Halogenoalkanes Flashcards
Key term: Halogenoalkane?
A compound in which one or more H atms in an Allan’s has been replaced by HALOGEN atoms and which only has SINGLE bonds.
General formulae of haloalkanes?
CnH(2n+1)X
X is a halogen atom
What can be said about the carbon-halogen bond?
Is polarised
Physics properties of Haloalkanes?
Chloromethane, chloroethane and bromomethane are gases at room temp
Boiling temps higher than aliases due to more electrons therefore London forced
Are halogenoalkanes soluble in water?
No they’re insoluble as they can’t form hydrogen bonds with water.
Are haloalkanes soluble in organic solvents?
Yes
What is a nucleophile?
A species with a lone pair of electrons that is used to form a covalent bond with a S+ atom. (lone pair donor)
What is a substitution reaction?
An atom or group is replaced by another atom or group. Always 2 REACTANTS and 2 PRODUCTS.
What happens when a haloalkane is heated under reflux with an aqueous solution of alkali?
The halogen is replaced by an OH group and an alcohol is produced.
What is the reagent for a nucleophilic substitution reaction?
Potassium/Sodium hydroxide
What are the conditions needed for nucleophilic substitution?
Warmed under reflux in aqueous solution.
What is another name of saying the reaction type of nucleophilic substitution?
Hydrolysis
A halogenoalkane reacts with water containing silver nitrate solution to form…
To form an alcohol and a solution that contains the halide as an anion.
How can the rates of reaction of the halogenoalkanes be compared?
By noting the time taken for the precipitates to appear (with water containing silver nitrate)
Uses of haloalkanes?
Solvents
Refrigerants
Herbicides and pesticides
Test for halogenoalkanes?
Add sample to aqueous sodium hydroxide and warm for several mins. Cool. Dilute nitric acid until the solution is just acidic to litmus.
Add silver nitrate solution.
Results for test for halogenoalkanes?
Chloroalkanes give a white precipitate soluble in dilute ammonia.
Bromo = cream precious insoluble in dilute ammonia but soluble in conc ammonia.
Iodo= pale yellow precip insoluble in dilute and conc ammonia.
Name the type of reaction that:
Alcoholic haloalkanes
Aqueous haloalkanes
Alcoholic=ELIMINATION
Aqueous=substiution
