Understanding Functional Groups and Chemical Reactions in Organic Chemistry
Characteristics of homologous series and their reactivity patterns form the foundation of organic chemistry. Compounds are classified as saturated when they contain only single carbon-carbon bonds, while unsaturated compounds feature double or triple bonds between carbon atoms. This fundamental distinction greatly influences their chemical behavior and reactions.
The homologous series of alkanes represents the simplest family of saturated hydrocarbons. These compounds demonstrate relatively low reactivity due to their non-polar nature and strong covalent bonds between carbon-carbon and carbon-hydrogen atoms. However, alkanes readily undergo combustion reactions, which are always exothermic processes. During complete combustion in excess oxygen, alkanes produce carbon dioxide and water vapor. In contrast, incomplete combustion occurs with limited oxygen supply, resulting in carbon monoxide, water vapor, and solid carbon soot formation.
Definition: Free-radical substitution is a type of reaction where atoms or groups of atoms are replaced through a mechanism involving radical intermediates, typically initiated by UV light.
One of the most significant reactions of alkanes is free-radical substitution, particularly with halogens like chlorine or bromine. This process occurs through distinct mechanisms: heterolytic fission, where both shared electrons transfer to one atom creating charged ions, and homolytic fission, where electrons split equally between atoms forming free radicals. The reaction proceeds through initiation triggeredbyUVlight and propagation steps, ultimately producing halogenoalkanes and hydrogen halides.
Example: When methane CH4 reacts with chlorine Cl2 under UV light, it forms chloromethane CH3Cl and hydrogen chloride HCl through a free-radical substitution mechanism.