Electrophilic Halogenation - Scope

Scope

If the ring contains a strongly activating substituent such as -OH, -OR or amines, a catalyst is not necessary, for example in the bromination of p-cresol:

However, if a catalyst is used with excess bromine, then a tribromide will be formed.

Halogenation of phenols is faster in polar solvents due to the dissociation of phenol, with phenoxide ions being more susceptible to electrophilic attack as they are more electron-rich.

Chlorination of toluene with chlorine without catalyst requires a polar solvent as well such as acetic acid. The ortho to para selectivity is low:

No reaction takes place when the solvent is replaced by tetrachloromethane. In contrast, when the reactant is 2-phenyl-ethylamine, it is possible to employ relatively apolar solvents with exclusive ortho- regioselectivity due to the intermediate formation of a chloramine making the subsequent reaction step intramolecular.

The food dye erythrosine can be synthesized by iodination of another dye called fluorescein:

This reaction is driven by sodium bicarbonate.

Read more about this topic:  Electrophilic Halogenation

Famous quotes containing the word scope:

    In the works of man, everything is as poor as its author; vision is confined, means are limited, scope is restricted, movements are labored, and results are humdrum.
    Joseph De Maistre (1753–1821)

    Happy is that mother whose ability to help her children continues on from babyhood and manhood into maturity. Blessed is the son who need not leave his mother at the threshold of the world’s activities, but may always and everywhere have her blessing and her help. Thrice blessed are the son and the mother between whom there exists an association not only physical and affectional, but spiritual and intellectual, and broad and wise as is the scope of each being.
    Lydia Hoyt Farmer (1842–1903)

    The scope of modern government in what it can and ought to accomplish for its people has been widened far beyond the principles laid down by the old “laissez faire” school of political rights, and the widening has met popular approval.
    William Howard Taft (1857–1930)