Halogenoalkanes
Read our general notes on Risk Assessment
Why are tertiary halogenalkanes more reactive than primary halogenalkanes?
020608
Corrie writes .....
Tertiary halogenoalkanes undergo substitution, e.g. by OH-, via a two-step reaction. The first, rate determing step, is the loss of the halogen as a halide ion, X-. This leaves a tertiary carbonium ion, R3C+.
Tertiary carbonium ions are more stable than primary carbonium ions (I won't go into why here), so the activation energy involved for this step is lower than it would be for a primary carbonium ion from a primary halogenoalkane. The primary halogenoalkane would react so slowly via this route that reaction via a different mechansim, requiring a nucleophilic species to assist in breaking the C-X bond, takes over. This is still a much slower process, so tertiary halogenoalkanes appear much more reactive to substitution reactions than primary ones - providing the halogen involved is the same!
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
Rate this page or react
Share your views on this page, 0 ratings so far
updated: 08 June 2008
