4.1.2 - Alkanes

• What is a σ-bond?

  A covalent bond formed by head-on overlap
• How do σ-bonds differ from other bonds?

  They can rotate freely
• What is the general formula for alkanes?

  CnH2n+2
• What happens to the boiling points of shorter, more branched alkanes?

  They have higher boiling points
• Why do shorter, more branched alkanes have higher boiling points?

  Weaker London forces require less energy
• What is bond enthalpy?

  Energy required to break one mole of bonds
• How do actual bond enthalpies differ from average bond enthalpies?

  Actual may differ from average due to context
• What is complete combustion?

  Burning in plentiful oxygen supply
• What are the products of complete combustion of alkanes?

  Water and carbon dioxide
• What defines a covalent bond?

  Electrostatic attraction between shared electrons
• What is electron pair repulsion?

  Electrons repel, positioning them far apart
• What shape do carbon atoms in alkanes adopt?

  Tetrahedral shape with bond angle 109.5°
• What is homolytic fission?

  Bond breaks, each atom gets one electron
• What is a hydrocarbon?

  A compound with hydrogen and carbon only
• What occurs during incomplete combustion?

  Burning in limited oxygen produces various products
• What products can result from incomplete combustion of alkanes?

  Water, carbon monoxide, particulates, CO2
• What is initiation in radical substitution?

  First step forming radicals in mechanism
• What are London forces?

  Induced dipole-dipole interactions between molecules
• What is a polar bond?

  A covalent bond with a permanent dipole
• What is propagation in radical substitution?

  Intermediate steps where radicals react
• What is a radical?

  A species with an unpaired electron
• How do alkanes undergo radical substitution?

  With chlorine or bromine in UV light
• What is the outcome of radical substitution reactions?

  Forms a mixture of organic products
• What does saturated mean in organic chemistry?

  Only contains single C-C bonds
• What is termination in radical substitution?

  Final steps where two radicals combine
• What is the shape of a tetrahedral molecule?

  Central atom has 4 bonding pairs