Reactivity of Alkanes
- The unreactive nature of alkanes can be explained by two factors
- The high bond enthalpies of the C-C and C-H bonds
- The very low polarity of the sigma (σ) bonds present
Bond enthalpy
- The C-C bond has a bond enthalpy of 346 kJ mol-1 and the C-H bond has a bond enthalpy of 411 kJ mol-1
- The C-H bond is stronger as the bond length is less than the C-C bond
- This is because the hydrogen atom only consists of one shell, so the distance between the nuclei is shorter
- Creating greater force of attraction to the nuclei and the pair of electrons between them
Polarity
- The electronegativities of carbon and hydrogen are very similar, therefore the bonds will have very low polarity
Ethane is an example of an alkane that lacks polarity due to almost similar electronegativities of the carbon and hydrogen atoms