Ozone Story - Halogen Reactions Flashcards
When will an alkane react with a halogen?
in the prescence of light
What are rates of reaction measured in?
mol dm-3 s-1
What are the 4 ways of measuring the rate of a reaction?
volume of gas produved
change in mass
change in pH
change of precipitate or colour
What is the Bolzmann distribution curve?
What is Ea?
activation enthalpy - the minimum amount of energy that reactants must have for a reaction to occur
If the temperature increases, what happens to the curve on a Bolzmann distribution curve?
the peak is lower and shifts to the right
What happens to the Ea on a Bolzmann curve if a catalyst is present?
it shifts to the left
What can rate of reaction be affected by?
temperature
concentration / pressure of reactants
intensity of radiation
particle size (in solids)
presence of a catalyst
What does CFC stand for?
chlorofluorocarbon
What are the properties of CFC in the troposphere?
non-toxic
non-flammable
very stable
very strong bonds
How can the overall result from a chain reaction be found?
add together the propogation steps
cancel any molecules that appear on both sides
What is the spectrum of bond strengths?
non-polar
polar
ionic
What is a pd-pd force?
permanent dipole - permanent dipole attraction
when the polar part of a molecule attracts the opposite polarity in another
What determines the strength of a polar bond?
How electronegative the elements are - the bigger the gap in electronegativity the more polar the bond
Why are symmetrical molecules not polar?
the forces cancel each other out
What are the features of an id-id force?
present in all molecules
weak force
depends on number of electrons present
branches reduces the effect
What are the features of pd forces?
can induce a pd-id force
forms pd-pd forces
only present in polar molecules
molecules have a higher melting/boiling point
stronger than id-id
What type of bond is stronger than pd-pd interaction?
hydrogen bonding
When will an id-id force be stronger than a pd-pd force?
if the molecules in the id-id force have significantly more electrons than the pd-pd molecules
What is a nucleophile?
something that can donate a pair of electrons to form a covalent bond
What type of molecule can be a nucleophile?
must have a non bonding pair of electrons
can be anions but not always
How are nucleophillic molecules usually represented?
:nuc-
What are the conditions for nucleophilic subsitution?
RTP
What is a disadvantage of nucleophilic substitution?
the atom economy wonโt be 100%
What happens during nucleophilic substitution with simple ions?
nucleophile is attracted to the ๐ฟ+ section of the molecule
this causes the on the ๐ฟ+ section to move to the ๐ฟ- section
simple ion bonds to the ๐ฟ+ section and ๐ฟ- section is given off as its own molecule
What are the reaction conditions for the production of HBr?
mix NaBr with phosphoric or sulfuric acid
heat under reflux
How can a haloalkane be converted into an alcohol?
nucleophilic substitution using water
How can an alcohol be converted into a haloalkane?
by adding a hydrogen halide
What are the 2 ways that haloalkanes can be produced?
adding a hydrogen halide to an alcohol
adding a hydrogen halide to an alkene
How can a haloalkane be converted into an amine?
nucleophilic substitution using NH3
What happens to the bond enthalpies of halogens as you go down the group?
the bond enthalpies get less exothermic
What are the reaction conditions for the nucleophilic substitution of a haloalkane using hydroxide ions?
use warm, aqueous sodium hydroxide
heat under reflux
What are the reaction conditions for the nucleophilic substitution of a haloalkane using ammonia?
warm the haloalkane with excess ethanolic ammonia (ammonia dissolved in ethanol)
heat under reflux
What are the reaction conditions for reacting haloalkanes with water?
add ethanol
add silver nitrate to see results
What is most important in a reaction - polarity or bond enthalpy?
bond enthalpy
What is the method for heating under reflux?
heat reagents in a round bottomed flask with a condenser vertically attached to it, so that evaporated products will condense and drip back down into the flask
