Organic chemistry is the chemistry of carbon compounds, and it exists as a separate subject because each carbon atom makes four bonds. Four bonds let carbon link to itself in chains, branches and rings, so a handful of elements (carbon, hydrogen, oxygen, nitrogen) assemble into fats, sugars, alcohols, dyes and medicines. A reader who can count to four and spot a functional group can predict most of what these compounds do.
Part of Organic Chemistry
The carbon-compound foundation under every fuel, solvent, soap, dye and plant medicine a rebuilding community makes.
Four Bonds Per Carbon Atom Is The Whole Idea
The Organic Chemistry carrier states the rule in one line: carbon forms four bonds. Hydrogen forms one, oxygen two, nitrogen three. Take methane, CH4: the carbon holds four hydrogens and has no bond left over. Take ethanol: the carbon skeleton is two carbons joined to each other, and the rest of the bonds are filled by hydrogens and one oxygen.
Because a carbon can bond to another carbon and still have bonds free, there is no natural stopping point. A chain can be two carbons long (ethanol) or a dozen or more (fatty acids in soap). The next article, Bonding Rules, sets out how chains, branches, rings and double bonds follow from the count.
Why A Practical Reader Cares
Almost everything a community burns, eats, wears or takes as medicine is made of these molecules. The carrier lists the uses: fuels, medicines, dyes, adhesives and polymers. Three habits are worth building now.
- Think of a molecule as a backbone plus a reactive group. A bare carbon-hydrogen chain, like candle wax, is nearly inert. The behaviour comes from the attached group, covered in Functional Groups.
- Expect the same atoms to be arranged more than one way. See Isomers.
- Identify by property when you cannot analyse. The carrier gives boiling point, solubility, smell, colour, a small test burn and pH as the field tests.
What You Need
- A pencil and paper. Drawing structures (Structural Formulas) is the working tool.
- The carrier’s list of simple indicators: red cabbage juice or turmeric for pH.
- Nothing else for this article; no reagent is handled here.
Worked Example: Counting Bonds In Ethanol
Ethanol is written C2H6O. Check the bond count for each atom.
- Two carbons, each needing four bonds: 2 × 4 = 8 bond-ends.
- Six hydrogens, one bond each: 6 bond-ends.
- One oxygen, two bonds: 2 bond-ends.
- Total bond-ends: 8 + 6 + 2 = 16, which is 8 bonds, since every bond has two ends.
- One bond joins carbon to carbon, one joins carbon to oxygen, one joins oxygen to hydrogen, and five join carbon to hydrogen. The five count 1 + 1 + 1 + 5 = 8. It balances.
If a drawing does not balance, the drawing is wrong.
Common Mistakes
- Treating “organic” as meaning natural or safe. It only means carbon-based. Methanol, chloroform and plant alkaloids are all organic and all poisonous.
- Memorising names before the bond rule. The rule lets you work out structures; the names follow from Naming Conventions.
Safety
Organic does not mean harmless
Many organic liquids are flammable and their vapours collect in low places, and several are toxic through skin or lungs. Work outdoors or with real ventilation, never taste an unknown compound, and keep ignition sources away from solvents. The practical hazards are covered where each compound is used, for example Methanol Hazards.
What’s Next
- Learn next: Bonding Rules — chains, branches, rings and double bonds
- Combine with: Key Reactions — what you can do with these compounds