Reactivity order, peroxides with

The reactivity of 02 - with alkyl halides in aprotic solvents occurs via nucleophilic substitution. Kinetic studies confirm that the reaction order is primary > secondary > tertiary and I > Br > Cl > F for alkyl hahdes, and that the attack by 02 - results in inversion of configuration (Sn2). Superoxide ion also reacts with CCI4, Br(CH2)2Br, CeCle, and esters in aprotic media. The reactions are via nucleophilic attack by 02 on carbon, or on chlorine with a concerted reductive displacement of chloride ion or alkoxide ion. As with all oxyanions, water suppresses the nucleophilicity of 02 (hydration energy, lOOkcalmoL ) and promotes its rapid hydrolysis and disproportionation. The reaction pathways for these compounds produce peroxy radical and peroxide ion intermediates (ROO and ROO ). 

The salt effect is small and positive, consistent with the attack of an ion on a neutral molecule. Allyl acetate has no effect on the rate or yield of product. Electron-releasing substituents accelerate the reaction. Thus the features of the reaction are similar to those of the Elbs reaction, and point to a mechanism involving nucleophilic attack of the amine on peroxide oxygen. In order to determine whether attack occurred by nitrogen or carbon, Behrman compared the rates of oxidation of amines such as 2-amino-5-methyl-pyridine and 2-amino-6-methyl-pyridine, and found that in all cases the order of reactivity is consistent with attack by nitrogen. Furthermore, the rate of oxidation of 3,5-dideutero-2-amino-pyridine is the same as for the normal material, and the yield of product is the same. Behrman proposed the reaction scheme... 

The choice of the oxidant is primordial, as it acts both as the nucleophile and the leaving group. A reactivity order of oxidants has been established [174]. Peracids and especially m-CPBA [296] are the most efficient oxidants for the Baeyer-Villiger reaction, followed by alkyl peroxides. The reaction with peracids proceeds faster under acid catalysis [297], but buffered solutions can also be used. Some ketones are un-reactive under standard conditions, and need to be transformed into their hemiketals [298]. Safer peracids such as MMPP (magnesium monoperphthalate) [299, 300] and sodium perborate [301] have also been applied giving similar results as m-CPBA. Recently, processes with solid-supported peracids [302] and transformations in the solid state [303] have been developed. 

The table below gives first-order rate constants for reaction of substituted benzenes with w-nitrobenzenesulfonyl peroxide. From these data, calculate the overall relative reactivity and partial rate factors. Does this reaction fit the pattern of an electrophilic aromatic substitution If so, does the active electrophile exhibit low, moderate, or high substrate and position selectivity ... 

Iodine can, however, be displaced cleanly with bromine<150) and with chlorine if iodine monochloride or sulfuryl chloride and benzoyl peroxide are used as chlorinating agents.reactivity ratios for the displacement of bromine by chlorine from substituted bromo-benzenes have been found to be in the order p-phenyl > o-methoxy > p-chloro > un-... 

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