2.6 Halogenoalkanes Flashcards
Why are halogenoalkanes susceptible to nucleophilic attack?
As the halogens are more electronegative than carbon they create a polar bond of delta + carbon and delta - halogen. The delta + on the carbon is vulnerable to attack by a nucleophile (+)
What is a nucleophile?
A species with a lone pair of electrons that can be donated to an electron deficient species.
Draw the mechanism of the nucleophilic subsitution of chlloropropane NaOH:
How are alcohols prepared from halogenoalkanes?
Nucleophillic subsittution using NaOH + heated under reflux or Hydrolysis with water
What is the order in rate of hydrolysis of halogenoalknaes?
iodo > bromo > chloro
fastest slowest
What is the test for halogenoalkanes?
The test is called the silver nitrate test. To begin the excess sodium hydroxide must be neutralised using dilute nitric acid (this separates the halogen from the rest) . Then aqueos silver nitrate is added to the halide.
Cl- white p
br- cream p
I- yellow p
How can an elimination reaction occur with a halogenoalkane?
The alkali, such as NaOH, would need to be dissolved in ethanol without any water present.
What happens in an elimination reaction?
Basically an alkali like NaOH would nab the halide and a H ion would be nabbed and match up with the OH from NaOH to make H20, therefor the products usually look something like –> NaBr + H20
This leaves the old halogenoalkane with a double bond.
How are alkenes produced from halogenoalkanes?
Elimination reactions
Why are the use of halogenoalkanes monitored and reduced?
As some are bad for the environment such as CFC’s
CFC’s damage the ozone layers which prevents harmful UV rays reaching the earths surface. This happens as CFC’s as the UV rays cause free radicals of chlorine.
