High School Organic Chemistry
IN THIS LESSON
Learn about some more special cases involving organic molecules.
1/4/25: I consider this lesson complete right now, but I am willing to edit it as needed.
Cracking is the breakdown of large alkanes to form smaller alkanes and alkenes. This is done in the oil industry because smaller alkanes are more volatile and easily ignitable, making them more useful for fuel. This process is carried out by either thermal cracking (high heat and pressure) or catalytic cracking (low heat and pressure but with a catalyst).
Some examples of addition reactions are hydration, hydrogenation, hydrogen halide, and halogen reactions. These all break the π bonds in double bonds and form bonds with the carbons instead, turning alkenes into alkanes. Hydration is when a hydrogen atom and an oxygen-hydrogen group from water join to the carbons around a double bond. Hydrogenation is when two hydrogen atoms join to the carbons around double bonds. Hydrogen halide reactions are when one hydrogen atom and one halogen are added to the carbons around a double bond. Halogen reactions are when two halogens are added to the carbons around a double bond.
Elimination reactions are when a combination of atoms is removed from two adjacent carbons so that they will form an additional bond with each other, creating a double bond. This process turns alkanes into alkenes. Some examples of elimination reactions are dehydrogenation and dehydration. Dehydrogenation is when two hydrogen atoms are removed from two adjacent carbons, adding a π bond to an existing bond and making it a double bond. Dehydration is when a hydrogen atom and an oxygen-hydrogen group are removed from adjacent carbons on a molecule, forming a double bond between the carbons and a separate water molecule.
Substitution reactions are when an atom or a group of atoms in a molecule are replaced by a different atom or group of atoms. Halogenation is the replacement of hydrogen atoms by halogens, often creating halogenohydrocarbons. Reacting halogenohydrocarbons with a basic solution will replace the halogens with oxygen-hydrogen groups, creating alcohol groups instead.
Condensation reactions are when a hydrogen atom is removed from one molecule and an oxygen-hydrogen group is removed from another, making the two molecules join together while forming a separate water molecule.
We have covered oxidation-reduction or redox reactions before. For this unit, we can view them as the loss of a hydrogen atom or the gain of an oxygen atom.