Nucleophilic attacks on alcohols

The nucleophilic attack Nucleophiles Molecules or ions having an atom with a free doublet capable of binding to an electrophilic atom or a cation.

Nucleophilic character of halide ions

- The nucleophile character increases from top to bottom in a periodic table family:

... because in the larger atoms the outer electrons are less well held because of the larger distance from the nucleus.

Nucleophilic attack of a halogenated hydracid on an alcohol: The halogenated hydracids $(HF, HCl, HBr, HI) $ dissociate in water by releasing $ H^+ $ and $ F^-, Cl^-, Br^- $ or $ I^- $ nucleophilic ions. ! The $ H^+ $ ions activate the alcohol by fixing on its $ O $ atom, then two mechanisms can occur, for example:

The preponderance of one or the other of these mechanisms depends essentially on the stability of the cation $ A $ that could be formed during the second mechanism