Organic compounds

Organic compounds are divided into two main groups: hydrocarbons, which comprise compounds that contain only carbon and hydrogen atoms, and a second type defined by a functional group that has replaced one of the hydrogen atoms in the molecule. Functional groups can be a single atom (like F, Cl, Br, or I) or a combination of atoms (NH2, OH, C=O, or SH).
Hydrocarbons can be further classified as:

• Alkanes: saturated hydrocarbons that contain a linear or branched chain of only C-C and C-H bonds
• Alkenes: unsaturated hydrocarbons that contain double-bonded carbon atoms (C=C)
• Alkynes: unsaturated hydrocarbons with triply-bonded carbon atoms (–C≡C–) or their cyclic counterparts (carbon atoms that bond to form a ring structure)
• Arenes: aromatic hydrocarbons that contain at least one benzene ring (a ring of six doubly bonded carbon atoms that exhibits unique chemical properties)

Functional groups influence the chemical reactivity of organic molecules. Common functional groups include:

• Oxygen-containing groups (alcohols, ethers, aldehydes, ketones, carboxylic acids, and carboxylic acid esters)
• Nitrogen-containing groups (amines, anilines, and amides)
• Sulfur-containing groups (thiols, thioethers, thioesters, and disulfides)

Carbon atoms can also bond with heteroatoms or other elements to form aliphatic or aromatic heterocyclic rings of varying sizes and reactivities.

Compounds or allotropes of carbon that contain only carbon atoms are classified as inorganic compounds and exhibit novel properties. This class of chemicals has a wide range of applications and includes graphite, diamond, and the more recently discovered graphene, fullerenes, and other carbon nanotubes.