Organic Chemistry: Halogenoalkanes Flashcards
What is the general formula of halogenoalkanes?
CnH2n+1X
What is the functional group of halogenoalkanes?
C-X
Define a nucleophile
An electron pair donor
Why can halogenoalkanes take part in nucleophilic substitution?
Carbon-hydrogen bond in polar (halogen is more electronegative than carbon so carbon can accept electron pair)
What are the common nucleophiles?
Hydroxide ion (OH-)
Cyanide ion (CN-)
Ammonia (NH3)
How does nucleophilic substitution work?
The nucleophile donates a pair of electrons to the C
The C-H bond breaks due to heterolytic fission
A halide ion is formed
Halogenoalkanes and aqueous hydroxide reaction:
Products
Reagent
Conditions
General Equation
Products: Alcohol
Reagent: sodium hydroxide solution
Conditions: warm, aqueous
General Equation: R-X + OH- -> R-OH + X-
Halogenoalkanes and potassium cyanide reaction:
Products
Reagent
Conditions
General Equation
Products: Nitrile
Reagent: potassium cyanide
Conditions: ethanol, warm
General Equation: R-X + KCN -> R-CN + K-X
Halogenoalkanes and excess ammonia reaction:
Products
Reagent
Conditions
General Equation
Products: amine
Reagent: excess ammonia
Conditions: warm in a sealed tube, ethanol solvent
General Equation: R-X + 2NH3 -> R-NH2 + NH 4+X
Elimination
Products
Reagent
Conditions
Role
Products: Alkene
Reagent: NaOH/KOH
Conditions: Reflux in ethanol
Role: Base
What are the problems associated with CFCs?
Lead to a depletion of the ozone layer
How does ozone form in the upper atmosphere?
O2 + O· -> O3
Why are CFCs a harm to the ozone?
They breakdown to form chlorine radicals = catalyse the breakdown of ozone = lead to a hole in the ozone layer
Reaction of breakdown of CFCs
CCL3F -> ·CCl2F + ·Cl
Reaction of chlorine with ozone
·Cl + O3 -> O2 + ClO·
ClO· + O3 -> 2O2 + ·Cl
