Introduction to Organic Chemistry
Explore the unique bonding properties of carbon, learn about functional groups, and discover how organic molecules are named using IUPAC conventions.
Why Carbon is Special
Organic chemistry is the study of carbon-containing compounds. Carbon is uniquely suited to form the backbone of complex molecules because it has four valence electrons, allowing it to form four covalent bonds. This means carbon can bond to other carbon atoms in chains, rings, and branched structures, creating an enormous variety of molecules.
Types of Carbon-Carbon Bonds
Single Bond
C — C
One shared pair of electrons
Found in alkanes
Sigma bond (σ)
Double Bond
C = C
Two shared pairs of electrons
Found in alkenes
1 sigma + 1 pi bond
Triple Bond
C ≡ C
Three shared pairs of electrons
Found in alkynes
1 sigma + 2 pi bonds
Carbon's versatility: Carbon can form single, double, and triple bonds with itself and with other atoms (H, O, N, S, halogens). It can create straight chains, branched chains, and ring structures -- leading to millions of known organic compounds.
Functional Groups
A functional group is a specific arrangement of atoms within an organic molecule that determines its chemical properties and reactivity. Molecules with the same functional group undergo similar reactions, regardless of the size of the carbon chain.
Common Functional Groups
Hydroxyl
Found in: Alcohols (e.g. ethanol)
Suffix: -ol
Carboxyl
Found in: Carboxylic acids (e.g. ethanoic acid)
Suffix: -oic acid
Carbonyl
Found in: Aldehydes (-al) and Ketones (-one)
Amino
Found in: Amines (e.g. methylamine)
Suffix: -amine
Remember: The functional group determines the class of compound. Changing the functional group changes the chemical properties entirely, even if the carbon backbone stays the same.
IUPAC Naming Conventions and Structural Formulas
The IUPAC (International Union of Pure and Applied Chemistry) system provides a standardised method for naming organic compounds. The name is built from three parts: a prefix (indicating substituents), a root (indicating chain length), and a suffix (indicating the functional group).
Root Names by Chain Length
1C
Meth-
2C
Eth-
3C
Prop-
4C
But-
5C
Pent-
6C
Hex-
7C
Hept-
8C
Oct-
Molecular Formula
C2H6O
Shows types and numbers of atoms only
Structural Formula
CH3CH2OH
Shows how atoms are connected
IUPAC Name
Ethanol
Eth- (2C) + -an- (single bond) + -ol (alcohol)
Naming Steps
1. Find the longest continuous carbon chain -- this gives the root name.
2. Identify the functional group -- this gives the suffix.
3. Number the chain so the functional group gets the lowest possible number.
4. Name and number any substituents (branches) -- these become prefixes.
Key Vocabulary
Organic Compound
A chemical compound containing carbon atoms covalently bonded to other elements, most commonly hydrogen, oxygen, and nitrogen.
Functional Group
A specific group of atoms within a molecule that determines its chemical properties and reactivity (e.g. —OH, —COOH).
Homologous Series
A family of organic compounds with the same functional group and general formula, differing by a CH2 unit (e.g. methane, ethane, propane).
Structural Formula
A representation showing the arrangement of atoms and bonds in a molecule, indicating which atoms are connected to which.
Worked Examples
Name the compound with the structural formula CH3CH2CH2OH.
Step 1: Count the carbon chain: 3 carbons → root = "prop-"
Step 2: All single bonds → "-an-"
Step 3: Functional group is —OH (hydroxyl) → suffix = "-ol"
Step 4: The OH is on carbon 1 → propan-1-ol
Answer: The compound is propan-1-ol (an alcohol with 3 carbons).
Why can carbon form such a vast number of compounds?
Reason 1: Carbon has 4 valence electrons, allowing it to form 4 covalent bonds.
Reason 2: Carbon-carbon bonds are strong and stable, enabling long chains and ring structures.
Reason 3: Carbon can form single, double, and triple bonds, and can bond with many other elements (H, O, N, S, halogens), creating enormous structural diversity.
Write the structural formula for butanoic acid.
Step 1: "But-" = 4 carbon chain
Step 2: "-an-" = all single C-C bonds
Step 3: "-oic acid" = carboxyl group (—COOH) at the end
Answer: CH3CH2CH2COOH
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
How many covalent bonds can a single carbon atom form?
Question 2
Which functional group is present in alcohols?
Question 3
What is the root name for a compound with a 5-carbon chain?
Question 4
Which of these is a correct IUPAC name?
Question 5
A carbon-carbon double bond is found in which homologous series?
Key Concepts Summary
- ●Carbon forms 4 covalent bonds, enabling single, double, and triple bonds in chains, branches, and rings.
- ●Functional groups determine the chemical properties of organic molecules (e.g. —OH for alcohols, —COOH for carboxylic acids).
- ●IUPAC naming uses root (chain length) + suffix (functional group) to give systematic names.
- ●A homologous series is a family of compounds with the same functional group, differing by CH2.
- ●Structural formulas show how atoms are connected, while molecular formulas only show the types and numbers of atoms.