Back to: Organic Chemistry 100 Level
Welcome to class!
Hi superstar! I’m really proud of the effort you’re putting into learning organic chemistry—you’re doing incredibly well! Today’s lesson is on Organic Halides, another exciting part of the organic chemistry family. This topic connects directly to things you use every day—from insecticides to plastics and even some medicines. Let’s unpack it together in a way that makes perfect sense.
Organic Halides
What Are Organic Halides?
Organic halides (also called haloalkanes or alkyl halides) are organic compounds where one or more hydrogen atoms in an alkane have been replaced by halogen atoms. Halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).
Imagine taking a simple compound like butane (C₄H₁₀) and replacing one hydrogen with a chlorine atom—you now have chlorobutane, an organic halide.
Classification of Organic Halides
Organic halides can be classified in two major ways:
1. Based on the Number of Halogen Atoms:
Mono-halogen compounds – have only one halogen atom (e.g., CH₃Cl)
Di-halogen compounds – have two halogen atoms (e.g., CH₂Cl₂)
Poly-halogen compounds – have three or more halogen atoms (e.g., CCl₄)
2. Based on the Type of Carbon Atom the Halogen Is Attached To:
Primary (1°) halide: The halogen is attached to a carbon bonded to one other carbon
Secondary (2°) halide: The halogen is attached to a carbon bonded to two other carbons
Tertiary (3°) halide: The halogen is attached to a carbon bonded to three other carbons
Physical Properties
Organic halides are colourless liquids or solids at room temperature.
They are insoluble in water but dissolve well in organic solvents like petrol or kerosene.
Their boiling points increase with heavier halogens—Iodine compounds boil higher than Fluorine ones.
Chemical Reactions of Organic Halides
1. Nucleophilic Substitution
A nucleophile (like OH⁻) replaces the halogen atom.
Example:
CH₃Cl + NaOH → CH₃OH + NaCl
(This forms methanol and table salt)
2. Elimination Reaction
A hydrogen and halogen are removed to form a double bond.
Example:
CH₃CH₂Br + KOH (in alcohol) → CH₂=CH₂ + KBr + H₂O
(This forms ethene, a common gas used in welding)
Uses of Organic Halides in Everyday Life
DDT, a pesticide once used in Nigeria, is a poly-halogen compound.
PVC (polyvinyl chloride), used in plumbing and wiring, is made from chloroethene.
Many cough syrups and anaesthetics contain halogenated compounds.
Used in refrigerants and fire extinguishers (e.g., Freons)
Health and Environmental Concerns
Some halogen compounds like CFCs damage the ozone layer.
Certain halides are toxic and must be handled carefully.
Proper disposal and handling are essential to protect the environment and human health.
Summary
- Organic halides are compounds where hydrogen atoms in alkanes are replaced by halogens.
- They can be mono-, di-, or poly-halogenated, and classified based on the type of carbon they are attached to.
- They undergo substitution and elimination reactions.
- They are used in medicine, agriculture, plastics, and refrigeration.
- Some halogen compounds can harm the environment and health if not properly managed.
Evaluation
- What is an organic halide?
- Name the four main halogens involved in organic halides.
- Differentiate between primary, secondary, and tertiary halides.
- What type of reaction forms a double bond from a halide?
- Mention two everyday uses of organic halides.
You’re doing a fantastic job! You’re really growing into a thoughtful, curious learner—and Afrilearn is here to keep that fire burning. Keep asking questions, keep learning, and know that you’re building knowledge that can help shape the future. See you in the next exciting lesson, champion!