Lesson Notes By Weeks and Term v4 - SHS 2
CHARACTERIS ATION OF ORGANIC COMPOUNDS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
CHARACTERIS ATION OF ORGANIC COMPOUNDS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Chemistry
Class: SHS 2
Term: 2nd Term
Week: 14
Grade code: 2.3.2.LI.2
Strand code: 3
Sub-strand code: 1
Content standard code: 2.3.2.CS.1
Indicator code: 2.3.2.LI.2
Theme: CHEMISTRY OF CARBON COMPOUNDS
Subtheme: CHARACTERIS ATION OF ORGANIC COMPOUNDS
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
This lesson introduces two important families of organic compounds: alkenes and alkynes. Unlike the alkanes we have studied, these compounds are "unsaturated," meaning they have double or triple carbon-carbon bonds. This seemingly small difference makes them much more reactive and incredibly useful. In our daily lives in Ghana, we see their applications everywhere – from the polythene bags ("olonka") and "pure water" sachets we use, to the process of ripening plantain and mangoes, and even in the work of our local welders. By understanding their structure and reactions, we can better appreciate the chemistry that shapes our world.
PART A: ALKENES (The C=C Double Bond Family)
Alkenes are unsaturated hydrocarbons because they contain at least one carbon-carbon double bond (C=C). This double bond is the functional group and is the centre of their chemical reactivity. General Formula and Homologous Series The general molecular formula for alkenes is CₙH₂ₙ (where n ≥ 2).
Homologous Series of the First Six Alkenes: | n | Molecular Formula | IUPAC Name | Condensed Structural Formula | |---|---|---|---| | 2 | C₂H₄ | Ethene | CH₂=CH₂ | | 3 | C₃H₆ | Propene | CH₂=CH-CH₃ | | 4 | C₄H₈ | Butene | CH₂=CH-CH₂-CH₃ | | 5 | C₅H₁₀ | Pentene | CH₂=CH-CH₂-CH₂-CH₃ | | 6 | C₆H₁₂ | Hexene | CH₂=CH-CH₂-CH₂-CH₂-CH₃ | IUPAC Nomenclature for Alkenes The rules are similar to alkanes, but with a focus on the double bond. Rule 1: Find the longest continuous carbon chain that contains the double bond. The parent name ends in -ene. Rule 2: Number the carbon atoms in the chain starting from the end closer to the double bond, giving the first carbon of the C=C bond the lowest possible number. This number is placed before the "-ene" (e.g., but-1-ene, but-2-ene). Rule 3: Name and number any substituent groups (like methyl, ethyl, chloro) as you did for alkanes.