Key Concepts

Habari Mwanafunzi! Welcome to the Amazing World of Carbon!

Ever wondered what the gas in your mum's kitchen jiko, the sugar you put in your tea, the plastic basin you use for washing, and even you yourself have in common? The answer is one incredible element: Carbon! Welcome to Organic Chemistry, the fascinating study of carbon compounds. It’s not just about labs and complicated formulas; it’s the chemistry of life and everyday materials. Let's get started on this exciting journey together!

Image Suggestion: A vibrant, colourful collage of everyday Kenyan items. In the center, a large, friendly Carbon atom character. Surrounding it are items like a gas cylinder (labeled LPG), a green stalk of sugarcane, a colourful plastic kiondo bag, a wooden chair, and a plate of ugali and sukuma wiki. The style should be bright, slightly cartoonish, and educational.

Why is Carbon the Star of the Show?

Carbon is special, a true "MIP" (Most Important Player) in the world of elements. It has two superpowers that allow it to form millions of different compounds.

1. Tetravalency: This is a fancy word that simply means carbon has four valence electrons. This allows it to form four strong covalent bonds with other atoms. Think of it as having four hands to connect with others!

      C
     /|\
    | | |
   Bond Bond Bond Bond
  (Can connect to 4 other atoms)

2. Catenation: This is Carbon's ultimate superpower! It is the ability of carbon atoms to link together to form long, stable chains and rings. No other element does this as well as carbon. This is how we get the huge variety of organic molecules, from the simple methane to complex plastics.
Catenation in Action (A simple chain): -C-C-C-C-C-C- (And it can go on and on!)

Meet the Simplest Family: The Hydrocarbons

The simplest organic compounds are called hydrocarbons. The name gives you a big clue: they are made of Hydrogen (Hydro-) and Carbon (-carbon) atoms ONLY. The Liquefied Petroleum Gas (LPG) used for cooking in many Kenyan homes is a mixture of simple hydrocarbons, mainly propane and butane.

Real-World Scenario: Think about the process of separating crude oil at a refinery, like the one in Changamwe, Mombasa. They use a process called fractional distillation. This process separates the long carbon chains from the short ones. The shorter, lighter chains become petrol and LPG gas. The medium chains become kerosene (for lighting) and diesel (for lorries and buses). The very long, heavy chains become bitumen, which is used to make our roads. All of these are just different-sized hydrocarbons!

The "Family Business": Homologous Series

Organic compounds are grouped into "families" called homologous series. Think of them like a human family, for example, the Omondi family. They all share the same family name and have similar characteristics. It's the same in chemistry!

A homologous series is a group of organic compounds that have:

• The same general formula. (e.g., Alkanes are C_nH_2n+2)
• The same functional group. (This determines their "family character" or chemical properties).
• Similar chemical properties.
• A gradual change in physical properties (like boiling point) as the chain gets longer.
• Each member differs from the next by a -CH₂- group.

The three main hydrocarbon families we will start with are:

• Alkanes: They only have carbon-carbon single bonds (C-C). They are "saturated".
• Alkenes: They have at least one carbon-carbon double bond (C=C). They are "unsaturated".
• Alkynes: They have at least one carbon-carbon triple bond (C≡C). They are also "unsaturated".

   Ethane (Alkane)     Ethene (Alkene)     Ethyne (Alkyne)
      H   H               H   H               H-C≡C-H
      |   |                \ /
    H-C - C-H                C=C
      |   |                / \
      H   H               H   H
   (Single Bond)       (Double Bond)       (Triple Bond)

How to Name Them: The IUPAC System

To avoid confusion, chemists worldwide agreed on a naming system called IUPAC (International Union of Pure and Applied Chemistry). Let's learn the basic rules. It's like learning a new language, but much easier!

Step 1: Find the Parent Name (The number of carbons)

The first part of the name tells you how many carbon atoms are in the longest continuous chain.

Number of Carbons | Prefix
------------------|--------
        1         | Meth-
        2         | Eth-
        3         | Prop-
        4         | But-
        5         | Pent-
        6         | Hex-
        7         | Hept-
        8         | Oct-

Step 2: Find the Family Name (The type of bond)

The end of the name tells you which homologous series it belongs to.

• If all bonds are single bonds, it's an Alkane, so it ends in -ane.
• If there's a double bond, it's an Alkene, so it ends in -ene.
• If there's a triple bond, it's an Alkyne, so it ends in -yne.

Let's Practice!

Example: Name the molecule CH₃-CH₂-CH₃

1. Count the carbons: There are 3 carbon atoms. The prefix is Prop-.

2. Check the bonds: All are single bonds. So, it's an Alkane. The suffix is -ane.

3. Combine them: Prop- + -ane = Propane. Easy, right?

What if the bond isn't at the start?

For Alkenes and Alkynes, you must state the position of the double or triple bond. You number the carbon chain from the end that gives the multiple bond the lowest possible number.

Example: Name the molecule CH₃-CH=CH-CH₃

1. Longest chain: 4 carbons. Prefix is But-.

2. Family: There is a double bond. Suffix is -ene.

3. Number the chain:
From the left: 1-2-3-4. The double bond starts on Carbon 2.
From the right: 1-2-3-4. The double bond also starts on Carbon 2.
So the position is 2.

4. Combine them: But- + -2- + -ene = But-2-ene.

Let's Do Some Chemistry Math!

The general formula is your best friend. You can use it to find the molecular formula of any member of a family if you know the number of carbon atoms (n).

• Alkanes: C_nH_2n+2
• Alkenes: C_nH_2n
• Alkynes: C_nH_2n-2

Question: What is the molecular formula for the alkane with 6 carbon atoms?

1. Identify the family: Alkane
2. Write down the general formula: CnH2n+2
3. Identify the value of 'n': n = 6 (since there are 6 carbon atoms)
4. Substitute 'n' into the formula:
   C(6)H(2*6)+2
   C6H(12)+2
   C6H14

Answer: The molecular formula is C6H14. This compound is called Hexane.

You've done an amazing job today! These key concepts are the foundation for everything else in Organic Chemistry. Review them, try naming a few simple molecules, and don't be afraid to make mistakes. That's how we learn! In our next lesson, we will dive deeper into the Alkanes. Keep up the great work!