3.3.3 Halogenoalkanes Flashcards
Reactivity of halogenoalkanes
Much more reactive than alkanes
Uses of halogenoalkanes
Refrigerants,
Solvents
Pharmaceuticals
Are halogenoalkanes polar or non-polar
Polar due to high electronegativity difference between halogen atom and carbon it is bonded to
Nucleophile definition & 3 examples
‘Positive loving’ - an electron rich species that can donate a pair of electrons to form a covalent bond
:NH3
:OH-
:CN-
What makes more of a difference in halogenoalkane reactivity - bond enthalpy of electronegativity difference
Bond enthalpy, the larger the atom, the weaker the bond, so the lower the bond enthalpy. Iodine has fastest rate of reaction.
Conditions that favour substitution
Water solvent
Lower temperature
Lower conc of NaOH/KOH
Conditions that favour elimination
Ethanol solvent
Higher temperature
Higher conc of NaOH/KOH
Reflux
Carbocation definition
Hydrocarbon molecule in which one of its carbon atoms is only bonded to three other atoms and has a positive charge.
Elimination reaction definition
A reaction in which an atom or a group of atoms in a compound is removed from a molecule.
How does NaOH act as a nucleophile and a base
Base - Completely ionises water.
Nucleophile - it can donate a pair of electrons
What carbocation is the most stable
Tertiary as there is more of an inductive group due to 3 alkyl groups
tertiary > secondary > primary > methyl
Why is ozone beneficial
It absorbs ultraviolet radiation
What do CFC’s do
Form chlorine radicals which catalyse the decomposition of ozone
Depletion of ozone equations
Cl2 –> 2Cl*
Cl* + O3 –> ClO* + O2
ClO* + O3 –> 2 O2 + Cl*
