23: Introduction to Organic Chemistry

Organic Chemistry: The Chemistry of Hydrocarbons and Hydrocarbon Derivatives
Carbon can bond in four different ways. All of these bonds are very strong, especially if the bond is to another carbon.



Definitions:
Hydrocarbon: compound containing only carbon and hydrogen.
Hydrocarbon Derivatives: compounds containing carbon and hydrogen and one or more different elements.
Saturated Hydrocarbon: hydrocarbons that contain only single bonds between the carbon atoms.
Unsaturated Hydrocarbon: hydrocarbons that contain one or more multiple bonds (double or triple bonds) between the carbon atoms.
Cyclic Hydrocarbon: a hydrocarbon in which a chain of carbon atoms has formed a ring.
Acyclic Hydrocarbon: a hydrocarbon that does not contain a ring of carbon atoms.

Alkanes:


These are the molecular and structural formulas for the first six. Following the same pattern, after hexane comes heptane, octane, nonane, and decane.

It is important to remember that carbon atoms form four bonds. Do not give your carbon atom more than four things to carry, because he only has four arms.


Condensed Structural Formula: formulas where the bonds around each carbon atom in the compound are not explicitly written.

Example:
Butane has a chain of four carbons, two of which attach to three hydrogens each, and two of which attach to two hydrogens each.

The condensed structural formula for butane is: CH₃CH₂CH₂CH₃ or CH₃(CH₂)₂CH₃

Think of the CH₃ on each end like the front and back of a train, and the CH₂ in the middle keeps getting added on to as you move to the next molecule in the series, just as you would add extra cars to a train.


Constitutional Isomerism: compounds with the same molecular formula but different structural formulas.



Methane, ethane, and propane all only have one isomer. They only have one structural formula each. Butane has two isomers. Pentane has three.


Remember a straight-chain can bend, but if the bonds on the carbon atoms haven't changed, it's not a new isomer.


Line-Angle Structural Formula (Skeletal Structure):


1. Each intersection, endpoint, and kink is a carbon.
2. The carbon to carbon bonds are shown, as well as the bonds between carbon and anything that's not a hydrogen.
3. Every remaining bond on carbon is assumed to be a hydrogen.
4. When counting the carbons in chain, the very beginning of the chain is where you count the first carbon.