Organic Chemistry: Alkanes and Alkenes

Alkanes

• Saturated hydrocarbons with single bonds between carbon atoms
• General formula: CnH2n+2
• Nomenclature:
  • Prefix: number of carbon atoms (meth-, eth-, prop-, etc.)
  • Suffix: -ane
• Physical properties:
  • Boiling points increase with molecular weight
  • Solubility in water decreases with molecular weight
• Chemical properties:
  • Undergo combustion reactions
  • Can undergo substitution reactions with halogens

Alkenes

• Unsaturated hydrocarbons with one or more carbon-carbon double bonds
• General formula: CnH2n
• Nomenclature:
  • Prefix: number of carbon atoms (eth-, prop-, etc.)
  • Suffix: -ene
• Physical properties:
  • Boiling points lower than alkanes with similar molecular weight
  • Solubility in water decreases with molecular weight
• Chemical properties:
  • Undergo addition reactions (electrophilic addition)
  • Can undergo polymerization reactions

Alkynes

• Unsaturated hydrocarbons with one or more carbon-carbon triple bonds
• General formula: CnH2n-2
• Nomenclature:
  • Prefix: number of carbon atoms (eth-, prop-, etc.)
  • Suffix: -yne
• Physical properties:
  • Boiling points lower than alkenes with similar molecular weight
  • Solubility in water decreases with molecular weight
• Chemical properties:
  • Undergo addition reactions (electrophilic addition)
  • Can undergo polymerization reactions

Stereochemistry

• Study of the three-dimensional arrangement of atoms in molecules
• Types of isomerism:
  • Structural isomerism: different bond connectivity
  • Stereoisomerism: same bond connectivity, different 3D arrangement
• Stereoisomers:
  • Enantiomers: non-superimposable mirror images
  • Diastereomers: non-superimposable, non-mirror images
• Chirality:
  • Molecules with a non-superimposable mirror image are chiral
  • Chiral molecules can rotate plane-polarized light

Aromatic Compounds

• Hydrocarbons with planar, ring-shaped molecules
• General formula: CnHn
• Nomenclature:
  • Prefix: number of carbon atoms (benz-, tolu-, etc.)
  • Suffix: -ene (not always present)
• Physical properties:
  • High melting and boiling points
  • Low solubility in water
• Chemical properties:
  • Undergo electrophilic substitution reactions
  • Can undergo nucleophilic substitution reactions

Alkanes

• General formula: CnH2n+2
• Nomenclature: prefix indicates number of carbon atoms, suffix is -ane
• Physical properties:
  • Boiling points increase with molecular weight
  • Solubility in water decreases with molecular weight
• Chemical properties:
  • Undergo combustion reactions
  • Can undergo substitution reactions with halogens

Alkenes

• General formula: CnH2n
• Nomenclature: prefix indicates number of carbon atoms, suffix is -ene
• Physical properties:
  • Boiling points lower than alkanes with similar molecular weight
  • Solubility in water decreases with molecular weight
• Chemical properties:
  • Undergo addition reactions (electrophilic addition)
  • Can undergo polymerization reactions

Alkynes

• General formula: CnH2n-2
• Nomenclature: prefix indicates number of carbon atoms, suffix is -yne
• Physical properties:
  • Boiling points lower than alkenes with similar molecular weight
  • Solubility in water decreases with molecular weight
• Chemical properties:
  • Undergo addition reactions (electrophilic addition)
  • Can undergo polymerization reactions

Stereochemistry

• Study of the three-dimensional arrangement of atoms in molecules
• Isomerism types:
  • Structural isomerism: different bond connectivity
  • Stereoisomerism: same bond connectivity, different 3D arrangement
• Stereoisomers:
  • Enantiomers: non-superimposable mirror images
  • Diastereomers: non-superimposable, non-mirror images
• Chirality:
  • Molecules with a non-superimposable mirror image are chiral
  • Chiral molecules can rotate plane-polarized light

Aromatic Compounds

• General formula: CnHn
• Nomenclature: prefix indicates number of carbon atoms, suffix is -ene (not always present)
• Physical properties:
  • High melting and boiling points
  • Low solubility in water
• Chemical properties:
  • Undergo electrophilic substitution reactions
  • Can undergo nucleophilic substitution reactions

Learn about the properties and characteristics of alkanes and alkenes, including their general formula, nomenclature, physical and chemical properties, and reactions.