Chapter 15 - Haloalkanes Flashcards
Haloalkanes
- contain carbon, hydrogen and at least one halogen
how to name haloalkanes and prefixes
- order alphabetically (excl. di, tri, tetra etc…)
- fluoro
- chloro
- bromo
- iodo
primary, secondary, tertiary haloalkanes
primary - C attached to 2 H and one alkyl group
secondary - C attached to 1 H and two alkyl group
tertiary - C attached to no H and three alkyl group
Carbon - Halogen bond
- as halogens are more electronegative then carbon, carbon will be slightly positively charged and halogen will be slightly negatively charged
- bond is polar
- can act as nucleophiles
nucleophiles
- atom or grp/of atoms which are attracted to an electron deficient centre/atom where it donates a pair of electrons to form a covalent bond
- electron pair donor
nucleophile example
OH-
Br-
H2O
NH3
reaction mechanism
nucleophilic substitution
nucleophilic substitution
- when haloalkane reacts with nucleophile, nucleophile replaces halogen in substitution reaction
- undergone by primary haloalkanes with range of nucleophiles to produce a variety of compounds
Hydrolysis
- chemical reaction involving water or aqueous solution of hydroxide that causes the breaking of a bond in a molecule
- results in molecule being split into two products
nucleophilic substitution reactants, products and conditions
- haloalkane and nucleophile
- alcohol and halide ion
- NaOH & heat under reflux
what else do haloalkanes react with
water - slower reaction then with hydroxide ions
H3CX + H2 –> H3COH + HX
reactivity of haloalkanes
- as you go down the group the haloalkanes become more reactive
- due to bond enthalpy decreasing as atoms are less electronegative going down the group so bonds are weaker
how to test reactivity of haloalkanes
add AgNO3 and record the rate of which the precipitate forms
Organohalogens
compounds that have at least one halogen atom joined to a carbon chain
what are organohalogens used as
refrigerants, flame retardants, solvents and to make polymers
what is ozone
O3
- found in outer layer of the stratosphere
what happens to ozone naturally?
UV radiation splits it into atoms
O2 –> 2O
it then reacts with molecules to form ozone (actually a reversible reaction
O2 + O –> O3
how are chlorine radicals formed
by UV radiation
Cl2 –> .Cl
what are CFC’s?
Chlorofluorocarbons
contain chlorine, fluorine and carbon atoms
what happens as the ozone layer is depleted
more UV radiation can reach the earth
what are CFCs used for
refrigerants, air conditioning units, aerosol propellants
effects of UV radiation
- aging skin generally
- skin cancer
- sun burn
ozone layer depletion
(with chlorine)
Propagation step 1: .Cl + O3 –> ClO. + O2
Propagation step 2: ClO. + O –> .Cl + O2
Overall eq.: O3 + O –> 2O2
ozone layer depletion
(with nitrogen oxides)
Propagation step 1: NO. + O3 –> NO2. + O2
Propagation step 2: NO2.+ O –> NO. + O2
Overall eq.: O3 + O –> 2O2
