substitution reactions

halogenoalkanes by free-radical substitution

alkanes react with chlorine or bromine in the presence of UV light

halogenoalkanes from electrophillic addition

alkenes react with halogens or hydrogen halides

halogenoalkanes by alcohol substitution

alcohols react with hydrogen halides, PCl3 under heat and PCl5 under room temperature

primary halogenoalkanes

halogen is bonded to carbon atom with only one alkyl group

secondary halogenoalkanes

halogen is bonded to carbon atom with 2 alkyl groups

tertiary halogenalkanes

halogen is bonded to carbon atom with 3 alkyl groups

general formula

CnH2n+1X

reactivity

decreases down the group…more reactive than alkanes due to polar nature between carbon and halogen atom

nucleophilic substitution

reaction in which a nucleophile attacks a carbon atom with a partial positive charge resulting in the replacement with an atom carrying a partial negative charge by the nucleophile

substitution reactions with aqueous alkali

halogen atom in the halogenoalkane is replaced by an OH- to form an alcohol

hydrolysis of a halogenoalkane

using reflux apparatus including a condenser and anti-bumping granules…halogenoalkane is broken down by water to form an alcohol, H+ and a halogen anion

fastest nucleophilic substitution

take place with iodalkanes

slowest nucleophilic substitution

take place with fluoroalkanes

substitution with cyanide ions in ethanol

use an ethanolic solution of potassium cyanide and heat under reflux with halogenoalkane…cyanide ion adds an extra carbon to carbon chain…forms halogen anion and newly formed chain

substitution with ammonia in ethanol

heated under pressure with excess ammonia dissolved in water…forms an amine and hydrogen halide