Interhalogen monofluorides (XF; X=Cl, Br or I) generated in situ from hypohalites or N-halosuccinimides and a source of fluoride ion are "sluggish" electrophiles. XF reagents formed from F2 gas and a halogen source (ie: ClF3, Br2, I2,) are very reactive electrophiles. This wide
range of reactivity allows the synthetic chemist to carry out reactions on electron-rich or electron-deficient substrates. Halofluorinations of alkenes, alkynes and electrophilic aromatic substitution without catalyst are reviewed. Synthesis of geminal difluorides from hydrazones is also presented.