Haloalkanes: Classification
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Depression in freezing point
Depression in freezing point Graph Freezing point :-> Freezing point is defined as the temperature at which the vapour pressure of the solid solvent is equal to the vapour pressure of liquid solvent. Depression in freezing point :-> The difference in the Freezing point of pure solvent and the freezing point of Solution is called depression in freezing point. Freezing point depression constant
Haloalkane: physical properties
Physical state * 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. in this figure, 2-bromo-2-methyl propane has the lowest boiling point. Q The boiling point decreases with the increase in branching. why?
Amines: Arylamines versus ammonia
Q Why pkb value of aniline is quite high? Ans- Because in aniline or other Arylamines,the -NH2 group is attached directly to the benzene ring . The lone pair of electrons on the nitrogen atom is delocalised over the benzene ring. As a result, the electron density on the nitrogen atom decreases. so, aniline is weaker base and its pkb value is higher than of methylamine. Q Which is more stable aniline or anilinium ion? Ans- Greater the number of resonating structures greater is the stability. Aniline has five resonating structures and anilinium has two resonating structures. So, aniline is more stable than anilinium ion. So, basic nature of aniline or other aromatic amine is less than of ammonia.
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