Pyrimidine quatemisation

Other factors can influence the rate of quatemisation all the diazines react with iodomethane more slowly than does pyridine. Pyridazine, much more weakly basic (p/faH 2.3) than pyridine, reacts with iodomethane faster than the other diazines, a result which is ascribed to the a effect , i.e. the increased nucleophilicity is deemed to be due to electron repulsion between the two immediately adjacent nitrogen lone pairs. Reaction rates for iodomethane with pyridazine, pyrimidine and pyrazine are respectively 0.25,0.044 and 0.036, relative to the rate with pyridine. 

The quatemisation of a diazine naturally increases its propensity for addition of nucleophile for example, Reissert adducts have been described for pyri-dazine and pyrimidine. ... 

---

See also in sourсe #XX -- [ ]

---