Boiling Points of Alkanes
Applied Science: BTEC Level 3 National Extended Diploma, topic 4.3.6
Boiling Points of Alkanes
Alkanes come in a huge range of shapes and molecular formulae. The difference in structures means that alkanes have a wide range of melting and boiling points.
%207.1.1.1%20-%20Four%20smallest%20alkanes%20displayed%20formula,w_800.png)
Straight-chain alkanes
- For straight-chain alkanes, the boiling point increases with chain length.
- Longer chained molecules have the opportunity for greater interactions via induced dipole-dipole interactions when they align next to one another.
Branched alkanes
- Branching reduces the boiling point of alkanes.
- This is because branching reduces the extent to which two molecules can align and form induced dipole-dipole interactions.
Reactivity of alkanes
- Alkanes are generally unreactive. This is because:
- High bond enthalpy means large amounts of energy are required to break the bonds.
- Sigma bonding means that there is a lack of bond polarity.
Test yourself on Boiling Points of Alkanes
Which of the following is true of the boiling points of alkanes?
For straight-chain alkanes, how does boiling point change with increasing chain length?
Which of the following is NOT true of alkane boiling points?