3.3 Halogenoalkanes
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Are halogenoalkanes soluble in water ?
They are insoluble as the C-H are non polar and the C-X bond doesn’t compensate enough.
Do halogenoalkanes have a polar bond ? Why ?
Yea, as the difference of electro negativity between C and X is large enough to form polar bonds between molecules.
What intermolecular forces do halogenoalkanes have ? Why ?
Permanent dipole-dipole and van der Waals forces C-X bond polarity creates permanent dipoles.
How do you increase the boiling point of halogenoalkanes ?
Increase the carbon chain length and increase the halogen size.
How would the mass of a haloalkane compare with the mass of an alkane of the same length ?
Haloalkane > halogen as all halogens are heavier than H.
What is the most important factor in determining the reactivity of a haloalkane ?
Carbon-Halogen bond enthalpy.
What is the most reactive and most unreactive haloalkane ?
Reactivity increases down the group as the C-F has the highest bond enthalpy.
What is a nucleophile ?
An electron dense / negative ion with a lone pair of electrons which can be donated to an electron deficient atom.
Give 3 examples of nucleophiles
OH- CN- NH3 All have lone pairs.
What is nucleophilic substitution ?
A reaction where a nucleophile donates a lone pair of electrons to d+ Carbon atom, d- leaves molecule which is replaced by the nucleophile.
What are CFCs ?
Chloro-fluorocarbons - halogens containing only C and X atoms.
What is the problems with CFCs ?
They are unreactive under normal conditions but UV light forms free radicals from CFCs and they deplete the ozone layer via free radical substitution.
What are the conditions + reactants needed for the elimination of haloalkanes
NaOH / KOH dissolved in ethanol High temperature.
What is formed in the elimination reaction of a haloalkane ?
An alkene, water and halogen ion.