Hydrocarbons are organic compounds composed solely of carbon and hydrogen atoms. They form the basis of many organic molecules and are essential components of fossil fuels.
Classification of Hydrocarbons
Aliphatic Hydrocarbons:
- Saturated: Only single bonds between carbon atoms.
- Alkanes: General formula: CnH2n+2
- Cycloalkanes: Cyclic structures, general formula: CnH2n
- Unsaturated: Contain double or triple bonds.
- Alkenes: One double bond, general formula: CnH2n
- Alkynes: One triple bond, general formula: CnH2n-2
Properties of Hydrocarbons
- Physical Properties:
- Boiling and melting points increase with molecular weight.
- Alkanes are nonpolar and insoluble in water.
- Alkenes and alkynes are slightly polar due to the double or triple bonds.
- Chemical Properties:
- Alkanes undergo combustion and substitution reactions.
- Alkenes and alkynes undergo addition reactions.
- Aromatic hydrocarbons undergo electrophilic aromatic substitution reactions.
Important Reactions
- Combustion: Hydrocarbons react with oxygen to produce carbon dioxide and water.
- Substitution Reactions: Alkanes react with halogens (e.g., Cl2, Br2) in the presence of UV light to form haloalkanes.
- Addition Reactions: Alkenes and alkynes react with reagents like hydrogen (H2), halogens, and hydrogen halides to form saturated compounds.
- Electrophilic Aromatic Substitution: Aromatic hydrocarbons react with electrophiles (e.g., NO2+, SO3H+) to substitute hydrogen atoms with other groups.
Isomerism
- Structural Isomerism: Compounds with the same molecular formula but different structural arrangements.
- Geometric Isomerism: Cis-trans isomers arise due to restricted rotation around a double bond.
- Optical Isomerism: Enantiomers are mirror images of each other that are not superimposable.
Remember:
- Practice naming hydrocarbons using IUPAC nomenclature.
- Understand the different types of isomerism and their implications.
- Be familiar with the key reactions of alkanes, alkenes, alkynes, and aromatic hydrocarbons.
