High School Organic Chemistry
IN THIS LESSON
Learn some basic facts to know about certain organic molecules.
1/4/25: I consider this lesson complete right now, but I am willing to edit it as needed.
Hydrocarbons are generally non-polar due to only have bonds between carbon and hydrogen and carbon and carbon, with very small differences in electronegativity. They are also generally symmetrical. Functional groups can add polar sections on hydrocarbons if they are polar themselves. Polar functional groups include alcohols (–OH), carboxylic acids (–COOH), amines (–NH₂), ketones (=O), and halogenohydrocarbons (–[halogen]). Other functional groups (alkyl branches, alkenes, and alkynes) are also non-polar and don’t really affect the polarity of the hydrocarbons they’re attached to. Polar molecules are hydrophilic and lipophobic (attract water and repel lipids) while non-polar molecules are hydrophobic and lipophilic (repel water and attract lipids).
Alkanes are relatively stable and usually only form combustion reactions. We know from previous units that these reactions produce water and carbon dioxide.
Alkenes and alkynes are less stable since the double and triple bonds are more reactive than the single bonds. The π bonds will often break to form bonds with other atoms and molecules.
There are two main types of reactions that alkenes and alkynes will form: addition reactions and polymerization reactions. Addition reactions are when the π bonds break off and other atoms and molecules get added into the main molecule. These reactions are sometimes named after the thing being added. For example, hydrogenation for the addition of hydrogen atoms, chlorination for the addition of chlorine atoms, or, more generally, halogenation for the addition of halogens. Polymerization reactions are when multiple units of the same basic molecule, or monomers, react together to form a larger unit containing many repeating monomers, or a polymer.
The last case we should know is about esterification. Esters are often formed when a carboxylic acid group on one molecule and an alcohol group on another molecule join together through a condensation reaction. The oxygen-hydrogen group of one molecule and the hydrogen of the other will break off the molecule, allowing the oxygen that is left to bond the two molecules together. This leaves a water molecule formed by the atoms that broke off the molecules, which is why the reaction is called a condensation reaction.