl + HCl$ |
| **Alkenes** | $C=C$ (Double)<br>Unsaturated | $C_nH_{2n}$ | Ethene ($CH_2=CH_2$) | **Reactive**.<br>1. **Addition**: Decolorizes **Bromine Water**.<br>2. **Oxidation**: Decolorizes **Acidic $KMnO_4$**. |
| **Alkynes** | $C\equiv C$ (Triple)<br>Unsaturated | $C_nH_{2n-2}$ | Ethyne ($CH\equiv CH$) | **Reactive**. Similar to Alkenes (Addition, Oxidation). |
2.2 Aromatic Hydrocarbons: Benzene
* **Structure**: Benzene ($C_6H_6$) bonds are unique, **between single and double bonds**.
* **Chemical Properties (Special)**:
1. **Easy Substitution**: Reacts with liquid Bromine ($+ Br_2$) with $FeBr_3$ catalyst.
2. **Hard Addition**: Difficult to undergo addition (requires high temp/pressure).
3. **Does NOT decolorize Bromine Water or $KMnO_4$** (Key difference from Alkenes).
* *Note*: When Benzene is added to bromine water, the bromine water layer fades due to **Extraction (Physical change)**, not reaction.
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3. Hydrocarbon Derivatives
Functional groups determine chemical characteristics. Memorize this table:
3.1 Ethanol (Alcohol)
* **Functional Group**: Hydroxyl ($-OH$)
* **Key Reactions**:
1. **With Na**: $2CH_3CH_2OH + 2Na \rightarrow 2CH_3CH_2ONa + H_2\uparrow$ (Substitution)
2. **Catalytic Oxidation**: $2CH_3CH_2OH + O_2 \xrightarrow{Cu/\Delta} 2CH_3CHO + 2H_2O$ (Forms Aldehyde)
3.2 Acetaldehyde (Aldehyde)
* **Functional Group**: Aldehyde group ($-CHO$)
* **Key Properties**: Strong **Reducing** agent.
* **Silver Mirror Test**: Reacts with Silver Ammonia solution to form Silver ($Ag$).
* **With New $Cu(OH)_2$**: Forms **Brick-red** precipitate ($Cu_2O$) upon heating.
3.3 Acetic Acid (Carboxylic Acid)
* **Functional Group**: Carboxyl ($-COOH$)
* **Key Reactions**:
1. **Acidity**: Stronger than Carbonic Acid ($2CH_3COOH + Na_2CO_3 \rightarrow 2CH_3COONa + H_2O + CO_2\uparrow$).
2. **Esterification**:
$$CH_3COOH + C_2H_5OH \xrightleftharpoons[\Delta]{Conc. H_2SO_4} CH_3COOC_2H_5 + H_2O$$
* *Note*: Concentrated Sulfuric Acid acts as **Catalyst** and **Dehydrating Agent**.
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4. Summary of Organic Reaction Types
1. **Substitution**: Atom in organic molecule is "replaced" by another atom. (e.g., Alkane halogenation, Esterification).
2. **Addition**: Unsaturated bond ($C=C$) breaks to become saturated. (e.g., Ethene + Bromine).
3. **Oxidation**: Adding Oxygen or removing Hydrogen. (e.g., Combustion, Alcohol to Aldehyde).
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5. Typical Examples
**Example 1: Identification**
How to distinguish Ethanol, Acetic Acid, Benzene, and $CCl_4$?
* **Method**: Add **Water**.
1. **Layers Form**: Benzene (Top, density < water), $CCl_4$ (Bottom, density > water).
2. **No Layers (Miscible)**: Ethanol, Acetic Acid.
* Distinguish Ethanol/Acid: Add **Litmus** or **$Na_2CO_3$** (Acid creates bubbles).
**Example 2: Deduction**
Organic substance A ($C_2H_6O$) reacts with $Na$ to produce gas but does not turn litmus red. What is A?
* **Analysis**: Contains $-OH$ (reacts with Na) but neutral (not acid).
* **Conclusion**: **Ethanol** ($CH_3CH_2OH$).