Organic: Halogenalkanes Flashcards
what type of bonds do halogen alkenes contain
polar bonds due to highly electronegativity in the halogen compared to the carbon, causing a difference in electronegativity
give the uses for halogenalkanes
refrigerants -CFCs bad for environment
solvants
explain the classification of halogen alkanes H
H-C-Cl
H
primary- contains 1 R group
secondary- contains 2 R groups
tertiary- contains 3 R group
explain why halogenalkanes have boiling points than alkanes/alkenes even with the same molecular mass
they contain dipoles due to different electronegativity so the force of attraction between molecules are stronger than VdW forces in alkenes/alkanes so more energy is required to overcome
explain why the boiling point increases as we go down the halogen group
going down the group the molecule becomes larger so there are more e- meaning stronger VdW force/ increase in size so more energy is required to break down going down group 7
are halorgenalkanes soluble or not
they are not soluble since not polar enough to dissolve in water since they are not able to form hydrogen bonds with water and wont break dipole dipole and vdw forces of attraction
what doesa. curly arrow represent
the movement of a pair of electrons
where do arrows always start at in a mechanism
either, a lone pair or from the middle of a bond
if you make a bond
you must break a bond
give common examples of nucleophiles
OH- CN- NH3
why do we ignore the metals associated with nucleophiles
they are spectator ions
define a nucleophile
a species attracted to a positive by donating an electron pair
what two factors effect the rate of reaction of halogenalkanes
strength of the bond enthalpy
number of alkyl groups attracted to the c-x bond
which c-x bonds will have the slowest or fastest reaction rate
c-f has 484 bond enthalpy adn c-i has 238 bond enthalpy
going down the halogen group, the energy required to overcome the bonds decreases
so iodomethane will have the fastest reaction rate because the c-i bond is the weakest, less energy to overcome
Reactivity, rate, bond strength: rate the halogens going down the group
reactivity increasings
rate increases
bond strength decreases
give the two reactions that halogenalkanes undergo
nucleophilic substitution- A halogen atom is substituted by another atom or group of atoms forming alcohols, nitriles and amines.
elimination reactions- hydrogen halide is eliminated during the reaction and an alkene is produced
during elimination reaction using KOH what are the condiotions
hot concentrated and dissolved in ethanol
where does the elimination arriw go to
always from carbon which is next to the carbon that is bonded to halogen
aqueous conditions —- alcohol
OH- acts as a nucleophile donating ena electron pair SUBSTITUTION H-C-C-OH
anyhydrous conditions —- alkene
OH- acts as a base, accepts a H+ to form h20 ELIMINATION H-C=C-H
How do halogenoalkanes cause depletion of the ozone layer
Due to the strength of c-cl and c-f bonds its very unreactive, toxic and volatile, but the CFS undergo reactions of chlorine radicals with the ozone, decomposition atmosphere with UV radiation
CFC are volatile so if escaped they evaporate into atmosphere/stratosphere with more UV radiation exposed, forming more radicals
give the equations for ozone decomposition
Propagation step 1: Cl* + O3 → ClO* + O2
Propagation step 2: ClO* + O3 → 2O2 + Cl*
Overall equation: 2O3 → 3O2
scientists have found that using CH2F2, CHF3, C2H2F4 compounds wont threat ozone layer
they do not contain Cl so clorine radicals cannot form
define
halogenalkanes
nucleophilic reaction
elimination reaction
hydrolysis
Halogenoalkanes - a family of compounds that have had one or more hydrogen atoms in an alkane replaced by a halogen atom (these are also referred to as haloalkanes by some exam boards and some resources refer to them as alkyl halides)
Nucleophilic substitution - a reaction in which an electron-rich nucleophile displaces another atom or group of atoms
Elimination reaction - a reaction which involves the removal of a small molecule from one reactant molecule and produces two products
Hydrolysis - a reaction that involves water (or the aqueous solution of a hydroxide) that results in the breaking of a bond and the formation of two products
