2.Halogenoalkanes Flashcards
Halogen-Carbon bond strengths
C-F is the strongest and most polar.
C-I is the weakest and only slightly polar.
What are primary, secondary and tertiary halogenoalkanes?
primary: the carbon is bonded to one other alkyl group and so on.
Making halogenoalkanes?
Alkene + diatomic halogen, or HAlogen halide.
OR alkane free radical substitution.
Alkane free radical substitution reaction.
The halogen homolotically splits with UV to 2 free rads.
The Free red then reacts with a H, making a the chain a rad.
This carbon rad then bonds with a diatomic halogen, leaving the Halogen as the red.
Can continue to form di, tri,etc.
uses of halogenoalkanes?
anaesthetics Antiseptics Polermers (PVC) solvents (CFC's) fridges(CFC)
Why are CFC’s bad?
they are very stable, but at high altitude Uv light breaks them down, into chlorine radical and the rest of the chain rad.
This then catalyses the Ozone reaction(decompostion of Ozone one) so less uv gets absorbed
Whyare theyre many CFCS in the atmosphere?
still being released from fridges etc.
they also stay in the atmosphere a very long time, as they are stable.
hydrolysis of halogenoalkanes?
hga + OH- ions becomes a alcohol when the Oh replaces the halogen .
Under reflux.
Testing the rate of hydrolysis of halogenoalkanes?
hga is heated with aq silver nitrate and ethanol(to disolve everything) water has to be used as OH- would react with the AgNO3 . C-I is fastest , C-Cl slowest
What two factors effect rate of hydrolysis?and why
bond strength(enthalpy(more important))- as its the C-Halgen bond being broken. Polarity- C-F is more polar so the C should attract the neucleophile more readily.
alternatives to CFC’s
HCFCS- are non flammable and non toxic.
only a short term fix as it still depletes the Ozone.
Hydrolysis of branched halogenoalkanes?and primary teritary etc.
branched hydolysis faster
tertiary is faster as the primary bond is the strongest.
and tertiary is less stable.
