3.3.4. Haloalkanes Flashcards
What is a halogenoalkane?
A saturated hydrocarbon with a halogen bonded to at least one carbon
What explains halogenoalkanes increased reactivity relative to alkanes?
The polar carbon-halogen bond
Why do halogenoalkanes contain polar bonds?
Due to the difference in electronegativity between carbon and halogens
Which elements are “eliminated” in an elimination reaction
H and X
How is the rate of reaction dependent on the enthalpy of the C-X bond?
The greater the enthalpy of the C-X bond, the greater its strength, the slower the reaction
Which three nucleophiles do halogenoalkanes react with?
OH?, CN? and NH?
What reagents and conditions are necessary for a substitution of halogenoalkanes with hydroxide ions?
Reflux in warm, aqueous NaOH
What reagents and conditions are necessary for substitution of halogenoalkanes with cyanide ions?
Reflux in aqueous, alcoholic KCN
What is the importance of nucleophilic substitution with cyanide ions?
Increases the length of the carbon chain
What reagents and conditions are necessary for substitution of halogenoalkanes with ammonia?
Reflux in aqueous, alcoholic excess ammonia
Why is excess ammonia required in its nucleophilic substitution with a halogenoalkane?
To prevent further substitutions
What is the trend in C-X reaction rates?
Increases down the group from C-F to C-I
What is an elimination reaction?
A reaction where a halogenoalkane becomes an alkene
What conditions favour elimination reactions?
Reflux in hot, ethanolic NaOH
