Haloalkanes and Haloarenes 2 Flashcards
describe the colour of alkyl halides
Alkyl halides are colourless when pure. However, bromides and iodides
develop colour when exposed to light( due to release of I2 and Br2). Many volatile halogen compounds
have sweet smell.
describe the physical state of alkyl halides
Methyl chloride, methyl bromide, ethyl chloride and some
chlorofluoromethanes are gases at room temperature. Higher members
are liquids or solids.
why do halolalkanes have higher boiling points than their corresponding parent hydrocarbons?
molecules of organic
halogen compounds are generally polar. Due to greater polarity as well
as higher molecular mass as compared to the parent hydrocarbon, the
intermolecular forces of attraction (dipole-dipole and van der Waals)
are stronger in the halogen derivatives.
what is the order of increasing boiling point for R-X, for a given R
For the same alkyl group, the boiling
points of alkyl halides decrease in the order: RI> RBr> RCl> RF. This
is because with the increase in size and mass of halogen atom, the
magnitude of van der Waal forces increases.
relation between bpt of alkyl halides and branching
The boiling points of isomeric haloalkanes decrease with increase
in branching.
As branching increases the surface area of the molecule decereases and hence the magintude of the van der waals forces decreases.
comment of the bpt and mpts of dilahalobenzene?
Boiling points of isomeric dihalobenzenes are very nearly the same.
However, the para-isomers are high melting as compared to their orthoand meta-isomers. It is due to symmetry of para-isomers that fits in
crystal lattice better as compared to ortho- and meta-isomers.
The haloalkanes are very slightly soluble in water. justify
In order to dissolve
haloalkane in water, energy is required to overcome the attractions between
the haloalkane molecules( dipole-dipole attraction forces) and break the hydrogen bonds between water
molecules.
Less energy is released when new attractions are set up between
the haloalkane and the water molecules as these are not as strong as the
original hydrogen bonds in water. As a result, the solubility of haloalkanes
in water is low.
why are haloalkanes easily soluble in organic solvents
haloalkanes tend to dissolve in organic solvents
because the new intermolecular attractions between haloalkanes and
solvent molecules have much the same strength as the ones being broken
in the separate haloalkane and solvent molecules.
describe variation in density of haloalkanes
Bromo, iodo and polychloro derivatives of hydrocarbons are heavier than
water. The density increases with increase in number of carbon atoms,
halogen atoms and atomic mass of the halogen atoms
