Functional groups provide a mechanism to enable molecular transformations like - connecting two molecules, rearranging a group of atoms in a molecule, replacing one group of atoms with the other, or even removing unwanted atoms. In organic chemistry, these changes occur in the form of reactions- addition (connect), rearrangement (rearrange), substitution (replace), and elimination (remove).
CurlyArrows has created a beginner's guide- Introductory Organic Chemistry as a prerequisite to organic chemistry reactions. It comprises 13 carefully crafted, simplified, illustrative, and descriptive chapters.