Peroxyacids conjugate acid

As in pyridine, it is the nitrogen in quinoline which undergoes protonation, alkylation, acylation and, with peroxyacids, oxidation to the A-oxide. S Ar reactions occur on the ring C-atoms, preferentially on those of the more activated benzene moiety. The relative reactivities of the individual heteroaromatic positions were determined by an acid-catalysed H-D exchange with D2SO4. This demonstrated that the SgAr process occurs via the conjugated acid, i.e. the quinolinium ion, and the positional selectivity C-8 > C-5/C-6 > C-7 > C-3 was observed. 

The rate of epoxidation of alkenes is increased by alkyl groups and other ERG substituents and the reactivity of the peroxy acids is increased by EWG substituents.72 These structure-reactivity relationships demonstrate that the peroxyacid acts as an electrophile in the reaction. Decreased reactivity is exhibited by double bonds that are conjugated with strongly electron-attracting substituents, and more reactive peroxyacids, such as trifluoroperoxyacetic acid, are required for oxidation of such compounds.73 Electron-poor alkenes can also be epoxidized by alkaline solutions of... 

Aldehydes and ketones are oxidized by the conjugate base of a peroxyacid to carboxylic acids and esters, respectively. 

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