* Alkyl halides are colourless in pure condition.
* Bromides and iodides develop colour when exposed to light.
* Many volatile halogen compounds have sweet smell.
Boiling point
Q Haloalkanes have higher boiling point than corresponding comparable molecular mass of hydrocarbon. why?
Ans- This is due to haloalkanes are generally polar due to dipole dipole interaction and vander wall forces haloalkanes have higher boiling point than hydrocarbon.
Q Boiling point of alkyl halide decreases in order as RI < RBR < RCL < RF. Why?
ANS- This is because with the increase in size and mass of halogen atom, the magnitude of vander wall forces increases. So, boiling point of alkyl halides decreases.
* Boiling point of isomeric haloalkane
Boiling point of isomeric haloalkanes decreases with increase in branching.
Q The boiling point decreases with the increase in branching. why?
Ans- This is due to decrease in magnitude of London force of attraction. So, a branched chain isomers will have lower boiling point than straight chain isomers.
Melting point
Q Melting point of paradichlorobenzene are high as compared to their ortho and meta isomers.why?
Ans- It is due to symmetrical structure of para isomers that fits into crystal lattice then compared to ortho and meta isomers.
Density
Density of haloalkanes is heavier than water. Density increases with increase in carbon atom, resulting increase in molecular size.
Solubility
Q Haloalkanes are very slightly soluble in water. Why?
Ans- This is due to following reasons:-
(a) Energy is necessary to overcome the attraction between the haloalkane molecules and break the hydrogen bonds between water molecules.
(b) 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.
(c) Due to this haloalkanes are soluble in most of the organic solvent.
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