Organic Compounds

Organic Compounds

Definition and Basics

  • Organic compounds are substances made up mostly of carbon and hydrogen atoms; they may also contain elements like oxygen, sulphur, nitrogen, phosphorus, and halogens.
  • The key feature of organic compounds is the carbon skeleton, which can be chains, branches, or rings of carbon atoms.
  • Organic compounds are categorised into different classes: alkanes, alkenes, alkynes, alcohols, ethers, esters, aldehydes, ketones, carboxylic acids, amides, amines, and aromatic compounds.


  • Alkanes are organic compounds that consist entirely of single-bonded carbon and hydrogen atoms and lack functional groups. Each carbon atom forms 4 bonds (either C-H or C-C bonds).
  • They are saturated hydrocarbons, meaning they contain as many hydrogen atoms as possible.
  • Alkanes are generally unreactive except reaction with oxygen - combustion.

Alkenes and Alkynes

  • Alkenes are hydrocarbons that contain a carbon-carbon double bond. Alkynes, on the other hand, possess a carbon-carbon triple bond.
  • Both alkenes and alkynes are categorised as unsaturated hydrocarbons since they have fewer hydrogen atoms than alkanes.
  • Alkenes and alkynes react through addition reactions where the double or triple bond opens to allow the attachment of other atoms.

Functional Groups

  • The functional group of an organic compound is an atom, or a group of atoms, that has certain chemical properties regardless of the rest of the molecule.
  • The functional group is the center of reactivity in an organic compound.
  • Examples include hydroxyl (-OH) in alcohols, carbonyl (>C=O) in aldehydes and ketones, carboxyl (-COOH) in carboxylic acids, and amino (-NH2) in amines.


  • Isomers are compounds with the same molecular formula but different molecular structures or different spatial arrangements of atoms.
  • Structural isomers have different covalent arrangements of their atoms.
  • Geometric isomers, a type of stereoisomer, have the same bond connections but different spatial arrangements due to the inflexibility of double bonds.

Reactions of Organic Compounds

  • Common types of reactions include substitution, addition, and elimination reactions.
  • Substitution reactions involve replacing one or more atoms in the compound, often by a more reactive atom or group.
  • In addition reactions, atoms are added to a molecule without any other atoms being removed.
  • Elimination reactions involve the removal of atoms from a molecule, often resulting in the formation of a double or triple bond.


  • Spectroscopy (mainly IR and NMR) is a crucial tool in determining the structure and functionality of organic compounds.
  • IR spectroscopy provides information about the presence of functional groups in a molecule.
  • NMR spectroscopy provides information regarding the carbon-hydrogen framework of an organic compound.