Explain fully the physical properties of ...-
A . Haloalkanes
B. Haloarenes
Explain fully the physical properties of ...-
A . Haloalkanes
B. Haloarenes
A)Haloalkanes Physical properties of any compound depend largely on
- Its mass
- The type of intermolecular and intramolecular forces of attraction
Melting Point and Boiling Point of haloalkanes
There is large electronegativity difference between halogens and carbon resulting in highly polarized molecules. The higher molecular mass and greater polarity as compared to the parent hydrocarbon results in stronger intermolecular forces of attraction (dipole-dipole and van der Waals) in the halogen derivatives. Boiling Point depends upon the intermolecular forces of attraction and hence the boiling points of chlorides, bromides and iodides are considerably higher than those of the hydrocarbons of comparable molecular mass. As we go down in homologues series of haloalkanes, the forces of attraction becomes stronger due to increase in molecular size and it’s mass, hence the boiling point increases down the homologues series. But the boiling point decreases with branching.
Methyl chloride, methyl bromide, ethyl chloride and some chlorofluoromethanes are gases at room temperature. Higher members are liquids or solids.
Density of haloalkanes
Density is directly proportional to the mass of compound, hence down the homologous series, density increases, also fluoro derivatives are lesser dense than chloro derivatives; chloro derivatives are less dense than bromo derivatives and so on.
Solubility of haloalkanes
Haloalkanes are slightly soluble in water. This is because of the relatively larger amount of energy required to break bond between halogen and carbon and the smaller amount of energy released, when bond is formed after dissolution ion and water.
B) PHYSICAL PROPERTIES OF HALOARENES 1. Boiling points
The boiling points of monohalogen derivatives of benzene, which are all liquids, follow the order
Iodo > Bromo > Chloro
The boiling points of isomeric dihalobenzenes are nearly the same. However, their melting points are quite different. The melting point of para isomer is generally70-100 degrees higher than the melting points of ortho and meta isomers. The higher melting point of para isomer is due to its symmetry which leads to more close packing of its molecules in the crystal lattice and consequently strong intermolecular attractive forces.
2. Solubility
Haloarenes are insoluble in water, acids or bases but are soluble in organic solvents.
Haloarenes are insoluble in water because they cannot form hydrogen bonds with water molecules.
3. Density
These are all heavier than water. Their densities follow the order.
Physical properties of any compound depend largely on
- Its mass
- The type of intermolecular and intramolecular forces of attraction
Melting Point and Boiling Point of haloalkanes
There is large electronegativity difference between halogens and carbon resulting in highly polarized molecules. The higher molecular mass and greater polarity as compared to the parent hydrocarbon results in stronger intermolecular forces of attraction (dipole-dipole and van der Waals) in the halogen derivatives. Boiling Point depends upon the intermolecular forces of attraction and hence the boiling points of chlorides, bromides and iodides are considerably higher than those of the hydrocarbons of comparable molecular mass. As we go down in homologues series of haloalkanes, the forces of attraction becomes stronger due to increase in molecular size and it’s mass, hence the boiling point increases down the homologues series. But the boiling point decreases with branching.
Methyl chloride, methyl bromide, ethyl chloride and some chlorofluoromethanes are gases at room temperature. Higher members are liquids or solids.
Density of haloalkanes
Density is directly proportional to the mass of compound, hence down the homologous series, density increases, also fluoro derivatives are lesser dense than chloro derivatives; chloro derivatives are less dense than bromo derivatives and so on.
Solubility of haloalkanes
Haloalkanes are slightly soluble in water. This is because of the relatively larger amount of energy required to break bond between halogen and carbon and the smaller amount of energy released, when bond is formed after dissolution ion and water.
B) PHYSICAL PROPERTIES OF HALOARENES1. Boiling points
The boiling points of monohalogen derivatives of benzene, which are all liquids, follow the order
Iodo > Bromo > Chloro
The boiling points of isomeric dihalobenzenes are nearly the same. However, their melting points are quite different. The melting point of para isomer is generally70-100 degrees higher than the melting points of ortho and meta isomers. The higher melting point of para isomer is due to its symmetry which leads to more close packing of its molecules in the crystal lattice and consequently strong intermolecular attractive forces.
Haloarenes are insoluble in water, acids or bases but are soluble in organic solvents.
Haloarenes are insoluble in water because they cannot form hydrogen bonds with water molecules.
3. Density
These are all heavier than water. Their densities follow the order.
