( ii) Reaction involving cleavage of C-O bond in alcohols In these reactions, the reactivity order of different alcohols:
Alkyl group due to + 1 effect increases the electron density on the carbon and oxygen atom of C-OH bond. As a result, the bond cleavage becomes easy. Greater the number of alkyl groups present, more will be the reactivity of alcohol. Thus, the relative order of reactivity of the alcohols is justified.
Reaction with halogen acids
Alcohols can be converted into haloalkanes by the action of halogen acids.
R – OH + HX( HCI, HBr, HI) → R-X + H2O
For a given alcohol order of reactivity of HX is
H-1 > H-Br > H-Cl
For a given halogen acid order of reactivity of alcohols
Tertiary > Secondary > Primary