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?
Haloalkane: Nucleophilic substitution reaction
Nucleophilic substitution reaction The reaction in which a nucleophile replaces already existing nucleophile in a molecule is called nucleophilic substitution reaction. * Nucleophiles are electron rich species so they attack at that part of substrate molecule which is electron deficient. Ambident Nucleophiles Nucleophiles which can attack through two different sites are called ambient nucleophiles. Eg- Cyanide ion exists as hybrid of following two structures. It can attack either through carbon to form cyanides or through nitrogen to form isocyanides. Q Haloalkanes react with KCN to form alkyl cyanide as major or main product while AgCN forms isocyanide as the chief product. explain. Ans- KCN is ionic and provide cyanide ion in solutions. Both carbon and nitrogen atoms are in a position to donate electron pairs. The attack takes place mainly through carbon atom and not through nitrogen atoms since C-C bond is more stable than C-N bond. A
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