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
Explain why the reaction between methanol and hydrochloric acid occurs according to the SN2 mechanism (see help)
